Dissertations / Theses on the topic 'Collapse of the soil'

Collapse phenomenon is exhibited by two types of residual soils. The first category of collapsing residual soils is believed to be transported soils that have undergone post-depositional pedogenesis. The second category of collapsing residual soils is highly weathered and leached soils formed by in-situ weathering of parent rock. Residual red soils occur in Bangalore District of Karnataka State. Physical and chemical weathering of the gneissic parent rock formed the residual soils of Bangalore District. The red soils of Bangalore District are generally moderate to very highly porous (porosity range 35-50%). These soils are also unsaturated owing to presence of alternate wet and dry seasons and low ground water table. Moderately to highly porous, unsaturated red soils occur in Pernambuco State of Brazil. These residual soils formed by weathering of gneissic rock significantly collapse on wetting under external pressures. Kaolinite is predominant clay mineral in the red soils of Bangalore and Pernambuco Districts. Similarities exist in the mode of soil formation, clay mineralogy, porosity and degree of saturation (Sr) values of the red soils from Pernambuco State, Brazil, and Bangalore District. Given the collapsible nature of red soils from Pernambuco State, Brazil, the red soils from Bangalore District also deserve to be examined for their potential to collapse in the compacted and undisturbed conditions. The roles of initial dry density, compaction water content, clay content and flooding pressure (the external stress at which a laboratory specimen is inundated is termed as flooding pressure in this thesis) in determining the collapse behaviour of compacted soils are well recognized. However, the influences of above parameters on the collapse behaviour of compacted red soil specimens from Bangalore District are lacking. Such studies are essential as they help to identify the critical compaction parameters (dry density and water content), soil composition, and applied stress level that needs to be controlled by the fill designer in order to minimize wetting-induced collapse. The importance of matric suction in the collapse behaviour of unsaturated soils is well recognized. Yet, the influence of matric suction in the collapse behaviour of compacted soils has only been indirectly examined by varying the compaction water content/degree of saturation of the soil specimens. The climate of Bangalore District is characterized by alternate wet and dry seasons which affects the soil microstructure and the matric suction. Both these parameters have a significant influence on collapse behaviour of unsaturated soils. Cyclic wetting and drying is expected to have a significant bearing on the collapse behaviour of residual soils and is therefore examined. The red soil deposits of Bangalore District are important from foundation engineering view point as they are subjected to structural loading. Owing to the presence of alternate wet and dry seasons and low ground water table, red soil deposits of Bangalore District are more often than not unsaturated. These foundation soils would however be susceptible to increase in moisture content from causes such as infiltration of rainwater, leakage of pipes or watering of lawns and plants. Given the porous and unsaturated nature of undisturbed red soils from Bangalore district, their collapsible nature deserves to be examined for reliable estimation of foundation settlements. To achieve the above objectives, experiments are performed that study: 1.The influence of variations in compaction dry density, initial water content and matric suction, clay content and flooding pressure on the collapse behaviour of a representative red soil sample from Bangalore District. 2.The influence of repeated wetting and drying on the collapse behaviour of compacted red soil specimens. 3.The collapsible nature of undisturbed red soil samples from different locations in Bangalore District. The organization of this thesis is as follows: After the first introductory chapter, a detailed review of literature highlighting the need to study the collapse behaviour of unsaturated red soils of Bangalore District, Karnataka in the compacted and undisturbed states comprises Chapter 2. Chapter 3 presents a detailed experimental programme of the study. Details of representative and undisturbed red soil samples from Bangalore District, Karnataka State, India were used in the study are provided. Determination of collapse potential of compacted and undisturbed soil specimens using conventional oedometer is discussed. Determination of matric suction of compacted and undisturbed specimens by ASTM Filter paper method and pore size distributions by mercury intrusion porosimetry is detailed. Methods to perform cyclic wetting and drying of compacted red soil specimens in modified oedometer assemblies is detailed. These experiments are performed to examine the influence of cyclic wetting and drying on the collapse behaviour of compacted red soil specimens. Chapter 4 examines the collapse behaviour of a compacted red soil from Bangalore District. The influence of variations in compaction dry density, initial water content and matric suction, flooding pressure and clay content on the collapse behaviour of the representative red soil from Bangalore District are examined. Besides measuring the initial matric suction of the compacted red soil specimens, mercury intrusion porosimetry was performed on selected compacted red soil specimens. Experimental results showed that compacted red soils from Bangalore District exhibited tendency to swell and collapse at the experimental range of densities and water contents. Red soil specimens compacted to relative compactions > 90 % at water contents below OMC swelled at flooding pressures lower than 200 kPa. Red soil specimens compacted to relative compactions < 90 % at water contents below OMC significantly collapsed at flooding pressures larger than 200 kPa. Hence maintenance of the design water content during construction of compacted red soil fills is essential to minimize wetting induced volume changes. Experiments showed that the relative abundance of coarse pores (60 to 6 μm, pore radius) were mainly affected on increasing the relative compaction of the specimens from 84 % (dry density = 1.49 Mg/m3) to 100 % (dry density = 1.77 Mg/m3). The relative abundance of the coarse and fine (0.01 to 0.002 μm) pores were both affected on increasing the compaction water content from 10.6 to 26.4 %. These variations in pore size distributions provided better insight into the variations of collapse potential with variations in compaction parameters. ASTM filter paper method showed that for the selected compaction conditions the initial matric suction of the compacted red soil specimens varied between 60 and 10,000 kPa. Further, variations in degree of saturation at a constant relative compaction or variations in relative compaction at a constant degree of soil saturation notably affected the matric suction of the compacted soil specimens. It was also inferred that a clay soil with a higher liquid limit is characterized by a higher matric suction at a given water content. Variations in clay content affected the collapse potentials of soil specimens compacted to dry densities of 1.49 and 1.66 Mg/m3. These specimens exhibited maximum collapse at about 26 % clay content. It is suggested that greater destabilization of inter-particle contacts caused by loss of matric suction on flooding was primarily responsible for the soil specimen containing the critical clay content of 26 % to exhibit maximum collapse potential. Increase in initial dry density, initial water content, clay content of the soil specimen and flooding pressure increased the time-duration of collapse of the compacted soil specimens. The time-duration of collapse was observed to range between 3 and 100 minutes for the tested specimens. Chapter 5 examines the influence of alternate wetting and drying on the collapse behaviour of compacted red soil specimens of Bangalore District. The compacted specimens were subjected to alternate wetting and drying cycles at surcharge pressures of 6.25 and 50 kPa in modified oedometer assemblies. Studies were also performed to examine whether the initial placement conditions have any bearing on the collapse behaviour of red soil specimens subjected to four cycles of wetting and drying. Mercury intrusion porosimetry was performed on a few desiccated red soil specimens. Experimental results showed that cyclic wetting and drying caused the desiccated specimens to exhibit similar or lower swell and collapse potentials than the compacted specimens. Such a behaviour resulted despite the desiccated specimens (specimens subjected to four cycles of wetting and drying are termed as desiccated specimens) possessing similar void ratios but much lower water contents than the compacted specimens. The restraining influence of the desiccation bonds and alteration of soil structure is considered responsible for the reduced swell and collapse tendencies of the desiccated specimens. The desiccation bonds imparted higher apparent preconsolidation pressures to the desiccated specimens. The initial compaction conditions also have a strong bearing on the collapse potentials of the desiccated specimens. Compacted red soil specimens subjected to cyclic wetting and drying under a higher surcharge pressure of 50 kPa exhibited larger swell potentials and lower collapse potentials than specimens desiccated at 6.25 kPa. Besides their lower void ratios, the presence of stronger desiccation bonds also contributed to their lower collapse potentials. The presence of stronger desiccation bonds in specimens desiccated under higher surcharge pressure was indicated by their higher apparent preconsolidation pressures. Chapter 6 examines the collapse behaviour of undisturbed red soil specimens from three locations in Bangalore District at a range of flooding pressures. Studies on the variations in initial water content and effect of remoulding on the collapse behaviour of the undisturbed specimens is supplemented by measuring the initial matric suction and performing mercury intrusion porosimetry experiments. Experimental results showed that based on their collapse potential at 200 kPa, the undisturbed red soils of Bangalore District classified as troublesome to moderately troublesome foundation soils. The bonded structure of the undisturbed red soil specimens imparted them higher apparent preconsolidation pressures and lower swell/collapse potentials than their remoulded counterparts. Variations in in-situ dry density, degree of saturation and relative distribution of pore sizes affected the matric suction and collapse potentials of the undisturbed specimens Chapter 7 summarizes the conclusions of this thesis.

A field test is developed to assess the collapse susceptibility of soils rapidly and inexpensively. The in situ collapse test device measures the vertical deformations which occur in soils when they are subjected to stress and given access to water while under continuous load. Principles of statistics were employed to show that laboratory testing of soil specimens overestimate the magnitude of collapse as measured in the field and that the magnitude of collapse is, in part, a function of the soil moisture content at the time of loading and at the time of collapse. Good correlation was found between the spatial variability of collapsible soils with the location of alluvium terrace deposits and structurally damaged buildings.

In this thesis, previous research works on the collapse analysis of underground excavations: tunnels, trapdoors and plane strain headings, are reviewed. Through the discussion of the collapse of a single circular tunnel in soil, the collapse mechanism of two parallel circular tunnels is established under the condition of Tresca yield criterion. Employing the bound theorems of plasticity theory, admissible velocity fields and admissible stress fields are created around the two tunnels to obtain upper and lower bound solutions. The bound solutions for two parallel circular tunnels are compared with the test results from a centrifuge experiment in literature. Several new parameter definitions: field stability ratio N[, natural stability ratio Nn , external stability ratio Ne, collapse stability ratio Nc and the stability analysis line (SAL) are introduced. A new stability analysis plot is derived to analyse the collapse of geotechnical structures, working with the finite element software package - CRISP. According to the stability state of tunnels in soil, five principal procedures for searching for the collapse stability ratios are developed, based on the stability analysis plot. Under the condition of soil with self weight, the stability ratios for the two tunnels obtained from the finite element method agree well with the solutions obtained using the bound theorems. Two models of three-dimensional trapdoors, square and rectangular trapdoors, are developed to investigate local roof collapse in twmels. Comparing several trapdoor stability solutions, it is proposed that different trapdoor models (3D block, 3D rectangular and 3D square models) can be used to the stability analysis for the square trapdoors located in different depths. The upper and lower bound solutions for square and rectangular trapdoors are derived and discussed. Block Analysis Method with a triangular element is developed to examine the stability of a vertical cut and a plane strain heading. The interfaces between two blocks are treated as elements, while the blocks are treated as extended nodes. The force equilibrium equations of a soil structure and yield criterion equations are assembled into a linear programming that is solved with the Simplex Method to obtain optimum stability ratio, via the load factor. This method shows good potential for the collapse analysis of soil structures in geotechnical engineering practice in the future.

