Dissertations / Theses on the topic 'Soil behaviour'

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.

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.

The consolidation behaviour of gassy soil has been studied in a programme of experimental and theoretical research. This research is of particular importance to the offshore geotechnical industry as the presence of gas in the seabed can have a dramatic effect on the material properties of a marine sediment. Initial numerical modelling based on existing unsaturated soil theory combining the gas and the water phase into a compressible fluid in the pores of compressible soil skeleton failed to simulate the soil behaviour previously observed experimentally at Oxford. Therefore, there was scope for further study in this field. Chapters 2 to 4 describe the experimental preparation, consolidation technique and experimental results of the two series of tests on artificially prepared gassy soil samples. The results of these tests indicated that the gas appeared to be affected by the total stress rather than the pore water pressure, with the saturated soil matrix outside the gas voids being controlled by the consolidation stress. Chapter 5 presents the one-dimensional numerical modelling of the experimental results. Poor simulations were again made using compressible fluid theory. Treating the gas as compressible solid inclusions embedded in a saturated soil matrix, however, resulted in excellent simulations of the observed pore water pressures and settlements. Chapter 6 attempts to explain the results of the experimental and numerical modelling in terms of elastic and plastic soil behaviour. This includes the introduction to the double compressibility model in which the deformation behaviour of the saturated matrix is governed by changes in consolidation stress, whereas that of the gas is governed by changes in total stress. Chapter 7 presents the development of the governing gassy soil consolidation equations under both plane strain and axisymmetric conditions. Chapter 8 describes the approximation of the governing consolidation equations using the Galerkin finite element method in terms of nodal displacements and pore water pressures. The resulting finite element approximation is subsequently formulated for rectangular elements under plane strain and axisymmetric conditions in Chapter 9. The remainder of the thesis describes the structure of the finite element model DCFEM2 and the constitutive relationships that are required for such a model. The code is verified with existing analytical solutions and then is used to simulate the observed gassy soil behaviour under laboratory and field conditions.

Long-term low-level ingestion of cadmium (Cd) causes human health problems, and in Australia, vegetables supply ~40% of the Cd in the typical diet. Plants take up Cd from the soil; however, the uptake is poorly predicted by simple soil tests, such as the total concentration of Cd (Cdt). Therefore, a greater understanding of Cd behaviour in soils is needed to improve the prediction of Cd uptake by plants and open a new path to minimise the risks for human health. The objectives of the research in this thesis were to: identify key soil properties affecting Cd behaviour, identify/develop selective methods to measure them, and to formulate a conceptual model of Cd partitioning. These objectives were based on the hypothesis that empirical modelling informed by a better understanding of Cd chemistry would accurately describe Cd partitioning in soil. To test the hypothesis, the key properties were measured on soils from the peri-urban fringe of Greater Sydney (n = 41) and a series of models of increasing complexity were fitted to the data. A model with three explanatory variables— log10 Cdt, pH and log10 ECEC (effective cation exchange capacity)—explained 94.6% of variation in log10 CdCa (the concentration of Cd in solution in a suspension of soil in 10 mM CaCl2), which strongly supported the hypothesis. The study also indicated that the explanatory variables, Cdt, pH and ECEC, may describe Cd behaviour in many soils, and that for these general models, partition coefficients, such as log10 (Cdt/CdCa), are unsuitable dependent variables. The preceding model used Cdt as an explanatory variable, notwithstanding that labile Cd (CdE) was mechanistically preferable. However, CdE can only be measured using isotopic techniques: a requirement that has constrained the evaluation of CdE as an index of Cd behaviour and bioavailability. Therefore, a simple proxy measure of CdE was investigated. The literature indicated that solutions of chloride salts might selectively extract CdE, and Cd extracted into 1 M NH4Cl (CdNH4Cl) was compared with CdE measured by stable isotope dilution ICPMS. For 23 soils from the partitioning study, 1 M NH4Cl failed to completely extract CdE, unless the pH was less than 5. The cause(s) of this effect will be investigated with the aim of developing a universally applicable measure of CdE that does not require isotopic measurements. All models of Cd uptake by plants rely on soil properties measured on homogenised samples, although the distribution and bioavailability of Cd vary spatially in the field. Were such variability to increase at the micro-scale, its effects could erode the accuracy with which models could predict Cd behaviour and uptake. Consequently, I tested whether the distribution of Cd could be mapped by using synchrotron micro-x-ray fluorescence spectroscopy (micro- XRFS): the most sensitive method of observation. The soils examined contained 0.3–6.4 mg Cd/kg, i.e. were typical agricultural soils, and one was spiked to ~100 mg Cd/kg. Micro-XRFS mapped the Cd in the spiked soil, and in one particle in the other soils. For typical agricultural soils, the sensitivity realised in this study would have been sufficient to characterise the average Cd binding site, but fell at least 10-fold below that needed to map the Cd distribution in them. The research satisfied the objectives, advanced knowledge of Cd behaviour in soils, and provided new research leads. These leads include the possibility of developing general models of Cd partitioning in soils, derivatives of which may predict Cd uptake by plants. The accuracy of these models may be strengthened by the use of CdE as an explanatory variable, but may be weakened by the effects of in situ variation in the distribution of Cd. The benefits to human health of agricultural practices that decrease dietary Cd justify continuation of research to develop models that accurately predict Cd uptake by plants.