Thesis (Civ. E.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 137-138).
This thesis re-analyzes the well-documented failure of a 30m deep braced excavation underconsolidated marine clay. Prior analyses of the collapse of the Nicoll Highway have relied on simplified soil models with undrained strength parameters based on empirical correlations and piezocone penetration data. In contrast, the current research simulates the engineering properties of the key Upper and Lower Marine Clay units using a generalized effective stress soil model, MIT-E3, with input parameters calibrated using laboratory test data obtained as part of the post-failure site investigation. The model predictions are evaluated through comparisons with monitoring data and through comparisons with results of prior analyses using the Mohr-Coulomb (MC) model. The MIT-E3 analyses provide a modest improvement in predictions of the measured wall deflections compared to prior MC calculations and give a consistent explanation of the bending failure in the south diaphragm wall and the overloading of the strut-waler connection at the 9th level of strutting. The current analyses do not resolve uncertainties associated with performance of the JGP rafts, movements at the toe of the north-side diaphragm wall or discrepancies with the measured strut loads at level 9. However, they represent a significant advance in predicting excavation performance based directly on results of laboratory tests compared to prior analyses that used generic (i.e., non site-specific) design isotropic strength profiles.
by Gonzalo Andrés Corral Jofré.
Civ.E.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Large areas of the earth’s surface are covered by soils that are susceptible to large decreases in bulk volume when they become saturated. These soils are termed collapsing soils and are very common in parts of the USA, Asia, South America and Southern Africa. This study is concerned with the occurrence of these collapsible soils in the residual granites of the Stellenbosch area. The study was undertaken as relatively little is known about the collapse phenomenon in the problematic weathered granites of the Western Cape. The majority of research thus far has been carried out on the deep residual soils formed on basement-granite in the Transvaal areas, whereas little attention has been paid to the Cape granites. The aim of the study was achieved through the experimental work which included double oedometer testing, indicator analyses and shear strength testing. Double oedometer tests were performed to quantify the potential collapse settlement of the soils from the demarcated study area. To provide a better understanding of the collapse behaviour of the soils, indicator analysis, which included Atterberg limits and particle size distributions, were performed. Direct shear tests were further carried out on saturated and natural moisture content specimens to establish the effect of collapsibility on shear strength and whether substantial additional settlement of the saturated soils would occur during shear. It was found that collapsible soils are prevalent in the demarcated study area as the majority of soils showed a potential collapse settlement of 1% or more. Collapse exceeding 5% were calculated in a few instances proving some soils to be highly collapsible. The double oedometer and indicator analysis results were used in an attempt to obtain a relationship between collapse settlement and a combination of easily determined properties such as dry density (void ratio), moisture content and grading, but no meaningful conclusions have emerged. The shear strength tests indicated that a clear correlation does not exist between collapsibility and shear strength. It was further established that a relationship between collapse settlement determined during the double oedometer testing and the volume change during shear strength testing cannot be assumed. It can thus be concluded that soils can be very unpredictable and further research on the collapse phenomenon is indicated.
AFRIKAANSE OPSOMMING: Groot dele van die aarde se oppervlakte is bedek deur grondtipes wat geneig is tot ‘n afname in volume as dit deurweek word. Hierdie gronde word swigversakkende gronde genoem en dit word algemeen teëgekom in dele van die VSA, Asië, Suid-Amerika en Suider-Afrika. In hierdie studie word die voorkoms van swigversakkende gronde in die residuele graniet in die Stellenbosch area ondersoek. Die studie is onderneem aangesien relatief min i.v.m. die swigversakking-verskynsel in die problematiese verweerde graniet van die Weskaap bekend is. Die meeste van die navorsing sover is onderneem op die diep residuele gronde wat gevorm is op die Argaïese graniet in die Transvaal gebied, en betreklik min aandag is geskenk aan die Kaapse graniet. Tydens die studie is eksperimente wat dubbele oedometer toetse, indikator analises, en skuifsterkte toetse insluit, uitgevoer. Dubbele oedometer toetse is uitgevoer om die potensiële swigversakking van die grond in die afgebakende studiegebied te kwantifiseer. In ‘n poging om die swigversakking-verskynsel van die grond beter te verstaan, is indikator analises wat Atterberg grense en partikel grootte verspreiding insluit, uitgevoer. Direkte skuiftoetse is ook uitgevoer op deurweekte grondmonsters en op monsters wat natuurlike vog bevat, om sodoende die effek van swigversakking op skuifsterkte vas te stel en om uit te vind of aansienlike addisionele sakking van die deurweekte gronde tydens skuif plaasvind. Daar is gevind dat swigversakkende gronde die oorheersende grondtipe in die afgebakende studiegebied is waar meeste van die gronde ‘n potensiële swigversakking van meer as 1% toon. ‘n Swigversakking van meer as 5% is in ‘n paar gevalle bereken, wat bewys dat sommige grondtipes hoogs versakkend is. Die resultate van die dubbele oedometer en indikator analises is gebruik in ‘n poging om te bewys dat daar ‘n verhouding bestaan tussen swigversakking en ‘n kombinasie van kenmerke wat maklik vasgestel kan word soos droë digdheid (ruimte verhouding), voginhoud en gradering, maar daar kon nie tot ‘n sinvolle slotsom gekom word nie. Die skuifsterkte toetse toon dat daar nie ‘n duidelike korrelasie bestaan tussen swigversakking en skuifsterkte nie. Daar is verder vasgestel dat dit nie moontlik is om te aanvaar dat daar ‘n verhouding bestaan tussen swigversakking soos vasgestel tydens die dubbele oedometer toetsing, en die verandering in volume tydens skuifsterkte toetsing nie. Daar is dus tot die slotsom gekom dat grond baie onvoorspelbaar kan wees en dat verdere navorsing na die swigversakking-verskynsel nodig is.

Insufficient information on the host medium can cause serious problems, even collapse, during construction in a tunnel. This study focuses on understanding the reasons behind the collapse of the Tunnel BT24 to be opened within the framework of Ankara-Istanbul High Speed Railway Project. The tunnel is located near Bozü
yü
k in the Bilecik Province. The collapsed section of the tunnel was driven into a highly weathered, weak to medium rock mass. Unanticipated geological/geotechnical circumstances caused excessive deformations at the section on which the primary support system was applied, leading eventually to collapse. To understand the response of the tunnel and the collapse mechanism, the construction sequence is simulated using two-dimensional plane-strain and axisymmetric finite element models. The analyses were carried out for the section with and without invert closure of the shotcrete liner. To implement the effects of likely unfavorable ground conditions on the tunnel response, a number of fault scenarios and possible creep effects were also considered with those two alternatives. Displacements in the tunnel periphery, forces and moments in the primary liner as well as the plastic deformation zones in the surrounding ground were determined for each case and comprasions were made accordingly. It is concluded that the unforseen ground circumstances might have substantially aggravated the deformations in the section and that the lack of ring closure of the primary liner at invert played the key role in the collapse.

Unsaturated compacted soils are used in many civil engineering works, such as earth dams, embankments, soils beneath foundations and pavements. A major problem encountered with these soils is the tendency to collapse upon wetting under certain conditions. There has been extensive research into the collapsibility of compacted soils. However, comprehensive investigation into the hydro-mechanical behaviour of unsaturated compacted soils under various loading, wetting and compaction conditions is needed for the engineers to devise safe and cost-effective solutions to such problem. The outcomes of such a study also provides a wider perspective on soil collapsibility and generate geotechnical data and parameters useful for establishing and validating constitutive models. This thesis presents a laboratory-based experimental study of the collapse behaviour of compacted soil mixtures of 40% silt, 40% sand and 20% clay. Series of laboratory tests were conducted including basic characterisation, static compaction behaviour, suction measurements, single and double-oedometer tests, and suction-controlled oedometer tests under wetting. In this context, a new static compaction testing procedure is developed for establishing static compaction curves of the soil both in terms of applied compaction pressure and compaction energy. One-dimensional volume change behaviour of compacted samples along the established static compaction curves was explored. Statically compacted specimens with various compaction conditions were subjected to a wide range of vertical stresses. The compatibility of various controlled-suction wetting tests was also explored. The experimental data obtained were analysed in terms of collapse strain and soil-water characteristic curves (SWCC) based on theories of unsaturated soil mechanics. The proposed procedure of the static compaction tests showed the potential effectiveness in establishing static compaction curves at various levels of compaction energy and pressure. The static compaction pressure required to transmit constant compaction energy was found to decrease with increasing the water content of specimens, whereas increased compaction energy was observed along the compaction pressure curves. The static compaction was also found to induce suction changes of specimens. The study generated new knowledge in the form of linking the compaction effort with the collapse behaviour at a various range of applied vertical stresses and suction. The collapse behaviour of compacted specimens along the static compaction curves was found to be predominantly controlled by the applied compaction pressure during specimen preparation. Similarly, the wetting SWCCs of compacted specimens along the static compaction curve were found to be strongly influenced by the static pressure of compaction at low suctions.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Neste trabalho se analisam as características de colapso de um solo laterítico submetido à percolação de um licor cáustico a diferentes concentrações. O solo é uma areia quartzosa com uma pequena fração de finos cauliníticos. O licor é um efluente industrial, resultante da produção de alumínio, a base de soda cáustica. Mediante o presente estudo, determinou-se o efeito da infiltração do licor cáustico sobre três aspetos: colapsividade, transporte de solutos e características de sucção. Isto foi feito através de um programa experimental que incluiu ensaios de caracterização física-química do solo e do licor, ensaios edométricos, em edômetros especiais, para avaliar as características de colapso e de transporte de solutos, e ensaios de sucção pelo método do papel filtro. Os resultados do programa experimental mostraram que o solo é colapsível em presença de água, sendo sua colapsividade aumentada em presença do licor cáustico. Também indicaram que os parâmetros de transporte e sucção são fortemente afetados pela percolação do licor. A mudança destes parâmetros é função da concentração do licor.
In this work, characteristics of collapse of a laterítico soil submitted to percolation of a caustic liqueur to different concentrations are analysed. The soil comprises a quartzitic sand with a small fraction of kaolinitic clay. The liqueur is a caustic fluid, from an aluminium industry. In the present study, effects of the caustic liqueur infiltration were observed considering three aspects: collapse, solute transport and soil suction characteristics. This was done through an experimental program that included physical and chemical characterization of the soil and liqueur, special oedometer tests to evaluate simultaneously collapse characteristics and solute transport, and suction tests using the filter paper method. The results of the experimental program showed that the soil suffers volume change in presence of water, and its colapsivity is increased in presence of the caustic liqueur. They also indicated that the transport and suction parameters are affected strongly by the percolation of the liqueur.

Prediction as a tool in engineering has been used in taking right judgement in many of the professional activities. This being the fact, the role and significance of prediction in geotechnical practice needs no emphasis. Bulk of all man made structures are either made of soil or are resting on natural soil, involving large quantities of soil. Thus, it is often necessary for the geotechnical engineer to quickly characterize the soil and determine their engineering properties, so as to assess the suitability of the soil for any specific purpose. Obtaining these properties requires undisturbed samples, which involves time and money, and also elaborate laboratory procedures. Thus, it is desirable to find simpler and quicker methods of testing, using the data of which the engineering properties can be predicted satisfactorily especially so, for preliminary design purposes. Most often this can be achieved from simple tests known as inferential tests, and the engineering properties namely, compressibility, swell/collapse, hydraulic conductivity, strength and compaction characteristics can be obtained from empirical/semi-empirical correlations. The index tests namely the Atterberg limits form the most important inferential soil tests with very wide universal acceptance. These tests are relatively simple to perform and have provided a basis for explaining most engineering properties of soils in geotechnical practice. In this direction, this investigation has been carried out to correlate the engineering properties with the simple index properties and their indices, namely, the liquid limit, plastic limit, shrinkage limit, plasticity index and shrinkage index (liquid limit - shrinkage limit). Any good correlation in the prediction of engineering properties with the index properties will enhance the use of simple test for prediction purposes. This thesis is an attempt towards this direction. It is often necessary to identify the basic mechanisms controlling the engineering properties from a micro-mechanistic point of view and correlate with the index properties, thereby facilitating prediction of engineering properties better. Though attempts have been made in the past to predict the engineering properties of soils from the index properties/indic­es, they are not quite satisfactory. This thesis is an attempt to predict the engineering properties of fine-grained soils from the index properties taking into consideration the mechanisms controlling them. Since, the index properties are used for prediction of engineering properties, the existing methods of determining the same have been examined carefully and critically. It's satisfactory determination is found important because other indices namely plasticity index, Ip and shrinkage index, Is = (wL - ws), are determined based on it. Also the liquid limit is one of the important and widely used parameter in various existing correlations. In this direction, two new methods of determining the liquid limit have been developed, namely (i) absorption water content and liquid limit of soils and (ii) liquid limit from equilibrium water content under Ko-stress. In the absorption water content method, the water absorbed by an oven dried soil pat at equilibrium gives a good correlation with the liquid limit of soils. Here, the water holding capacity at equilibrium goes well with the mechanism of liquid limit, which is also the water holding capacity of a soil at a particular small but measurable shear strength. A good relationship is found to exit between the absorption water content, wA and the liquid limit, wL, and it is given as : WA = 0.92 wL (i) In the second method, namely, the liquid limit from equilibrium water content under K0-stress, which is the equilibrium water content under a Ko stress of 0.9 kPa is found to be equal to the liquid limit obtained from the cone penetration method of determining the liquid limit It is found that this method of determining the liquid limit overcomes the limitations of the conventional methods of determining the liquid limit, also easy to determine with a simple apparatus and has good repeatability. Determination of plastic limit of the soils by the rolling thread method often poses a problem especially when the soil is less plastic. Hence, to overcome this problem, a new method has been proposed to predict the plasticity index in terms of the flow index. The relationship between the plasticity index and the flow index by the cone penetration cup method is found to be better than by the percussion cup method. Since, the cone penetration method of the liquid limit determination is more popular than the percussion cup method, the flow index from the cone method is recommended to determine the plasticity index from the correlation as given below: (/p)c = 0.74 Ifc (ii) Thus, the plastic limit can be determined with the plasticity index, thereby dispensing with the determination of plastic limit by the thread method. The determination of consolidation characteristics form an important aspect in the design of foundations and other earth retaining structures. The determination of consolidation characteristics namely the compression index, the coefficient of consolidation and the coefficient of secondary compression is time consuming. So, researchers have resorted to correlating the compressibility behaviour with simple index properties. While attempts have been made in the past to correlate the compressibility behaviour with various index properties individually, all the important properties affecting the compressibility behaviour has not been considered together in any single study to examine which of the index property/properties of the soils correlates better with the compressibility behaviour, especially with the same set of test results. Number of existing correlations with the liquid limit alone as a primary index property correlating with the compression index have limitations in that they do not consider the plasticity characteristics of the soils fully. The index parameter, shrinkage index, Is has a better correlation with the compression index, Cc and also the coefficient of volume change, mv than plasticity index. Coefficient of consolidation, Cv has also shown to correlate well with shrinkage index than the plasticity index. Even the coefficient of secondary compression, Cαε has shown to have a better correlation with shrinkage index than the plasticity index. However, liquid limit has a poor correlation with all the compressibility characteristics. The correlation of Cc and Cv with shrinkage index, Is is as given below: Cc = 0.007 (Is + 18) (iii) Cv = 3x10-2 (Is)-3.54 (in m2/sec) Further, to reduce the testing time of conventional consolidation test in order to obtain the compressibility characteristics, a new method known as rapid method of consolidation has been proposed, which is very effective in enormously reducing the time of consolidation without sacrificing the accuracy of the end results. The time required in the rapid method of consolidation testing could be as low as 4 to 5 hours to complete the whole test as compared to 1 to 2 weeks as the case may be by the conventional consolidation test. Using any curve fitting procedure the degree of consolidation, U for any pressure increment can be found out. Thus, the effective pressure at that stage can be calculated and further the pressure incremented without further delay. This procedure is repeated for every pressure increment with a load increment ratio of unity till the desired pressure level is reached. Even for a highly compressible soil like BC soil with a liquid limit of 73.5 %, the consolidation test could be completed within 5 hours by the rapid method, without any sacrifice of the accuracy of the results as compared to 7 days by the conventional method to reach a pressure of 800 kPa. Hydraulic conductivity is one of the basic engineering properties of soils. Of late hydraulic conductivity of fine-grained soils has assumed greater importance in waste disposal facilities. From the present investigation it is found that hydraulic conductivity with water for each pair of soils having nearly the same liquid limit but different plasticity properties is found to be vastly different, but found to correlate well with shrinkage index. A method to predict the hydraulic conductivity of fine -grained soils as a function of void ratio is proposed with the use of shrinkage index as given below: k = C [ ] (in m/sec) (v) 1 + e C = 2.5 x 10-4 (/s)-5.89 and n = 4 (vi) It has also been brought out that as the dielectric constant of the pore fluid decreases; there is a drastic increase in the intrinsic permeability of soil. These changes are attributed to the significant reduction in the thickness of diffuse double layer, which in turn is mainly dependent on the dielectric constant of the pore fluid. The quantification of the change in the hydraulic conductivity with the change in the pore fluids of extreme dielectric constant, i.e., from water to carbon tetrachloride could be expressed in terms of the volume of water held in the diffuse double layer and the same has a good correlation with shrinkage index. With the advancement in the knowledge of the engineering behaviour of fine-grained soils, there is an increasing trend toward larger involvement of fine-grained soils in earth structures and foundations. Though extensive work has been done in the past to understand the swelling behaviour of expansive soils and the mechanisms involved therein, it is yet not satisfactory. From the literature it can be seen that lot of work has been done to correlate the swell potential with various physical properties. The simple means of identifying the swelling type of soils is by means of free swell tests with the ratio of free swell with carbon tetrachloride to the free swell of water. The same has found to correlate well with the percent swell/collapse of the ten soils used in the present investigation. However, it was found that shrinkage index has a better correlation with the swell/collapse behaviour of fine-grained soils, compared to the liquid limit or the plasticity index. In this study, it is also shown that neither the liquid limit nor the plasticity index can qualitatively describe the swell/collapse behaviour of fine-grained soils. This has been attributed primarily to two different mechanisms governing montmorillonitic and kaolinitic soils separately. Even swelling pressure has shown to have a good correlation with shrinkage index. It is found that the compression index of the samples consolidated from the swollen condition correlates well with the shrinkage index. Laboratory determination of the compaction characteristics are very much important for use in earth work constructions. It is found that only the plastic limit bears a good correlation with the compaction characteristics namely optimum moisture content and maximum dry unit weight. This conclusion is also supported by the data from the literature. The correlations are given as: OMC = 0.92 wp (in percent) (viii) and ydmax = 0.23 (93.3 - wp) (inkN/m3) (ix) Liquid limit, plasticity index and shrinkage index do not bear any correlation with the compaction characteristics. It is quite possible that, the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, possibly the good correlation. A simple method to predict the compaction curve is proposed based on the plastic limit of the soils. Of all the important engineering properties, both volume change (compressibility and swelling) and hydraulic conductivity have good correlation with the shrinkage index. However, the compaction characteristics correlate well with the plastic limit. Herein, an hypothesis is proposed to possibly explain why shrinkage index has shown to be a better parameter to correlate with most of the engineering properties with the exception of the compaction characteristics. The liquid limit is a parameter which takes part of the plasticity characteristics of a soil. Recently it has been well brought out that shrinkage limit is primarily a function of how the varying grain sizes are distributed in a soil. Thus, shrinkage limit takes care of the gradation of the soil fractions in it. Thus, by considering the shrinkage index, which is the difference of the liquid limit water content on one end and shrinkage limit water content on the other end, the primary physical properties of the soils namely the plasticity and the grain size distribution are considered. This possibly explains the good correlation of shrinkage index with the engineering properties of fine-grained soils. However, compaction being a moulding of the soils into a compact state, it has a good correlation with the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, the good correlation. As the present investigation gives the correlative equations to predict the engineering properties of fine-grained soils from the appropriate index properties, which are obtained from simple and quick laboratory tests, it is hoped that this will go a long way in being a handy tool for a practicing geotechnical engineer in the preliminary assessment of fine-grained soils and thereby take appropriate judgement in various aspects of geotechnical constructions with it.

The ancient Maya of the Classic period (1700-1050 B.P.) relied on maize agriculture to support their populations. The agricultural systems they employed to produce that maize varied in form and degree of intensity, with more productive forms of agriculture needed in the Late Classic period (1350-1050 B.P.) to sustain the peaking population. It is likely that the ancient systems of production agriculture contributed to environmental degradation that in turn contributed to the pressures that culminated in the collapse of the civilization. In this study, stable carbon isotope ratios contained in the soil organic matter were used to further investigate ancient maize cultivation in the Petexbatan region of Guatemala. Maize, a plant that uses the C4 photosynthetic pathway, leaves a different carbon (13C) isotopic signal in the soil than the C3 plants of the native forest vegetation. Soil profiles were collected from various landscape features around the Classic Maya site of Aguateca: bajos (or wetlands), control locations (areas not conducive to agriculture), defensible locations (areas within or near defensive walls), rehoyadas (natural karst depressions), and upland locations (level soils from across the rest of the landscape). The samples were tested for various chemical and physical properties, and the bulk soil organic matter and humin fractions were analyzed on a mass spectrometer to determine δ13C values. Graphs of the isotopic values were examined and the bulk and humin δ13C enrichment values for the landscape feature categories were compared statistically using ANOVA methods. We determined that the bulk and humin δ13C values of the Bajo and Rehoyada categories showed significantly greater enrichment than the Control, Defensible, and Upland locations. This enrichment was likely the result of sustained periods of maize cultivation, especially in the Rehoyadas. Surface soil bulk and humin δ13C enrichment values do not show that the Bajo or Rehoyada categories are influenced by modern C4 vegetation, nor do the enrichment values of the Control, Defensible or Upland soils. In other words, C3 vegetation dominates each of the landscape features today under natural conditions and probably would have done so anciently absent human interference. (Savanna soils are an exception, but none were identified in the study area.) When the thinner midslope (Backslope) Rehoyada profiles were compared to Control, Defensive, and Upland samples of similar depth, the Backslope Rehoyada profiles had significantly greater bulk δ13C enrichment values that may have resulted from maize cultivation. There was also a significant difference among the surface soil bulk and humin δ13C values of the Backslope Rehoyada, Control, Defensive, and Upland categories, though the reasons are less clear. Both the Bajos and Rehoyadas would have been valuable agricultural resources for maize production for the ancient Maya.

During a survey of black cotton soil zones of Karnataka, indigenously stabilized black cotton soil deposits were encountered in Belgaum, Bijapur, Bagalkot and Gadag Districts of Karnataka. These modified black cotton soils have low swelling and negligible shrinkage tendencies. Owing to their low volume change potential on moisture content changes, these soils are widely preferred in earth construction activities. The exact origin of these modified black cotton soil deposits is not known. According to anecdotal references, these soils were prepared by mixing unknown proportions of wood ash, organic matter and black cotton soil and allowing them to age for unknown periods of time. As wood-ash was apparently used in their preparation, these modified black cotton soils are referred to as ash-modified soils (AMS) in the thesis. The practice of preparing ash-modified soils is no longer pursued in black cotton soil regions of Karnataka and the available supply of this indigenously stabilized soil is being fast depleted. Also, attempts have not been made to characterize the physico-chemical and engineering properties of AMS deposits of Karnataka. Given the widespread utilization of ash-modified soils in black cotton soil areas of Karnataka, there is a need to understand their physico-chemical and engineering behaviour and the physico-chemical mechanisms responsible for their chemical modification. Swelling and shrinkage of expansive soil deposits are cyclic in nature due to periodic climatic changes. Chemically stabilized black cotton soil deposits are also expected to experience cyclic wetting and drying due to seasonal climatic changes. The impact of cyclic wetting and drying on the swelling behaviour of natural expansive soils is well-documented. However, the impact of alternate wetting and drying on the swelling behaviour of admixture stabilized expansive soils (these include natural - ash-modified soils and laboratory - lime stabilized black cotton soils) has not been examined. Such a study would be helpful to assess the long term behaviour of admixture stabilized soils in field situations. To achieve the above objectives, experiments are performed that study: 1.The physico-chemical and engineering properties of ash-modified soils from different Districts of Karnataka. The physico-chemical and engineering properties of natural black cotton soil (BCS) specimens from locations adjacent to ash-modified soil deposits are also examined to understand and evaluate the changes in the engineering characteristics of the ash-modified soils due to addition of admixtures. 2. Identify the physico-chemical mechanisms responsible for the chemical stabilizationof ash-modified soils. 3.The influence of cyclic wetting and drying on the wetting induced volume changebehaviour of admixture stabilized black cotton soils, namely, ash-modified blackcotton soils and lime stabilized black cotton soils.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A compactação dos solos é uma atividade fundamental nas obras geotécnicas e sua correta execução é capaz de promover melhorias significativas no comportamento do solo. Desse modo, o conhecimento acerca do solo e o controle dos métodos de execução são indispensáveis para o bom desempenho de uma obra. A variação da umidade do solo e, consequentemente, da sucção em campo influencia diretamente no seu comportamento quando submetido ou não a sobrecargas. O controle da compactação em campo representa a alternativa mais viável para melhoria de solos colapsíveis. Solos de aterros mal compactados podem apresentar comportamento colapsível quando inundados. Nesse contexto, esta pesquisa trata de um estudo acerca da compactação como método de melhoria de um solo colapsível arenoso proveniente da região de Bauru-SP. Ensaios de caracterização, de compactação Proctor Normal, assim como ensaios edométricos convencionais e com controle de sucção compõem o programa experimental dessa pesquisa. A partir dos resultados obtidos, constatou-se que as deformações por colapso aumentam com a redução do grau de compactação do solo. A umidade inicial do solo antes da inundação também influencia a magnitude do colapso. Solos com baixas umidades iniciais apresentam maior colapso ao serem umedecidos. Para o solo estudado, deformações por colapso são pequenas e praticamente desprezíveis para solos compactados com grau de compactação mínimo de 90%. Ensaios realizados com amostras compactadas nas mesmas condições de compacidade do solo natural no campo demonstraram que a deformabilidade do solo é afetada por sua baixa densidade e que a magnitude dos colapsos podem ser superiores àquelas obtidas para o mesmo solo em condição natural. No trabalho, uma representação mais prática da relação dos potenciais de colapso com a curva de compactação do solo é proposta. Assim, verificou-se que a compactação deve ser realizada com um controle suficientemente capaz de reduzir os problemas advindos da colapsibilidade dos solos.
Soil compaction is an essential activity in geotechnical works and its proper execution is able to promote significant improvements in soil behavior. Thus, the knowledge of the soil and the control of implementation methods are indispensable for the good performance in work. Variation of soil moisture and, consequently, in soil suction field directly influences their behavior when submitted or not to overloads. The compaction field control is the most viable alternative for improving collapsible soils. Poorly compacted landfill soils can have collapsible behavior when flooded. In this sense, this research is a study of compaction as improvement method for a sandy collapsible soil from the region of Bauru-SP. Characterization tests, Proctor Normal compaction, as well as conventional oedometric tests and controlled suction oedometric tests are part of the research experimental program. From the results obtained, it was found that the collapse settlements increase with lower degree of compaction. The initial soil moisture before the flood also influences the magnitude of soil collapse. Soils with low initial moisture content have greater collapse when they are wet. For the studied soil, collapse settlements are small and almost negligible for soil with degree of compacted of 90%. Tests performed on samples compacted under the same conditions of natural soil compactness demonstrated that the soil deformability is affected by its low density and the collapse can be higher than the ones obtained in the same soil in natural condition. At this work, a more practical representation of the relationship of collapse potential with soil compaction curve is proposed. Thus, it was found that compaction can sufficiently reduce the problems arising from soil collapsibility with some control in process.