Thesis (Ph.D.) -- University of Western Sydney, 2008.
A thesis submitted to the University of Western Sydney, College of Health and Science, Centre for Plant and Food Science, in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliographical references.

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.

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.

Soils of the Argentine Pampas have been developed over same parent material (loess), but evolved under different topography and land use. This led to different soil structural behaviour. In the flooding Pampa of Argentina soils (Solonetzes) are flooded each winter-spring and dried each summer, and are grazed by livestock all year round. Little is known about cattle trampling effects under these environmental conditions. In the nearby rolling Pampa, there are silty loams affected by physical deterioration and water erosion losses after long term conventional tillage (CT). After continuous zero tillage (ZT) these soils often develop shallow compaction. Little is known about abiotic and biotic mechanisms of structural recovery. The general objective of this thesis was to analyze comparatively natural and made-man factors affecting soil structural behaviour in soils with similar parent material (loess) and vegetation (grassland), but later affected by different relief and soil use factors. In the flooding Pampa results showed the occurrence of significant soil volume changes by swelling and shrinking. Soils swell during flooding because of a process of air entrapment. Livestock trampling causes the mechanical destruction of surface macropores in summer when soil dries. The regeneration of damaged pores takes place during flooding, when soils swell at maximum. Droughts -and not floods- cause negative environmental effects in this area. In the rolling Pampa similar soil macropore volumes were determined in pasture, CT and ZT situations, showing none effect from soil management. Topsoil hardening was often found after short term ZT. Results from a greenhouse experiment showed that aggregate stabilization requires a previous fragmentation by short wetting-drying cycles. Clod shrinkage curves and soil cracking studies showed that silty loams do not have the expected poor response to W/D cycles. However, their air filled porosity increases little during drying. Results showed topsoil aggregation to be mainly abiotic in the flooding Pampa, and abiotic and biotic in the rolling Pampa, showing different structural behaviour in soils evolved from same parent material but different relief and land use.

A study was made of the physical properties of a number of structurally sensitive soils some of which exhibited behaviour characteristic of hard-setting soils (soils which when wet slump and set hard, on drying presenting problems in terms of ease of cultivations and root growth). Work concentrated on an examination of soils of the Wick series at two sites at the Institute of Horticultural Research, Wellesbourne, where there is a documented history of consistent differences in crop yields between sites. The worse site (Big Ground) had been intensively managed for considerably longer than the better one (Plum Orchard). Dry bulk density measurements over the growing season suggest that slumping occurred on both sites. Big Ground had the greatest bulk density (typically over 1.65 g/cm3). Field and laboratory penetrometer measurements have shown that under relatively dry (an 8% moisture content) conditions roots would experience severe mechanical impedence on both sites. Root counts at final harvest showed that conditions for rooting were considerably worse in Big Ground where all roots were confined to the top 30 cm. Root growth was better in Plum Orchard and was concentrated in between peds, which did not exist at Big Ground. Laboratory strength (unconfined compressive and indirect tensile) and friability measurements on equilibrated samples also showed up differences between the two sites; the greates differences existing between 1 and 10 bar tension with Big Ground samples exhibiting the greatest strengths and least friabilities. On both sites strengths were observed to increase sharply for a comparatively small decrease in moisture content. Implications of these results are discussed with reference to ease of cultivation and rootability. Another light texured soil from Elgin, known for its tendency to erode, was chosen as a contrast to the Wellesbourne sites. Soil at this site was shown to have much less of a tendency to slump and to create problems for root growth, compared to the Wellesbourne sites. The Elgin soil was also considerably weaker, and the sharp increase in strength observed at Wellesbourne was not observed in Elgin. A new test for water suspendable solids, performed on the Wellesbourne and Elgin soils as well as on 5 other soils known for their structural instability showed that, with the exception of the Elgin soil, a large amount of silt sized material could be brought into suspension with little soild disturbance. An explanation for hard-setting behaviour which is based on those results is suggested.