Suction caissons are a foundation system for offshore structures which offer a number of advantages over traditional piled foundations. In particular, due to the method of installation used, they are well suited for deep-water applications. The suction caisson consists of an open ended cylindrical shell, which is installed below the seabed in a sequence which consists of two loading phases. The caisson is first installed part way under self weight, with the installation being completed by lowering the pressure within the cylinder and thus allowing the ambient water pressure to force the caisson into the ground. This thesis examines a number of structural issues which result from the form of the caisson — essentially a thin walled cylinder — and the interaction of the caisson with the surrounding soil during installation. To do this, variational analysis and nonlinear finite element analysis are employed to examine the buckling and collapse behaviour of these cylinders. In particular, two issues are considered; the influence of the open end, and the interaction between the cylinder and soil on the buckling and collapse loads. First, the behaviour of open ended cylinders is considered, where the boundary condition at the open end is allowed to vary continuously from completely free to pinned, by the use of a variable lateral spring. This lateral spring restraint may be considered to represent the intermediate restraint provided by a ring stiffener which is not fully effective. The effect of various combinations of boundary conditions is accounted for by the use of a multiplier on the lower bound to the buckling load of a cylinder with classical supports. The variable spring at the open end may also be considered to be an initial, simple representation of the effect of soil restraint on the buckling load. More complex representations of the soil restraint are also considered. A nondimensional factor is proposed to account for the influence of this spring on the buckling load. One combination of boundary conditions, where the upper end of the caisson is pinned, and the lower end free (referred to as a PF boundary condition), is found to have buckling and collapse behaviour which is unusual for cylindrical shells. Buckling loads for such shells are much lower than would be found for cylinders with more typical boundary conditions, and of similar dimensions. More unusually however, PF cylinders are shown to have positive postbuckling strength. The behaviour is found to be a result of the large flexibility which results from the low restraint provided by the PF boundary conditions. This is shown by continuously decreasing the flexibility of the cylinder, by increasing the axial restraint at the pinned end. It is shown that this results in a large increase in buckling load, and a return to more usual levels of imperfection sensitivity. In particular, with an intermediate level of axial restraint, buckling loads and imperfection sensitivity are intermediate between those of PF shells with no, and with full, axial restraint. Overall however, collapse loads for PF cylinders with no additional restraint are well below those of cylinders with stiffer boundary conditions, for equal geometries. Eigenvalue buckling of cylinders fully and partially embedded in an elastic material are examined, and two analytical solutions are proposed. One of these is an extension of a method previously proposed by Seide (1962), for core filled cylinders, to pin ended cylinders which have support from both a core and a surrounding material. The second method represents the elastic support as a two parameter foundation. While more approximate than the first method, this method allows for the examination of a wider range of boundary conditions, and of partial embedment. It is found that the buckling load of the shell/soil system decreases as the embedment ratio decreases. Collapse of fully and partially embedded cylinders is also examined, using nonlinear finite element analysis. The influence of plasticity in the soil is also considered. For cylinders with small imperfections, it is found that the collapse load shows a large increase over that of the same cylinder with no soil support. However, as the size of initial geometric imperfections increases, it is found that the collapse load rapidly approaches that of the unsupported cylinder. In particular, in weak soils the gain in strength over the unsupported shell may be minimal. The exception to this is again PF cylinders. As these have relatively low collapse loads, even very weak soils are able to offer an increase in collapse load over the unsupported case. Finally, a summary of these results is provided in the form of guidance for design of such structures.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O comportamento dos solos não saturados é um tema amplamente estudado, tanto por meio de ensaios de laboratório quanto de campo. Fenômenos como o colapso dos solos são relativamente bem explicados pelos modelos elastoplásticos existentes, dos quais o Modelo Básico de Barcelona é um dos mais utilizados e difundidos no meio acadêmico. Apesar dos avanços obtidos, ainda existe certa escassez de estudos que comparem o comportamento previsto por tais modelos a resultados de situações reais de engenharia. Esta pesquisa teve como objetivo simular numericamente resultados de recalques devidos a carregamentos e inundação de provas de carga em placa e de protótipos de sapata construídas sobre solo natural e compactado em cava. Com os resultados buscou-se analisar a eficiência da técnica de compactação para mitigar o problema do colapso do solo. Para isso, ensaios de compressão triaxial e edométricos com sucção controlada, bem como ensaios de curva de retenção e condutividade hidráulica foram realizados para determinação dos parâmetros constitutivos hidráulicos e mecânicos do solo natural e compactado que foram utilizados no programa Code_Bright para simulação numérica dos resultados de campo. Os resultados demonstraram a capacidade do modelo em reproduzir o comportamento do solo no campo. Demonstraram também que o uso da compactação do solo que preconiza compactar em cava uma camada de espessura equivalente à largura da sapata é viável para redução da colapsibilidade, mas depende do nível das tensões atuantes nas fundações e da tolerância aos recalques. Tensões propagadas para a camada de solo natural superiores à tensão de pré-adensamento do solo natural saturado provocarão recalques por colapso quando o solo for umedecido.
The behaviour of unsaturated soils is a widely studied theme around the world, both by utilising laboratory and field tests. Phenomena like soil collapsibility are relatively well explained by the existing elastoplastic models, among which the Barcelona Basic Model is the most widely used in the academic field. Despite the recent advances, there is still a scarcity of papers that compare the behaviour predicted by constitutive models and results of real engineering problems. This research aims to numerically simulate the results of settlement due to loading and wetting of load tests built both on undisturbed and compacted soil. The results were analysed in order to study the efficacy of the soil compaction technique in mitigating soil collapse. Suction controlled triaxial compression and oedometer tests, as well as soil water retention curve and hydraulic conductivity experiments were conducted to determine the hydraulic and mechanic parameters used in the software Code_Bright to numerically simulate field results. The results highlight the capability of the model in reproducing the analysed field behaviour. They also show that the technique that involves compaction of the soil equal to the footing’s width is viable to reduce its collapsibility, but its efficacy will also depend on the tensions applied on the foundation and on the tolerable settlement values. Tensions that are propagated to the natural soil layer that are higher than its preconsolidation stress will cause collapse settlements and wetted.

Orientador: José Augusto de Lollo
Banca: Leandro Eugenio Silva da Cerri
Banca: Wilson Manzoli Júnior
Resumo: O colapso de solos é um fenômeno típico de solos altamente porosos quando saturados, induzindo recalques significativos em fundações de obras civis, comprometendo total ou parcialmente estas obras. Tal fenômeno é bastante comum nos solos arenosos que ocorrem em boa parcela do Estado de São Paulo e em particular na cidade de Ilha Solteira. A grande disseminação de processos de colapso de solos em todo o Estado faz com que seu estudo seja imprescindível para o entendimento das variáveis que os condicionam e dos fatores que os desencadeiam. A proposta deste trabalho foi caracterizar o processo de colapso de solos na área urbana de Ilha Solteira, em termos de sua ocorrência, condicionantes, mecanismos e conseqüências, com o objetivo de avaliar e representar cartograficamente o risco de ocorrência deste processo. Os estudos mostraram que na área estudada a associação do comportamento natural do solo com problemas em obras de infra-estrutura urbana (redes de água e esgoto) induz uma situação de alta suscetibilidade de ocorrência de colapso de solos, o que pode ser notado pela disseminação de ocorrências por toda a área. A avaliação do risco de colapso de solos permitiu classificá-lo em alto, médio e baixo grau. As informações obtidas na avaliação de risco fundamentam a elaboração de medidas para eliminar ou reduzir os riscos instalados e ainda para evitar a instalação de novas áreas de risco. O resultado final foi a elaboração de uma carta de cadastramento de risco de colapso de solos e, a partir desta, a elaboração de uma carta de zoneamento de risco, constituindo-se em importantes ferramentas para projetos e obras de ocupação, além de fornecerem subsídios para elaboração de planos de seguro de edificações. A metodologia utilizada para avaliação e representação de risco de colapso de solos poderá ser aplicada em estudos nos bairros mais... (Resumo completo, clicar acesso eletrônico abaixo).
Abstract: Soil collapse is a characteristic process in porous soils when saturated and produce large settlements in civil engineering foundations. This process is very common in typical fine sand soils present in State of São Paulo large areas, thus Ilha Solteira region. Due this process has affected large areas of São Paulo State the study of soils with collapsible behavior is very important to understand variables that cause or are responsible for the process. This work proposed to characterize the process of soil collapse (events, causes, mechanisms, consequences) in the Ilha Solteira urban area, purposing to evaluate and to present the risk of soil collapse on a chart. Studies showed that in the Ilha Solteira city the association of natural behavior of soil with problems in urban infrastructure works (water and sewage pipes) characterize a situation of high susceptibility of soil collapse, which can be observed by dissemination of occurrences by total area. The evaluation of soil collapse risk permitted to classify it in high, medium and small degree. Information gained in this risk evaluation is important for take the necessary steps for reduce, eliminate or avoid the problem of soil collapse. The final result was the representation of the soil collapse risk on cadastre and zoning charts, which constitute on important tool for adopting construction guidelines, besides to provide subsidies for elaboration of edifications insurance. Respecting locals specifications, the methodology utilized for evaluation and representation of risk of soil collapse can be applied in studies in other areas with similar problems.
Mestre

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
O colapso de solos é um fenômeno típico de solos altamente porosos quando saturados, induzindo recalques significativos em fundações de obras civis, comprometendo total ou parcialmente estas obras. Tal fenômeno é bastante comum nos solos arenosos que ocorrem em boa parcela do Estado de São Paulo e em particular na cidade de Ilha Solteira. A grande disseminação de processos de colapso de solos em todo o Estado faz com que seu estudo seja imprescindível para o entendimento das variáveis que os condicionam e dos fatores que os desencadeiam. A proposta deste trabalho foi caracterizar o processo de colapso de solos na área urbana de Ilha Solteira, em termos de sua ocorrência, condicionantes, mecanismos e conseqüências, com o objetivo de avaliar e representar cartograficamente o risco de ocorrência deste processo. Os estudos mostraram que na área estudada a associação do comportamento natural do solo com problemas em obras de infra-estrutura urbana (redes de água e esgoto) induz uma situação de alta suscetibilidade de ocorrência de colapso de solos, o que pode ser notado pela disseminação de ocorrências por toda a área. A avaliação do risco de colapso de solos permitiu classificá-lo em alto, médio e baixo grau. As informações obtidas na avaliação de risco fundamentam a elaboração de medidas para eliminar ou reduzir os riscos instalados e ainda para evitar a instalação de novas áreas de risco. O resultado final foi a elaboração de uma carta de cadastramento de risco de colapso de solos e, a partir desta, a elaboração de uma carta de zoneamento de risco, constituindo-se em importantes ferramentas para projetos e obras de ocupação, além de fornecerem subsídios para elaboração de planos de seguro de edificações. A metodologia utilizada para avaliação e representação de risco de colapso de solos poderá ser aplicada em estudos nos bairros mais... .
Soil collapse is a characteristic process in porous soils when saturated and produce large settlements in civil engineering foundations. This process is very common in typical fine sand soils present in State of São Paulo large areas, thus Ilha Solteira region. Due this process has affected large areas of São Paulo State the study of soils with collapsible behavior is very important to understand variables that cause or are responsible for the process. This work proposed to characterize the process of soil collapse (events, causes, mechanisms, consequences) in the Ilha Solteira urban area, purposing to evaluate and to present the risk of soil collapse on a chart. Studies showed that in the Ilha Solteira city the association of natural behavior of soil with problems in urban infrastructure works (water and sewage pipes) characterize a situation of high susceptibility of soil collapse, which can be observed by dissemination of occurrences by total area. The evaluation of soil collapse risk permitted to classify it in high, medium and small degree. Information gained in this risk evaluation is important for take the necessary steps for reduce, eliminate or avoid the problem of soil collapse. The final result was the representation of the soil collapse risk on cadastre and zoning charts, which constitute on important tool for adopting construction guidelines, besides to provide subsidies for elaboration of edifications insurance. Respecting locals specifications, the methodology utilized for evaluation and representation of risk of soil collapse can be applied in studies in other areas with similar problems.

Esta tese apresenta um estudo de solos colapsíveis utilizando provas de carga em placas executados com inundação da cava. Durante o ensaio a sucção foi monitorada com tensiômetros instalados em cinco profundidades distintas. A inundação da cava foi também monitorada pelo uso da técnica de reflectometria no domínio do tempo. Desta forma pode-se acompanhar a evolução da frente de infiltração e da sucção durante todas as fases do ensaio. Foi introduzido também o uso da tomografia computadorizada para registrar as alterações causadas no solo pelo carregamento e posterior inundação. O acompanhamento da frente de infiltração durante o ensaio foi importante para conhecer a profundidade de influência do colapso no maciço do solo. De posse dos valores de sucção, foi possível a utilização de modelos para solo não saturado para verificar a sua aplicabilidade na previsão de comportamento de estruturas de fundação. A tomografia computadorizada forneceu informações a respeito da distribuição de massa específica do solo antes e depois do carregamento, permitindo concluir que a região mais afetada pelo colapso se restringe a 0,25 D.
This thesis presents a soil collapse study using plate load tests performed with soaking the test pit. During the test suction was monitored by tensiometers embedded at five different depths. Thus, it was possible to follow the wetting front and suction evolution all over the tests stages. lt was also introduced the computerized tomography technique to record the soil changing caused by loading and wetting. Monitoring the wetting front during the test was important to know the influence depth of collapse at soil mass. Having the suction values it was possible to use behaviour models of unsaturated soils to verity their applicability on predicting foundations structure settlements. The computerized tomography yields informations about soil unit weight distribution before and after loading, allowing concludes that collapse most affected region is restrained up to 0.25 D.