The research described in this thesis concerns the use of transparent soil in physical modelling to better understand theoretical and analytical analyses of a geotechnical engineering problem. One of the more recent evolutions in the field of geotechnics is the use of geosynthetic materials as reinforcement to improve the shear resistance of soil, and ultimately provide reinforcement to earth structures. Their application in engineering earthworks has increased significantly in recent years. When designing reinforced earth structures, a vital aspect is to understand the interaction between the reinforcement and the compacted soil as this governs the overall stability. The main function of the reinforcement is to redistribute the stresses within the soil structure in order to enhance the internal stability of the reinforced soil structure. The reinforcement undergoes tensile strain as it transfers loads from unstable to stable zones of the soil. The most common example of soil-geogrid interaction research is to investigate pull-out capacity. The lack of knowledge of interaction mechanics between soil and reinforcement has considerable impact on the ability to implement rigorous analytical solutions, or to assign suitable parameters for interface elements in numerical modelling. By using classical pull-out, previous researchers have indicated that the interface factors vary between 0.6 - 0.8 (FHWA-NHI-00-043, 2001); hence, it is likely that many designs over predict the possible resistance that may be generated. Furthermore, in the absence of field validation, there is uncertainty as to how representative small scale pull-out tests reflect the likely behaviour that would prevail in the prototype structure. The transparent soil utilised here is representative of coarse soil and allows nonintrusive measurement of soil displacement on a plane highlighted by a sheet of laser light, captured by a digital camera. This enables the measurement of the displacement of the soil on the target plane by using the image process technique “Particle Image Velocimetry”. This technique allows the observation of the interaction between soil and geogrid, and the shear and pull-out boundary which is mobilised around the geogrid. The principal aim of this research is to investigate the detailed interaction between granular soil and geosynthetics, and to provide a better understanding of the interaction both analytically and numerically. To achieve this aim, this research is separated into two key areas: 1. Analytical modelling of the interaction between soil and geogrid to assess the degree of uncertainty inherent in the methods; 2. Advanced visualisation element tests using transparent soil technology and Particle Image Velocimetry (PIV) to directly observation of the patterns of strain between the soil and reinforcing material.

Copies of author's previously published articles inserted. Bibliography: leaves 173-196. The objective of this thesis is to investigate the factors affecting swelling and dispersion of alkaline sodic soils containing lime and the ways to manage these soils to improve their physical condition. Studies on pure clay systems are included to understand the fundamental process involved in swelling and dispersion of pure and soil clays.

Natural draught cooling towers belong to a category of exceptional civil engineering structures. These towers are an effective and economic choice among all technical solutions for the prevention of thermal pollution of natural water resources caused by heated cooling water in various industrial facilities. They are therefore widely used in most electric power generation units, chemical and petroleum industries and space conditioning processes. The cooling tower shell is the most important part of the cooling tower, both in technical and financial terms and also the most sensitive, since its collapse would put all or part of the cooling tower out of action for a considerable length of time. In this thesis, the 2D and 3D behaviour of soil-cooling tower-interaction, via the idealisation of the structure and soil on the resulting parameters, have been investigated, taking into consideration the effect of temperature changes in the cooling tower on the simultaneous interaction of the cooling tower and underlying soil. The temperature effect has been considered because it plays an important role in the design of the cooling towers. The capabilities of the two-dimensional Geotechnical Finite Element Analysis Program (GeoFEAP) have been updated in this project and the new version has been referred to as GeoFEAP2. New modelling capabilities and the ability to model 3D problems, with accompanying postprocessing features, were introduced, including 3D first order 8-noded hexahedrons. In addition, the Drucker-Prager yield criterion was programmed in GeoFEAP2 to model the elasto-plastic behaviour of the soil. A new 4-noded quadrilateral flat shell element, based on discrete the Kirchhoff's quadrilateral plate bending element, was also added to the software to model the elastic behaviour of the cooling tower shell. Furthermore, this element was modified to accommodate a temperature profile. The new software (GeoFEAP2) was then validated for soil behaviour and using several standard widely-used benchmark problems and the results compared well with the analytical and/or numerical results obtained by other researchers. A 3D finite element model was created, comprising the cooling tower, columns support, foundation, and elasto-plastic soil behaviour. The analyses of soil-cooling tower-interaction in this thesis have indicated the need to model the soil and structure as a combined problem, rather than by applying loads onto soil as geotechnical engineers' model, or by assuming the soil comprises springs and model the cooling tower, as structural engineers' model. The results have shown how unrealistic the latter two approaches are. In addition, the analysis necessitates the incorporation of thermal effects when modelling cooling tower problems. Moreover, from a design point of view, it has been recommended that circular footing with two cross-columns is better than pad footings and/or one column. Several other conclusions have been made that would improve the modelling of soil-cooling tower-interaction. Furthermore, the designer needs to ensure that enough modelling of soil conditions is done and an extensive site investigation is required to ensure that the variation in soil properties is represented correctly. Finally, the engineer needs also to ensure that the site tests performed to measure shear strength with depth via drilling and other methods needs to go deep enough into the ground to ensure that enough site information is available when designing the cooling tower.