A maior parte dos acidentes em edifícios, causados por falhas de projeto ou de execução, ocorre na fase de construção. Além de causar prejuízos financeiros, eles colocam em risco a vida dos trabalhadores da obra. Porém, mais graves são os acidentes verificados após o término da construção. Além dos prejuízos serem muito maiores, eles podem envolver pessoas de todos os tipos, crianças, mulheres e idosos. São muitos os casos em que o colapso global do edifício decorre de problemas na fundação. Esse é o caso do edifício considerado neste trabalho, localizado no litoral norte do Estado de São Paulo. Trata-se de um edifício para veraneio, em alvenaria estrutural, com garagem no térreo e quatro andares de apartamentos, apoiado em estacas pré-moldadas, cravadas em solo instável. Pouco tempo após a conclusão e parcialmente ocupado, apresentou recalques e patologias significativas que exigiram providências, reforço de pilares de alvenaria inclusive. Antes que fossem detectadas as causas dos recalques, durante uma madrugada, o edifício desabou: em um lado do edifício, o primeiro pavimento encostou-se ao chão. Felizmente, era um dia-de-semana, fora da alta temporada, e não havia pessoas no seu interior. Também o vigia estava fora do edifício e nada sofreu, além de um grande susto. Os objetivos deste trabalho são descrever o problema ocorrido com esse edifício e analisar as causas e as providências possíveis para sua recuperação, já que os andares superiores praticamente nada sofreram. Serão apresentados os resultados de uma investigação no local e de uma análise para determinação dos esforços e das causas da ruptura das estacas, que provocaram o colapso do edifício. Ficou evidente que o aterro localizado sobre o pavimento térreo e o sistema de fundação do edifício não estavam adequados para o tipo de solo do terreno. Tais fatores tiveram papel fundamental para a ruptura do sistema. A importância de se conhecer minuciosamente essas causas transcende a presente obra, pois pelo mesmo motivo, outras construções podem apresentar danos semelhantes.
Most of the buildings accidents, caused by project flaws or of execution, it happens in the construction phase. Besides causing financial damages, they put in risk the workers life. However, more serious accidents are verified after the end of the construction. Besides the damages are larger, they can involve all types of people, children, women and senior. In many cases the global building collapse elapses of foundation problems. That is the case of the building considered in this work, located in the north coast of São Paulo State. Treated of a building for summer vacation, in structural masonry, with garage in the earthy pavement and four floors of apartments, leaning in premolded piles, nailed in unstable soil. After the conclusion and partially in use, it presented repress and significant pathologies that demanded providences, column masonry reinforcement besides. Before detected the repress causes, during one dawn, the building tumbled: on a side of the building, the first pavement was leaned to the ground. Happily, it was a weekday, out of the high season, and there were not people inside. Also the watchmen was out of the building and nothing suffered, besides a great fright. The objectives of this healthy work are to describe the problem happened with that building, to analyze the causes and the possible providences for it recovery, since the superior walks practically nothing suffered. The results of a local investigation, an analysis for determination the efforts and the causes of the piles rupture will be presented, that provoked the building collapse. It was evident that the located embankment on the earthy pavement and the building foundation system, they were not adapted for the soil type of the land. Such factors had fundamental paper for the system rupture. The importance of knowing those causes thoroughly, transcends to present work, because for the same reason other constructions can present similar damages.

Ce mémoire de thèse est consacré à l'étude expérimentale du comportement hydromécanique d'un lœss naturel non saturé effondrable provenant d'un site proche de la ville de Bapaume (nord de la France) dans une zone où des problèmes de tassement le long de la ligne nord du TGV ont été attribués à l'effondrement du lœss, du fait d'infiltrations d'eau. Un nouvel appareil triaxial permettant de mesurer localement l'ensemble des caractéristiques du loess non saturé (déformation, teneur en eau et succion) a été développé. La courbe de rétention d'eau, déterminée à l'aide d'un tensiomètre de haute capacité et de la méthode du papier filtre a fait l'objet d'une attention particulière : elle présente autour de la teneur naturelle une zone sans hystérésis bordée par deux boucles d'hystérésis des côtés secs et humides. L'analyse de la courbe de rétention et du phénomène d'hystérésis a été approfondie grâce à une étude microstructurale réalisée à l'aide de la porosimétrie au mercure et de la microscopie électronique à balayage. Une structure assez complexe composée d'un arrangement métastable de grains de limon secs (probablement liés par la recristallisation du calcaire) et d'une phase argileuse répartie de façon hétérogène a été mise en évidence. L'étude du comportement hydromécanique a compris une investigation de l'effondrement à partir de faibles valeurs de contraintes proches de la contrainte in-situ, à l'aide d'essais oedométriques à taux de déformation constant avec mesures de succion. Le maximum d'effondrement et une dépendance fonction de la vitesse de chargement ont été identifiés. Une campagne d'essais triaxiaux à différentes teneurs en eau constantes avec mesure de succion a permis de déterminer l'allure de la limite élastique du limon naturel dans un diagramme p/q, ainsi que ses variations avec la teneur en eau et la succion et confirmer l'écrouissage en succion

Des approches géologiques et morphologiques, ainsi que des modèles analogiques, ont été utilisés pour étudier pour la première fois le rôle de la tectonique active durant le développement structural des volcans de l'arc équatorien. En Equateur, la morphologie des volcans reflète un développement structural complexe, influencé par la superposition de différentes interactions volcano-tectoniques, autant dans le régime gravitationnel local que dans le régime tectonique régional. Ces interactions peuvent contrôler le développement de structures volcaniques majeures, tels que les effondrements de flanc, l'emplacement d'évents latéraux et la taille et la forme des édifices volcaniques. Un exemple de ces interactions est le volcan Imbabura (nord du pays), qui est composé de cinq unités stratigraphiques et structurales majeures. Au cours du développement de l'Imbabura, l'emplacement de ces unités a été fortement contrôlé et influencé par l'interaction de l'édifice volcanique avec : 1- la faille régional dextre 'El Angel-Rio Ambi' ; et 2- la pente de son substratum. Certaines structures observées dans les dépôts d'avalanche de débris volcaniques sont la conséquence des structures développées aux stades initiaux des effondrements de flanc

Esta tese apresenta um estudo de caso de colapso dos solos que ocorreu durante e após o enchimento do reservatório da UHE Três Irmãos. A construção desta barragem e o subseqüente enchimento do reservatório elevaram significativamente o lençol freático, causando colapso do solo em algumas áreas. Muitos trabalhos de campo e de laboratório foram realizados para determinar o potencial de risco associado às edificações existentes no local. A elevação do lençol freático foi monitorada especialmente para o estudo de recalques de edificações. Esta pesquisa trata do estudo deste caso histórico, recuperando informações existentes e executando ensaios adicionais com sucção controlada para caracterizar o comportamento não saturado do solo. O conjunto de dados obtidos foi usado para modelar recalques reais de edificações monitoradas, considerando o Modelo Básico de Barcelona, BBM, (Alonso et al., 1990) como o modelo constitutivo mecânico do solo e o programa de elementos finitos Code_Bright. A tese apresenta a definição dos parâmetros constitutivos do solo, a calibração dos modelos, análises de sensibilidade do modelo adotado, mostrando que os resultados modelados se ajustaram satisfatoriamente aos valores de recalques medidos no campo. A partir dos resultados obtidos numericamente, constatou-se que as deformações por colapso aumentam com a redução da sucção sem saturar o solo e que os maiores colapsos são observados quando o solo é gradualmente submergido. Como a profundidade de influência da carga de fundação é muito baixa comparada à espessura da camada colapsível, muitas das deformações por colapso são resultados do peso-próprio do solo, durante o equilíbrio sob as condições hidrodinâmicas transiente e final.
This thesis presents a case history of soil collapse that took place during and after reservoir filling of Três Irmãos dam in Brazil. The construction of this dam and subsequent reservoir filling has raised the local groundwater table up to 20 m, causing soil collapse that affected many buildings. Many field and laboratory tests were conducted to determine potential risk and damage of existing buildings. The groundwater rise was monitored in some points of the region and the most susceptible buildings were also monitored specially for settlements. This work deals with the study of this case history of soil collapse, recovering existing information and performing additional suction controlled soil tests to characterize the non saturated soil behavior. This set of data was used to model the collapse settlement, considering the Barcelona Basic Model, BBM, (Alonso et al. 1990) as the soil constitutive model and the Code_Bright finite element program and, finally numerical results were compared with field ones. The thesis addresses soil parameters definition from laboratory and field tests, model calibration, sensibility analysis of the adopted model and it shows that the modeled results nicely fitted the measured values of collapse settlements. Amongst the many qualitative and quantitative findings, it is shown that collapse deformation arises from suction variation without saturating the soil and that the largest collapse rate is observed when the soil is gradually submerged. As the depth of influence of foundation load is very low compared to collapsible layer thickness, much of collapse deformation is the result of soil self weight, during equilibrium under the transient and final hydrodynamics condition.

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Os solos não saturados são materiais multifásicos e de comportamento complexo que podem ser encontrados em depósitos de grande espessura onde são construídas as obras de engenharia civil. O entendimento do comportamento tensão-deformação/fluxo desses solos tem sido aprimorado com o desenvolvimento de experimentos e modelos constitutivos que são aplicados para a previsão de comportamentos e análises de desempenho das obras geotécnicas. Tais modelos têm sido utilizados para simular diversos resultados de ensaios de laboratório de solos não saturados compactados, porém, simulações de resultados de ensaios de campo em solos não saturados naturais ainda têm sido pouco exploradas. A proposta deste trabalho é simular numericamente o comportamento Hidro-Mecânico de um solo arenoso não saturado via método de elementos finitos em ensaios de prova de carga em placa. Os parâmetros constitutivos do solo são provenientes de resultados de ensaios de laboratório realizados com controle de sucção. O programa de elementos finitos Code_Bright foi utilizado para a simulação dos resultados dos ensaios das provas de carga em placa realizadas em campo. Os resultados obtidos numericamente demonstraram a capacidade do modelo constitutivo mecânico em reproduzir adequadamente os resultados dos ensaios. A partir dos resultados, constatou-se que os recalques são fortemente afetados pela variação da sucção, demonstrando o comportamento colapsível do solo diante de aplicação de tensões e mudanças de umidade e sucção. O parâmetro constitutivo mecânico po*, tensão de pré-adensamento isotrópica do solo saturado, influencia significativamente o comportamento do solo, assim como a magnitude do colapso por inundação. Os resultados demonstraram a importância da condição não saturada na previsão de comportamento e o quanto tal condição pode afetar o dimensionamento de fundações diretas em solo não saturado de comportamento colapsível. O trabalho oferece informações básicas no tocante à estimativa da tensão admissível considerando a variabilidade sazonal decorrente da sucção no solo.
Unsaturated soils are multiphase materials with complex behavior that can be found in large thickness deposits where civil engineering works are built. The understanding of the stress-strain/flow behavior of these soils has been improved with the development of experiments and constitutive models that are applied to behavior predictions and performance analysis of geotechnical works. Such models have been used to simulate several laboratory test results on compacted unsaturated soils, however, simulation of field test results on natural unsaturated soils have been little explored. This work aims to simulate numerically the Hydro-Mechanical behavior of an unsaturated sandy soil by finite element method in plate loading tests. Constitutive parameters of the soil come from the laboratory test results performed with controlled soil suction. The program Code_Bright was used to simulate plate loading test results. The results showed the capacity of the constitutive mechanical model to reproduce the test results. The settlements are strongly affected by the soil suction variation, demonstrating the collapsible behavior for stress, moisture content or soil suction changes. The constitutive mechanical parameter po*, preconsolidation stress for saturated condition, affected significantly the soil behavior, as well as the magnitude of the collapse by wetting. The results presented the great importance of the unsaturated status of the soil in prediction behavior and how this condition can affect the design of foundations in unsaturated soils with collapsible behavior. This study provides basic information concerning the estimation of admissible stress, taking the seasonal variability due to the soil suction.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico
Este trabalho compreende um estudo experimental e uma aplicaÃÃo numÃrica sobre os solos nÃo saturados colapsÃveis. Foram realizados ensaios em amostras de solo coletadas em uma jazida, localizada no municÃpio de QuixadÃ, no estado do CearÃ, onde foi construÃda uma pequena barragem com esse material. Foram realizados ensaios de caracterizaÃÃo cujo objetivo à identificar a amostra analisada. Em seguida, realizaram-se ensaios de compactaÃÃo com diferentes energias com o fim de verificar a variaÃÃo entre a massa especÃfica seca e a energia de compactaÃÃo para o solo utilizado no maciÃo da barragem. Posteriormente, ensaios de adensamentos duplo e simples foram executados em amostras com baixos valores de massa especÃfica seca e baixa umidade, visando estudar o fenÃmeno do colapso em solos presumivelmente compactados no ramo seco da curva de compactaÃÃo. Com os resultados dos ensaios realizou-se uma modelagem numÃrica de fluxo e equilÃbrio, com os programas Slide 6.0 e UNSTRUCT, utilizados de forma associada, para previsÃo do comportamento tensÃo x deformaÃÃo (colapso) da barragem experimental. A seÃÃo transversal da barragem à constituÃda no seu nÃcleo, com o material compactado na umidade Ãtima e com a energia de Proctor Normal e espaldares no ramo seco. O objetivo à verificar a eficiÃncia do maciÃo construÃdo com reduÃÃo de custos (diminuiÃÃo de terraplenagem) e reduÃÃo do consumo de Ãgua, que se torna uma soluÃÃo importante para construÃÃo de pequenas barragens no semiÃrido, seÃÃo essa proposta por Miranda (1988). Os estudos experimentais e numÃricos apontaram para uma obra com essas caracterÃsticas e em condiÃÃes de estabilidade.

This thesis analyzes the hydro-mechanical behavior under a generalized stress state of a compacted mixture of sand (30%) and clayey (70%) at a low density. The experimental study focuses on the analysis of shear strength at different stress paths and at different initial suction values (as-compacted), and the response to collapse due to saturation. For the investigation a conventional triaxial equipment and a hollow cylinder apparatus with automatic control of internal and external chamber pressures, back pressure and axial stress and torque were used. The equipment was not adapted for the measurement of deformations of unsaturated soils, being necessary a calibration of the volumes of the chambers and the relation with the change of volume of the sample. Preliminary tests were performed to better understand the studied of the mixture, like compaction tests, retention curve, oedometer compressibility tests and direct shear and obtain strength, suction and permeability parameters. The shear strength was analyzed through tests carried out in conventional triaxial equipment and in hollow cylinder apparatus, with different stress paths, changing the stress state, valued by parameter b (or Lode angle) and different compaction water content. Low deformation cyclic tests were performed to obtain the shear module in hollow cylinder, using two types of soil, the sand / clayey mixture and a MX-80 bentonite, seeking to analyze the possibilities of testing with the equipment and compare it to the results obtained in other. The results showed that the module obtained in other equipment is greater than those found in hollow cylinder, approaching with increasing deformations, behavior observed for both materials. The collapse tests were performed with constant mean stress (p= 200kPa), different values of deviator stress (q= 10, 75, 185kPa) and different intermediate stress values (b= 0, 0,5, 0,8). The results of the shear strength allowed to define the variation of the critical state line with the Lode angle and the matric suction. Different yield surface models were used for isotropic and anisotropic surface, to verify the rotation of the surface and observe the presence of anisotropic behavior. In all models the change in the critical state line due to the Lode angle was considered. The yield surfaces adjusted well to the experimental results, considering the inclination of the surface and the dependence of the Lode angle. It was observed that the size of the yield surface depends on the suction and the state of tension applied and, a relationship of the parameters was proposed, in order to normalize the yield surface. It was noted that the surface has an inclination due to static compaction, which can be obtained by compaction stresses. It was also observed that this inclination may change depending on the value of b applied to the stress path. Saturation tests under generalized load were analyzed using the BBM model (Barcelona Basic Model) and showed a greater dependence on the magnitude of the deviator stress applied than on the variation of parameter b, and presented a good relationship with the total deformation values. An empirical equation was proposed to estimate the potential for collapse for the different values of b in hollow cylinder, triaxial and oedometer tests.
Esta tesis analiza el comportamiento hidro-mecánico bajo un estado generalizado de tensiones de una mezcla de arena (30%) y arcilla (70%) compactada a una baja densidad. El estudio experimental se centra en el análisis de la resistencia al corte a diferentes trayectorias tensionales a diferentes valores de succión inicial (post compactación) y, a la respuesta al colapso debido la saturación. Para la investigación, se utilizó un equipo triaxial convencional y un equipo de cilindro hueco con control automático de las presiones de cámara interna y externa, de cola y de tensión axial y torque. El equipo no estaba adaptado para la medición de deformaciones de suelos no saturados, siendo necesario una calibración de los volúmenes de las cámaras y la relación con el cambio de volumen de la muestra. Se realizaron ensayos preliminares de compactación, curva de retención, ensayos de compresibilidad edométrica y corte directo, para conocer mejor la mezcla estudiada y obtener parámetros de resistencia, succión y permeabilidad. La resistencia al corte fue analizada a través de ensayos ejecutados en equipo triaxial convencional y en un equipo de cilindro hueco, con diferentes trayectorias tensionales y variando el estado de tensiones, valorado por el parámetro b (o ángulo de Lode) y a diferentes humedades de compactación. Se realizaron ensayos de deformación cíclica a baja deformación para la obtención del módulo de corte en cilindro hueco, utilizando dos tipos de suelo, la mezcla arena/arcilla y una bentonita MX-80, buscando analizar las diferentes posibilidades de ensayos con el equipo y compararlo a los resultados obtenidos en otros equipos. Los resultados mostraron que el módulo obtenido en otros equipos es mayor inicialmente que los encontrados en cilindro hueco, acercándose con el aumento de las deformaciones, comportamiento observado para ambos materiales. Los ensayos de saturación fueron realizados con tensión media constante (p=200kPa), diferentes valores de tensión desviadora (10, 75, 185kPa) y diferentes valores de b (0, 0.5, 0.8). Los resultados de los ensayos de resistencia al corte permitieron definir la variación de la línea de estado crítico con el ángulo de Lode y la succión matricial. Se utilizaron diferentes modelos para la superficie de fluencia, isótropa y anisótropa, para analizar el comportamiento del material y observar la presencia de un comportamiento anisótropo. En todos los modelos se consideró el cambio en la línea de estado crítico debido al ángulo de Lode. Las superficies de fluencia se ajustaron bien a los resultados experimentales, considerando la inclinación de la superficie y la dependencia del ángulo de Lode. Se observó que el tamaño de la superficie de fluencia depende de la succión y del estado de tensión aplicado y, se propuso una relación de los parámetros, a fin de normalizar las superficies de fluencia. Se notó que la superficie presenta una inclinación debido la compactación estática, la cual puede ser obtenida por las tensiones de compactación. También se observó que esta inclinación puede sufrir cambios dependiendo del valor de b aplicado a la trayectoria de tensión. Los ensayos de saturación bajo carga generalizada fueron analizados utilizando el modelo BBM (Barcelona Basic Model) y mostraron una dependencia mayor de la magnitud de la tensión desviadora aplicada que de la variación del parámetro b, y presentó buena relación con los valores totales de deformación. Se propuso una ecuación empírica para estimar el potencial de colapso para los diferentes valores de b en ensayos en cilindro hueco, triaxial y edómetro.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
A common problem of the Brazilian semiarid regions is water scarcity. An alternative to attenuate this severe regional problem consists in storing water during the rainy season, in dams with small storage volumes, usually built with inefficiently compacted embankments, which can contribute to the collapse during the first filling. The main goal of this work is to evaluate a construction methodology for earth dams in semiarid regions, taking into account the problems of inadequate compaction and water shortages. To achieve this, a study was done on a theoretical and experimental basis, in order to better understand the mechanical behavior of small dams that collapse during the first filling. An experimental dam was built in QuixadÃ-CE, following the proposition of Miranda (1988), which suggests a zoned cross section, built with low water content, with a better compacted core and side slopes with less efficient compaction. The embankment of this experimental dam was instrumented with piezometers (standpipes) and limnimetric rules, to monitor the filling and operation stages. Another developed study in this research refers to the avant-garde evaluation of suction in earth dams, using a device developed by researchers from the Department of Agricultural Engineering, at the Federal University of CearÃ, a capacitive sensor. To obtain the geotechnical parameters for the embankment soil, some laboratory tests were performed, such as characterization tests, compaction, consolidation and permeability tests, as well as shear strength and triaxial compression (saturated and unsaturated) ones, and also tests to determine the soil-water characteristic curve (using the filter paper method). The results were used in a numerical modeling of transient flow, using the software Slide, associated with UNSTRUCT, to predict the stress-strain behavior of the experimental dam. The results pointed to the occurrence of collapse in the soil structure of the slopes, which indeed happened after the first filling, since large longitudinal cracks were found in loco. The dam stability was also evaluated, by reducing the shear strength parameters, noting its stability, and thus proving efficient what Miranda (1988) proposed: a zoned embankment built with reduced costs of earthworks and low water consumption, contributing to the development of a low-cost methodology for the construction of small dams in the Brazilian semiarid.
Uma das problemÃticas do semiÃrido nordestino à a escassez de recursos hÃdricos. Para atenuar este forte problema regional, à comum realizar o armazenamento da Ãgua, durante o inverno, em barramentos com pequeno volume de acumulaÃÃo, construÃdos geralmente com maciÃos ineficientemente compactados, o que pode contribuir para a ruptura da obra durante o enchimento. O objetivo principal deste trabalho à avaliar uma metodologia de construÃÃo de barragens de terra em regiÃes semiÃridas, levando em consideraÃÃo os problemas de compactaÃÃo inadequada e escassez de Ãgua. Para tanto, foi empreendido um estudo, a partir de bases teÃricas e experimentais, a fim de melhor entender o comportamento mecÃnico de pequenas barragens que entram em colapso durante seu primeiro enchimento. Para tanto, foi construÃda uma barragem experimental no MunicÃpio de QuixadÃ-CE, seguindo a proposta de Miranda (1988), que sugere uma seÃÃo-tipo zoneada, construÃda com baixa umidade, tendo o nÃcleo melhor compactado e os espaldares executados com compactaÃÃo menos eficiente. O maciÃo desta barragem experimental foi, entÃo, instrumentado, com piezÃmetros e rÃguas linimÃtricas, para monitorar o enchimento e a operaÃÃo. Outro estudo desenvolvido nesta pesquisa foi o emprego vanguardista, na avaliaÃÃo da sucÃÃo em barragens de terra, de um equipamento desenvolvido por pesquisadores da Engenharia AgrÃcola da Universidade Federal do Cearà (UFC), para a determinaÃÃo da umidade do solo, um sensor capacitivo. Para a obtenÃÃo dos parÃmetros geotÃcnicos do maciÃo, foram realizados ensaios de caracterizaÃÃo, compactaÃÃo, adensamento duplo, permeabilidade e cisalhamento direto e de compressÃo triaxial (saturado e nÃo saturado), alÃm de ensaios para a determinaÃÃo da curva de retenÃÃo do solo (mÃtodo do papel de filtro). Os resultados foram utilizados em uma modelagem numÃrica de fluxo em regime transiente, com o auxÃlio do programa Slide, associados ao UNSTRUCT, para a previsÃo do comportamento tensÃo x deformaÃÃo do solo da barragem experimental. As anÃlises indicaram a ocorrÃncia de colapso da estrutura do solo dos taludes, fenÃmeno observado in loco apÃs o enchimento, jà que a obra apresentou grandes trincas longitudinais em seus taludes. A estabilidade da barragem tambÃm foi avaliada, atravÃs da reduÃÃo dos parÃmetros de resistÃncia ao cisalhamento, constatando sua estabilidade, e comprovando, assim, a eficiÃncia da proposta de Miranda (1988), de um maciÃo zoneado construÃdo com reduÃÃo de custos de terraplenagem e do consumo de Ãgua, contribuindo para o desenvolvimento de uma metodologia de baixo custo para a construÃÃo de pequenas barragens no semiÃrido brasileiro.