Measured data from five geotechnical structures have been back analysed to determine, in each case, the set of material parameters that will permit a reasonable match to the observed pre-failure foundation response. Back analyses have been performed using simple constitutive soil models (Tresca, Mohr-Coulomb and modified Cam clay) as implemented in the finite element analysis package CRISP90. Trial loading data are available from: 1. The rapid loading to failure of a soft clay soft foundation through a rigid reinforced concrete slab. 2. The loading to failure of a soft clay foundation via the rapid construction of a trial embankment. 3. The long-term behaviour of a soft clay foundation loaded via a stable trial embankment. 4. The behaviour of two long span, flexible culverts under (granular) backfill and imposed loads. From comparison of the computed and observed responses conclusions have been drawn which have implications for the general application of finite element analysis to geotechnical problems; parameter selection or numerical analyses; and the essential requirements of the soil model for predicting soil behaviour. In chapters 3, 4 and 5 the main concern of analyses was to reproduce the observed settlements, lateral displacements and excess pore water pressures induced within the soft clay foundations. Analyses primarily concentrated on the use of the modified Cam clay soil model. Particularly in chapter 3, the ability of modified Cam clay to predict the essential elements of the foundation behaviour was reasonable. However, in chapters 4 and 5 predictions of lateral displacements and excess pore water pressures were poor. More accurate estimates of the observed lateral displacements and excess pore water pressures were obtained using empirical methods (hand calculations). The reason for the different quality of lateral displacement and excess pore water pressure predictions is thought, mainly, to be due to incomplete saturation of the soft clay at the trial embankment test site. The influence of incomplete saturation is thought to initially force a drained foundation response, which in the short term will give rise to smaller lateral displacements and excess pore water pressures than those predicted from fully undrained analyses. In the long term, further improvement of embankment lateral displacements and excess pore water pressures may be achieved through considerations of viscosity

This thesis presents the kinematics occurring during lab-based dynamic compaction tests using high speed photography and image correlation techniques. High speed photography and X-ray microtomography have been used to analyse the behaviour of sandy soil subjected to dynamic impact. In particular, the densification mechanism of granular soils due to dynamic compaction is the main theme of the thesis. High speed photography and digital image correlation (DIC) techniques have enabled the deformation patterns, soil strains and strain localisations to be observed. Image correlation and X-ray scans revealed the formation, rate and growth of narrow tabular bands of intense deformation and significant volumetric change and provided answers towards a better understanding of the densification mechanism in dry granular soils due to dynamic compaction. As a quantitative tool, high speed photography has allowed the propagation of localised deformation and strain fields to be identified and has suggested that compaction shock bands control the kinematics of dynamic compaction. The displacement and strain results from high speed photography showed that soil deformation in the dynamic tests was dominated by a general bearing capacity mechanism similar to that widely stated in classic soil mechanics texts. Comparative static loading tests have been conducted to enable the dynamic effects to be clearly distinguished. This has enabled the densification process taking place below the soil surface to be investigated and identified. Simulations of the physical models were carried out using LS-DYNA finite element formulations for comparison and verification purposes. The FE simulations verified the general characteristics from the photography findings. However, simulation results were unable to predict the exact details of the strain localisation due to surface impacts during physical model tests.

This thesis examines the pre and post failure deformation behaviour of landslides in cut, fill and natural soil slopes, and of the deformation behaviour of embankment dams. The deformation behaviour of landslides and embankment dams have been analysed from a database of case studies from a number of classes of slope (and dam) and material type. The database included some 450 landslides in cuts, fills and natural slopes, and some 170 embankment dams. For landslides in soil slopes, methods and guidelines have been developed for use in the analysis, evaluation and prediction of the pre and post failure deformation behaviour. They take into consideration the factors influencing and the mechanics controlling the deformation behaviour for the classes of slope and material types, which are different for pre and post failure. Pre-failure deformations are largely controlled by the effective stress conditions within the slope, changes in the boundary conditions and the response of the soil to those changes in boundary conditions. Whether the soil, under the effective stress conditions imposed within the slope, is contractive (and saturated or near saturated) or dilative on shearing, has a significant influence on the pre failure deformation behaviour. The post failure deformation behaviour is strongly influenced by the mechanics of failure (including whether the soil is contractive or dilative on shearing), the source area slope angle, the downslope geometry, the orientation of the surface of rupture, the material properties and slide volume. Guidelines are presented for prediction of 'rapid' and 'slow' post failure velocity. For embankment dams, methods and guidelines have been developed for evaluation and prediction of the deformation behaviour during and post construction for selected embankment types. They take into consideration the influence of material type and placement methods, material strength and compressibility properties, embankment zoning geometry, embankment height, and reservoir operation, amongst other factors. Guidelines have been developed to assist in the identification of 'abnormal' deformation behaviour, which can be related to internal deformations or a marginal stability condition and the onset to failure.

Not much has research work been done so far on temperature-related behaviour of clays. This theme has not received much attention of research workers in this field for a long time until the late 1960s when Campanella and Mitchell published their paper on "Influence of Temperature Variations on Soil Behaviour" in 1968 (Campanella and Mitchell, 1968). What followed was a special conference on this subject held in Washington in 1969, addressing a variety of research results in this field at that time. However, the interest of most research workers in the following two decades has been in soil models and their numerical implementation. Most research funds have been channelled towards studies concerning basic soil properties and the implementation of the results of research than to other topics in the same time. In recent years, rapid industrialization and implementation of many military technologies into civil industries have taken place in many western countries and a few other countries in Asia. This gave rise to a variety of problems related to the disposal of nuclear waste particularly in the late 1980s. A series of studies regarding disposal problems of nuclear waste were then carried out in Italy and the United States (Hueckel et al, 1990). In Australia, the first project related to this topic was awarded in 1991 to the Centre for Geotechnical Research (CGR) at School of Civil and Mining Engineering, University of Sydney. This thesis contains the results obtained from triaxial tests performed at different elevated temperatures using a new triaxial apparatus called HTTA (High Temperature Triaxial Apparatus) specially designed for and forming part of, the work in this research. The thesis also contains a comparison of the experimental results and the predictions by different Cam-clay models including the revised Camclay model developed in this research. Specimens of a remoulded clay, Kaolin CIC, have been tested at various I temperatures ranging from ambient temperature of 22±2°C to 100±5°C with two triaxial apparatuses. The first apparatus for tests at ambient temperature is a Bishop- Wesley-Type hydraulic triaxial apparatus; the other is a modified triaxial apparatus specially tailored and assembled for performing triaxial tests on the specimens at various elevated temperatures. The triaxial tests on the specimens were conducted at room temperature as well as at two elevated temperatures, namely 50°C and 100°C. Stress-strain response of the specimens at different temperatures was observed. Attempts have been made in different ways to investigate whether soil properties of the selected clay would change with temperature. Further, the attempts made were also to see what have been changed in the stress-strain behaviour of the clay at different elevated temperature. Then, the test results from different elevated temperatures were compared with those obtained from the tests at room temperature; and also compared with the predictions by the Cam-clay models.