La présence d’une cavité naturelle ou anthropique dans un massif de sol représente une source importante de risque de désordre pour les infrastructures en surface et, dans les cas les plus graves, de perte en vies humaines. Dans le but de limiter ces risques, une solution préventive est privilégiée. Le renforcement des remblais par géosynthétique sur zones d’effondrement potentiel représente, aujourd’hui une solution très utilisée parce qu’elle est considérée plus pertinente techniquement et économiquement. En effet, les traitements traditionnels, comme le comblement des cavités ou leur pontage par dalles en béton armé, sont très coûteux et suppose une connaissance de la localisation de la cavité. Souvent utilisée pour des remblais granulaires, la solution de renforcement par géosynthétique est peu employée pour les remblais cohésifs de faible épaisseur. Plus précisément, les verrous scientifiques qu’il reste à lever sont liés à la méconnaissance des modes de rupture des remblais cohésifs sur cavité et à l’action des blocs effondrés sur la nappe. Pour répondre à ces interrogations, un consortium regroupant des chercheurs (3SR), des opérationnels (INERIS) et un producteur de géosynthétique (AFITEXINOV) s’est constitué dans le cadre du projet REGIC (Renforcement par Géosynthétique Intelligent sur Cavités naturelles ou anthropiques), financé par l’ADEME. L’un des objectifs du projet est de développer et de valider pour ce type d’application l’emploi d’un géosynthétique innovant à double raideurs et instrumenté par des fibres optiques.Cette thèse vise essentiellement à répondre à un des objectifs du projet : la compréhension des mécanismes d’effondrement du remblai renforcé par une nappe géosynthétique dans le contexte des remblais cohésifs. Il s’agit principalement d’un travail de modélisation numérique, effectué à l’aide du code de calcul SDEC qui couple éléments discrets et éléments finis. Il permet de simuler la phase d’ouverture de la cavité et la phase de chargement jusqu’à la rupture du remblai cohésif généralement de faible épaisseur. Le sol est modélisé par éléments discrets, la nappe par éléments finis. La modélisation en éléments discrets permet de bien reproduire numériquement le comportement du sol sous des grandes déformations, mais surtout de représenter la rupture par blocs de la couche de sol cohésif (géométrie des lignes de rupture, cinématique de rotation des blocs, etc.). La méthode des éléments finis a été retenue car plus apte à simuler la continuité de la nappe géosynthétique, son comportement en membrane et en traction (avec une évolution de la raideur avec le niveau de traction) et son interaction avec le sol. Ces travaux numériques ont été validés par des expérimentations sur modèle physique à échelle réduite et par des essais in situ, qui inclut notamment l’analyse de l’efficacité du géosynthétique innovant dont le comportement en traction est qualifié de « bimodule inversé ». La modélisation numérique a permis d’accéder à des variables ou à des grandeurs difficiles à mesurer en laboratoire et sur site : distribution des contraintes verticales transmise par le sol sur la nappe géosynthétique, analyse des reports de charge transmises sur les bords de la cavité, etc.Le modèle numérique développé dans le cadre de ce travail de thèse constitue un élément majeur pour l’analyse des phénomènes et mécanismes expérimentaux. En effet, la validation du modèle numérique a permis d’étendre de manière systématique son utilisation à différentes géométries, différentes formes de chargement en surface et différents matériaux de renforcement. Enfin, ce travail aboutit à quelques propositions pratiques pour le dimensionnement du géosynthétique par une méthode analytique dans le contexte des remblais cohésifs
The presence of a natural or anthropogenic cavity in a soil mass represents a major source of risk of disruption to surface infrastructures and, in the most serious cases, loss of human life. In order to limit these risks, a preventive solution is preferred. Reinforcement of embankments by geosynthetics in areas of potential collapse is nowadays a widely used solution because it is considered to be more technically and economically relevant. Indeed, traditional treatments, such as filling cavities or bridging them with reinforced concrete slabs, are very costly and require knowledge of the location of the cavity. Often used for granular backfill, the geosynthetic reinforcement solution is not so used for thin cohesive backfill. More precisely, the scientific obstacles that remain to be overcome are linked to the lack of knowledge of the failure modes of cohesive fillings in cavities and to the action of collapsed blocks on the water table. To answer these questions, a consortium of researchers (3SR), operational staff (INERIS) and a geosynthetics producer (AFITEXINOV) has been formed as part of the REGIC project (Reinforcement by Intelligent Geosynthetics on Natural or Anthropic Cavities), financed by ADEME. One of the objectives of the project is to develop and validate for this type of application the use of an innovative geosynthetic with double stiffnesses and instrumented with optical fibres.This thesis essentially aims to meet one of the project's objectives: the understanding of the collapse mechanisms of embankment reinforced by a geosynthetic sheet in the context of cohesive embankments. It is mainly a numerical modelling work, carried out using the SDEC calculation code that couples discrete elements and finite elements. It enables the simulation of the cavity opening phase and the loading phase up to the rupture of the cohesive fill, which is generally thin. The soil is modelled by discrete elements, the layer by finite elements. Discrete element modelling enables the behaviour of the soil under large deformations to be well reproduced numerically, but above all it enables the block failure of the cohesive soil layer to be represented (geometry of the failure lines, block rotation kinematics, etc.). The finite element method was chosen because it is better suited to simulate the continuity of the geosynthetic layer, its membrane and tensile behaviour (with an evolution of stiffness with the level of traction) and its interaction with the soil. This numerical work was validated by experiments on a reduced scale physical model and by in situ tests, which included in particular the analysis of the efficiency of the innovative geosynthetic whose tensile behaviour is qualified as "inverted bimodulus". Numerical modelling has provided access to variables or quantities that are difficult to measure in the laboratory and on site: distribution of vertical stresses transmitted by the ground to the geosynthetic sheet, analysis of load transfers transmitted to the edges of the cavity, etc.The numerical model developed within the framework of this thesis work constitutes a major element for the analysis of experimental phenomena and mechanisms. Indeed, the validation of the numerical model has made it possible to systematically extend its use to different geometries, different forms of surface loading and different reinforcement materials. Finally, this work leads to some practical proposals for the dimensioning of geosynthetics by an analytical method in the context of cohesive backfill

Phytophthora cinnamomi is an important pathogen of many plant species in natural ecosystems and horticulture industries around the world. In Western Australia, a high proportion of native plant species are susceptible to P. cinnamomi attack. Acacia pulchella, a resistant legume species native to Western Australia has been considered as a potential biological control tool against P. cinnamomi. To develop effective control methods, it is important to understand the interactions between the control agent and the different life forms of the pathogen. In this thesis the interactions are investigated between P. cinnamomi and varieties of A. pulchella which occur in jarrah (Eucalyptus marginata) forest and sand plain ecosystems. The soil inoculum of P. cinnamomi was compared under the potted plants of the three common varieties of A. pulchella, var. pulchella, var. glaberrima and var. goadbyi. These were grown in infected jarrah forest soil in the glasshouse and in vitro in a sterilised soil-less mix aseptically. Acacia urophylla (a species non suppressive towards P. cinnamomi) was also included as a control. An isolate of the most commonly found clonal lineage of P. cinnamomi in the jarrah forest, A2 type 1 was selected for use in experiments after testing showed it reliably produced zoospores and chlamydospores both axenically and in non-sterile conditions, in comparison to several other isolates. The lowest survival of P. cinnamomi inoculum was found under A. pulchella var. goadbyi plants grown both in non sterile soil and in aseptic soil-less mix. All the life forms of P. cinnamomi were affected by A. pulchella (Chapters 2, 3, 4 and 5). The soil leachates from potted plants of A. pulchella var. goadbyi reduced sporangial production (Chapter 2) and caused cytoplasm collapse of chlamydospores (Chapter 3). The confirmation was obtained that soil under A. pulchella was inhibitory to sporangial stage of P. cinnamomi and new evidence was obtained on chlamydospore inactivation. Cytoplasm collapse in the chlamydospores was observed both for chlamydospores on mycelial discs on Mira cloth exposed to the soil leachate and within infected roots buried in soils under the three varieties of A. pulchella plants. The effect was strongest under the plants of A. pulchella var. goadbyi and indicated that the chlamydospores of P. cinnamomi are unlikely to act as persistent structures under A. pulchella var. goadbyi plants. In Chapter 4, bioassays were conducted with axenically produced mycelia, chlamydospores and zoospores to test the inhibitory effect of the root exudates collected from aseptically grown A. pulchella var. goadbyi plants. The zoospores of the same isolate used in the soil leachate tests were immobilised (became sluggish and encysted) within one to two minutes. When incubated for 24 h, zoospores predominantly clumped and germ tubes were observed only from the clumped ones. Chlamydospores produced by four isolates of the common A2 type 1 strain and the only one A2 type 2 strain available at the time were tested. A higher percentage of chlamydospores collapsed and a very low percentage germinated after 24 h. Chlamydospores of all the A2 type 1 isolates were inhibited by the root exudates whilst the A2 type 2 isolate remained viable. The findings showed that the suppressive effect must be due at least in part to substances exuded by the A. pulchella plants. However, it appeared that the A2 type 1 isolates were more vulnerable to this effect than the single A2 type 2 isolate. In Chapter 5, the effect of season on sporangial suppression of P. cinnamomi was shown using field soils collected from three jarrah forest soil vegetation types and a Banksia woodland on Bassendean sand, collected in winter and summer. The effect of age of A. pulchella plants was demonstrated using the soils collected from rehabilitated bauxite mine pits. In all the locations soils were collected under A. pulchella plants and 5 m away from the nearest A. pulchella. An effect of soil type was evident as whilst the soil leachates made from the three lateritic jarrah forest soil types where A. pulchella is common in the understorey were suppressive to the sporangial stage of P. cinnamomi, this effect was not evident in the Bassendean sand under A. pulchella. A. pulchella soils collected in winter were less suppressive towards sporangial production than soils collected in summer. An effect of plant age was demonstrated as soil leachates from four year-old A. pulchella stands in rehabilitated bauxite mine sites were more suppressive for sporangia than leachates from one year-old stands. Further information on the behaviour of the pathogen in soil and in potting mix with and without A. pulchella was obtained by infecting lupin radicles with an isolate of each A2 type, 1 and 2 strains of P. cinnamomi and burying them in the soil under the three varieties of A. pulchella plants. After a week, the chlamydospores were mostly collapsed and hyphae deteriorated. Oospores were observed and in significant numbers under the potted plants of A. pulchella var. glaberrima. Isolates of all three clonal lineages of P. cinnamomi found in Australian soil were tested for the ability to produce oospores. Two isolates of the A1 and A2 type 2 and three isolates of the common A2 type 1 were screened. The two isozyme types of the A2 clonal lineage isolated in Australia varied in ability to self and produce oospores in planta in several soils from the jarrah forest. The isozyme type 2 of the A2 clonal lineage of P. cinnamomi produced oospores under these experimental conditions. This stimulation was not effective for most of the tested isolates of the A2 type 1 and the A1 clonal lineage. The in planta oospores were viable but dormant and the oogonial-antheridial associations were amphigynous both in vitro and in vivo. For the first time it was established that, the stimulus for selfing and oospore formation in the A2 type 2 of P. cinnamomi is available in some jarrah forest soils, with and without A. pulchella and also in the potting mix used. This raises important questions for the management of the pathogen. Several factors were identified as potential stimuli for selfing. Among them, soil nutrient levels and essentially enhanced sulphur presence were found important. Temperature also played a key role. Oospores were produced abundantly at 21 – 25 ºC but not over 28 ºC. The biology of P. cinnamomi has been studied for several decades but some important aspects remain un-researched. This thesis pioneers research into the in planta selfing aspect of the pathogen in soil. It also improved the understanding of the interactions between P. cinnamomi and A. pulchella which to some extent supports use of A. pulchella as a biological control tool against P. cinnamomi. However, attention is drawn to the natural mechanisms of this complex pathogen to survive in planta by producing oospores, the most persistent form of its life cycle.

Avalia-se o colapso de um solo residual, de comportamento laterítico, para líquidos inundantes de diferentes composições químicas, em profundidades de 1 até 4 metros, empregando-se provas de carga diretas e ensaios de adensamento. Explica-se o fenômeno do colapso, para cada líquido inundante, utilizando-se parâmetros obtidos em ensaios de caracterização, difração de raios X, microscopia eletrônica de varredura e ensaios químicos. A pesquisa é desenvolvida no Campo Experimental da UNESP de Bauru (SP), cujo solo local é uma areia fina argilosa, residual de arenito, enquadrada como Latossolo vermelho escuro a amarelo.
The collapse of a lateritic residual soil is evaluated, using liquid of different chemical compositions, in depths from 1 to 4 meters, and using plate load and oedometer tests. This work explains the phenomenon of the collapse, for each liquid, employing parameters obtained in characterization tests, X-ray diffraction, scanning electron microscope and chemical tests. The research is developed in the Experimental Field of the Civil Engineering Department of the São Paulo State University (UNESP), at Bauru (SP), where the local soil is residual derived from sandstone, and according to grain size classification it is a clayey fine sand. In the pedological classification it is a dark red to yellow Latosol.

Gypsum rich soils are found in many parts of the world, particularly in arid and semi-arid regions. Most gypsum occurs in the form of evaporites, which are minerals that precipitate out of water due to a high rate of evaporation and a high mineral concentration. Gypsum rich soils make good foundation material under dry conditions but pose major engineering hazards when exposed to water. Gypsum acts as a weak cementing material and has a moderate solubility of about 2.5 g/liter. The dissolution of gypsum causes the soils to undergo unpredictable collapse settlement leading to severe structural damages. The damages incur heavy financial losses every year. The objective of this research was to use geophysical methods such as free-free resonant column testing and electrical resistivity testing to characterize gypsum rich soils based on the shear wave velocity and electrical resistivity values. The geophysical testing methods could provide quick, non-intrusive and cost-effective methodologies to screen sites known to contain gypsum deposits. Reconstituted specimens of ground gypsum and quartz sand were prepared in the laboratory with varying amounts of gypsum and tested. Additionally geotechnical tests such as direct shear strength tests and consolidation tests were conducted to estimate the shear strength parameters (drained friction angle and cohesion) and the collapse potential of the soils. The effect of gypsum content on the geophysical and geotechnical parameters of soil was of particular interest. It was found that gypsum content had an influence on the shear wave velocity but had minimal effect on electrical resistivity. The collapsibility and friction angle of the soil increased with increase in gypsum. The information derived from the geophysical and geotechnical tests was used to develop statistical design equations and correlations to estimate gypsum content and soil collapse potential.

Through large sculptural works that are often caricatures of representational objects, my work explores the complicated moments and tangled histories of childhood Jewish schooling in Winnipeg and travels to Israel and Palestine as an adult. My thesis exhibition Collapse, as well as most of my graduate work, examines my investigation through manmade constructions that control and restrict or unite and connect the movement of others. Sculptures about a destroyed bridge’s imagined longing for exotic places, a giant onion serving as a resuscitation mechanism against tear gas or a construction crane to Armageddon are some examples of work that explore the poetry I find in dichotomies, and serve as a series of recollections that negotiate experiences beyond full understanding.

This project is an active exploration of subjectivities through the medium of weaving. In a narrative illustrated with woven works, the emotional trajectory of this person of mixed cultural background through Swedish society is described. First, the work is contextualized in terms of the larger politico-cultural-discursive context, entitled the outside. It is then positioned in terms of the individual context, the inside, largely dramatized as the developments in the art of western tapestry in the past century. This culminates in the final works, three of which are presented in the final exhibition. They are entitled monads, the etymology of which, in Greek, relates to the words one, alone, or singularity. Each is a conceptual microcosm proposing a different light distribution scheme. They are imprints of alternative actualizing tendencies. There could only be one; at the end of the experiment, Schrodinger’s cat is either dead or alive. The collapse involves the very structure of the ground, and is therefore embedded directly into the weave structure. But remember, each act of observation is an irreversible disturbance to the system. In the interpretation of the primary emanation arises difference, but in which direction will the pendulum swing, and on what forces does its motion hinge? Do subjectivities follow the locality assumption? Do you produce subjectivities or do they produce you?

Le renforcement des sols au moyen des geosynthetiques est en constante evolution. Cette technique, de part sa simplicite et son cout de mise en oeuvre modere, a deja atteint une certaine reconnaissance pour differentes applications telles que les murs de soutenement renforces (porteur ou non). Un programme de recherche (r. A. F. A. E. L. ) regroupant differents organismes (sncf, scetauroute, bidim geosynthetic s. A. , lrpc, lirigm) a ete mis en oeuvre pour developper une technique de renforcement par geosynthetiques sous les assises ferroviaires et autoroutieres dans les zones a risque. Des remblais experimentaux en vraie grandeur, sollicites par des effondrements localises, ont ete realises sur le site experimental d'eurre (drome) pour contribuer au developpement d'une methode de calcul appropriee a ce type de renforcement. Le dimensionnement des differentes structures experimentales, a pu se faire grace au developpement d'une formulation numerique originale en trois dimensions, d'un element de nappe textile par la methode des elements finis. Des etudes parametriques portant sur la nature du textile, du sol et des conditions d'ancrage sont presentees pour justifier des dispositions techniques retenues. La comparaison des resultats experimentaux et des calculs previsionnels, est tout a fait satisfaisante et montre les avantages et les limites d'une telle solution de renforcement.

The thesis is concerned with the modelling of urinary motion during bladder collapse and is mathematically based. The bladder model as a collapsing vessel is developed as a step towards complementing use of nomograms. Urine motion inside is taken as unsteady flow of incompressible fluid, while the dimensions and collapse rate of the vessel are prescribed using data which is close to realistic biological values. Evolutions of velocities, volume ow rates and effects of the collapse rate are examined. An introduction is made which includes lower urinary tract urodynamics as well as the unique feature that the bladder changes shape and size substantially compared with other vessels. An investigation of simple two-dimensional shapes takes place in chapter two, along with limiting cases for thin vessels. Chapter three analyses simple axisymmetric shapes especially the sphere because of its relevance in addition to its fundamental nature. Development of a numerical scheme is addressed in the next chapter to tackle more complex shapes through the boundary element method and an iterative finite difference scheme with emphasis on flexibility of approach. An extension to more advanced structures of the vessel is constructed in chapter five by means of a concise boundary condition and shape definition. Chapter six takes the work a step further as the approach is applied to axisymmetric configurations. While in an appendix, an extension to implement full viscous effects is then inspected. Finally, further work is discussed in the conclusion.

A numerical approach to including electromagnetism with general relativity is developed using GRAXI as a starting point. We develop a mathematical model describing electromagnetism coupled to a scalar field in an evolving axisymmetric spacetime. As there are numerous formulations of electromagnetism, we evalute different formulations in a limited flat space case. The full curved space system is then developed, using the flat case as a guide to implementing electromagnetism. This model is then implemented using GRAXI as a code base.

This dissertation examines the collapse of masonry structures in response to large support displacements and horizontal ground accelerations. There are two main classes of masonry structure: arches that thrust, and supporting elements, such as walls and buttresses, which resist the thrust. This dissertation analyses the safety of arches and buttresses and identifies the resulting collapse mechanisms due to support displacements or horizontal accelerations. In particular, this research investigates the stability of a masonry arch supported on buttresses and the conditions necessary for collapse to occur. Engineers are frequently asked to determine the safety of masonry structures that have been severely distorted over the years, often due to subsidence or other long-term movements in the foundations, and this dissertation provides guidance in the assessment of such structures. The resistance of masonry buttresses to high-level horizontal loads is examined. In the case of failure due to overturning, a fracture will develop in the masonry, significantly reducing the resistance of the buttress. The capacity is further reduced by outward leaning of the buttresses, a common source of distress for masonry structures due to movements in the supporting foundations. Based on these considerations, new measures of safety are proposed for buttresses under horizontal loading. Outward leaning of the buttresses increases the span of the arch or vault. Spreading supports will cause large deformations in the arch, which increase the horizontal thrust of the arch and may lead to collapse. In addition, lateral ground accelerations can cause the collapse of arches. The influence of seismic action can be approximated to first order by equivalent static analysis to determine the initial collapse mechanism. These problems are analysed for circular masonry arches, and the collapse conditions are identified for various geometries. The findings are combined to investigate the stability of the masonry arch supported on buttresses. The safety of the system is examined by studying the influence of imposed displacements. As the buttresses lean, the thrust of the vault increases and the resistance of the buttress decreases. The collapse mechanisms are identified for both the static case of leaning buttresses and the dynamic case of horizontal acceleration. This analysis illustrates that the arch will collapse and the buttresses will remain standing in most cases. Based on these considerations, new methods are proposed for assessing the safety of masonry structures and determining the influence of future movements on the stability of existing masonry structures.

This thesis is organized as follows: In chapter 1 the theory of a massless scalar field in curved spacetime is introduced. Furthermore the Bogolubov transformation are discussed. In chapter 2 the Hawking effect is derived with the necessary approximations. Then it is briefly mentioned the problem of the information loss paradox In chapter 3 the contribution of the Hawking radiation to the bi-dimensional stress energy tensor is analyzed. In chapter 4 a generic model of gravitational collapse is analyzed with emphasis on the quantum effects. Then we restrict to the case of the collapse of a thin shell, and the accuracy of the Unruh state approximation is examined. In chapter 5 the proposals that the emission of pre-Hawking radiation could prevent the formation of an event horizon for a collapsing object are analyzed. In chapter 6 the arguments which aim to disprove the possibility that pre-Hawking radiation could prevent the formation of a black hole are discussed. Then is questioned the existence of pre-Hawking radiation.

The first stars, galaxies and black holes in the universe produced large quantities of ionising UV radiation; forming H II regions in the neutral gas before the Epoch of Reionisation (EoR). These ionisation fronts will have come into contact with overdensities in the surrounding Intergalactic Medium (IGM), including haloes which were in the process of collapse. Previous studies have shown that the feedback processes on these secondary haloes can either disrupt the gas, or induce further cooling from the formation of molecular hydrogen. The ionising source will eventually die and create a defunct H II region, which expands into the surrounding neutral IGM. Minihaloes at the edge of these defunct H II regions are particularly susceptible to positive feedback due to not having been photoevaporated like their counterparts further inside the ionised volume. In this thesis, numerical simulations of minihaloes at the edges of H II regions formed by the first luminous objects before the EoR are presented. A methodology of including secondary ionisations from high energy photons is also implemented into the radiation hydrodynamical code ZEUS-RT. The interaction of differing spectral index sources with minihaloes including secondary ionisation is discussed. The secondary ionisations show the greatest effect for hard spectral sources with a large fraction of high energy photons; where a decrease in photoheating and an increase in ionisation rate is found at the outer reaches of the ionisation front (I-front). The increased ionisation rate lowers the optical depth of the gas for subsequent photons, and thus reduces the trapping of I-fronts in high densities found in the minihalo cores. The ratio of the free electron fraction to the temperature in the core of the minihaloes is found to constrain the resulting evolution. A high ratio is correlated with the creation of molecular hydrogen, which can then induce further cooling and the collapse of the system.A large parameter suite of 3780 two-dimensional minihalo models utilising radiative hydrodynamical simulations with 12 species and a coupled reaction network, including H2 cooling, HD cooling, Lyman-Werner radiation and secondary ionisation is performed. The parameter space includes: the spectral index representing different sources such as quasars or galaxies, the mass of the minihaloes from 105 - 106 Mʘ, the redshift of ionisation from z ~ 10 - 30, and other factors which denote the position of the minihalo relative to the boundary of the H II region. Minihaloes with average core densities of n0 = 2 - 10 cm-3 show almost unanimous positive feedback, while the majority of minihaloes under this average density are disrupted. Minihaloes with core densities above this value generally would have collapsed in isolation anyway, but are found to not be delayed by the I-front. The H2 fraction in the minihalo gas is also increased in models with no blowout by factors between 2 - 100 times that of an isolated minihalo. This is especially significant for lower redshift, z ≤ 15, minihaloes. Finally, a parameter suite of larger 106 - 107 Mʘ minihaloes results in the creation of self-gravitating clumps of gas moving out of the dark matter potential. The gas core is compressed by the I-front, enriched with molecular hydrogen, and ejected by the pressure front after the source dies. These "baryon bullets" could be progenitors of primordial globular clusters found in the haloes of galaxies today. Properties such as old stellar populations and the lack of dark matter haloes can be explained by this radiative ejection method. The dynamical nature of these interacting systems and diversity of subsequent evolution suggest that minihaloes less than 108 Mʘ are important in the early formation history of the universe, and in determining the constraining parameters of the EoR. The feedback mechanisms investigated, and secondary ionisation physics, should be included in astrophysical simulations and analytical calculations determining the evolution of the universe at this critical epoch.

The progenitors of core-collapse supernovae are stars with an initial mass greater than about 8M⊙. Understanding the evolution of these stars is necessary to comprehend the evolution and differences between supernovae. We have constructed new and unique opacity tables to increase model accuracy during the latest stages of stellar evolution. We have investigated how initial mass, initial composition and mass loss affects the progenitors and their populations. There are many prescriptions for mass loss. Different research groups use their preferred rates. We have compared 12 different prescriptions and determined which provides the best fit to observations. We use our preferred mass-loss scheme to make suggestions as to the source of the differences between supernova types from our progenitor models. Binary evolution is considered in order to search for low luminosity SN progenitors and progenitor types not possible from single stars. Removal of the hydrogen envelope is more common and we find quite different hydrogen deficient SN progenitors. We discuss the implications of our binary models for ultra-luminous X-ray sources and gamma-ray bursts. We present an estimation of the mass distribution for black holes at various metallicities showing that massive black holes are not formed until very low metallicities. Finally we combine the single star and binary results to determine their relative populations and compare to observations. However it is not possible to draw many firm conclusions because of the uncertainty in observations to date.

Soil collapse is amongst one of the most significant ground related hazards. A collapsible soil, in particular loess, typically has an open-structure and collapse occurs when as a consequence of the addition of water and/or load the particles rearrange to form a more dense fabric. Collapse leads to a suite of problems for buildings and infrastructures built on or in collapsing soil. Treatment to mitigate collapse often involves in densification. However, such approaches have been reported not always effective enough to combat the problem. This stems from a lack of understanding of soils’ geochemistry and structure, the result of which is an oversimplification of complex geotechnical and geological interactions. An important example of such limited knowledge is the increasing evidence of restoration of the collapsing structure upon wetting-drying cycles, which is widely ignored in the current compaction practice. This research aims to first identifying collapse micro-mechanisms in fine-grained soils, examining the contribution of a handful of soil constituents in collapsibility, and finally developing a practical tool for ground engineers to evaluate the efficiency of the current compaction practice for systematically classified fine-grained soils, and to take modified/novel earthwork approaches where the current practice fails to fully remove the collapse risk.