The most recent version of the New Zealand design and loadings standard eliminated a clause for the design of rocking foundations. This thesis addresses that clause by presenting a strong argument for rocking shallow foundations in earthquake resistant design. The goals of the research were to perform large scale field experiments on rocking foundations, develop numerical models validated from those experiments, and produce a design guide for rocking shallow foundations on cohesive soil. Ultimately, this thesis investigates the nonlinear rotational behaviour of shallow foundations on cohesive soil. Field experiments were performed on an Auckland residual soil, predominantly clay. The experiment structure - a large scale steel frame - was excited first by an eccentric mass shaker and second by a quick release (snap-back) method. The results show that rocking foundations produce highly nonlinear moment-rotation behaviour and a well defined moment capacity. A hyperbolic equation is proposed in Chapter 4 utilising the initial stiffness and moment capacity to predict nonlinear pushover response. The results show that the initial stiffness should be based on an 'operational soil modulus' rather than a small strain soil modulus. Therefore, the reduction factor from the small strain modulus was around 0.6 for the experiment testing. Additionally, the experiments showed that rocking foundations demonstrate significant damping; snap-back experiments revealed an average damping ratio of around 30%. Experiment data validated two numerical models developed for this study: one, a finite element model in Abaqus and the other, a spring bed model in OpenSEES. The models showed that both forms of nonlinearity in rotating shallow foundations - geometric nonlinearity and material nonlinearity - should be considered in shallow foundation analysis. These models also confirmed the need for an 'operational soil modulus' on shallow foundation rocking, and analysis of varying vertical loads suggested that this reduction factor is dependent on the vertical factor of safety of the foundation. Lastly, two design methods are presented, a displacement-based method and a forcebased method, and two examples of rocking shear walls are given. The displacementbased method is the recommended option, and it is shown that design displacements and rotations compare well to time history analyses performed using the validated OpenSEES model.

Understanding the mechanisms by which any engineering structure resists load is an essential requirement for its consistent and reliable design. The axial resistance which can be mobilised by piled foundations in liquefiable soils when subjected to strong shaking remains highly uncertain, and a number of piled foundations have failed in strong earthquakes as recently as 2011 . The lack of visible foundation distress in many such cases indicates that failure can occur as a result of the loss of axial capacity during an earthquake, as opposed to the laterally-dominated failure modes which have been the focus of the research community for the last 20 to 30 years. In this thesis, a series of dynamic centrifuge experiments have been carried out to establish how the distribution of axial loads along the length of a pile changes during a strong earthquake. In each test, a 2 × 2 pile group was installed such that its tips were embedded in a dense sand layer which was overlain by liquefiable soil. The tests examine the effects arising from the hydraulic conductivity in the bearing layer, the influence of axial pile cap support and finally whether there are any differences in the behaviour of nominally jacked or bored piles under seismic loading. The pile cap has been shown to play a substantial role in supporting axial loads during strong shaking. In cases where the pile cap was unable to support axial load, the majority of the axial loading was carried as pile end bearing, with some shaft friction being mobilised in both the liquefiable and bearing soil layers as a result of relative lateral displacements between the soil and pile. However, where the pile cap is able to support axial loads, the settlement of the pile cap into the soil led to a dramatic transfer of axial load away from the piles and onto the pile cap. These results imply that where substantial excess pore pressures may be generated at the depth of the pile tip, then the pile caps must be able to support significant axial load. The increased effective stresses below the pile cap were responsible for the mobilisation of shaft friction on the section of pile within the liquefiable layer. However, these piles were unable to mobilise shaft friction in the bearing layer due to the reduced lateral loading on the piles. The axial behaviour of the piled foundations after the end of strong shaking is affected by the recovery of pile end bearing capacity and is therefore strongly dependent on the hydraulic conductivity of the bearing layer. The axial behaviour of nominally bored and jacked pile groups in liquefiable soil deposits are very different under seismic excitation, with the installation process of the latter substantially altering the soil conditions around the tips of the pile, such that in contrast to the bored pile groups, the jacked pile groups did not accumulate settlements until significantly after the strong shaking had commenced. These results imply that the method of installation is an important factor in the seismic response of a foundation, and may be more pronounced for real earthquakes where the number of strong shaking cycles may be more limited than those simulated in the experiments.

Landfill covers are designed as impermeable caps on top of waste containment facilities after the completion of landfill operations. Geocomposite drain (GD) materials consist of a geonet or geospacer (as a drainage core) sandwiched between non-woven geotextiles that act as separators and filters. GD provides a drainage function as part of the cover system. The stability performance of landfill cover system is largely controlled by the interface shear strength mobilised between the elements of the cover. If a GD is used, the interface shear strength properties between the upper surface of the GD and the overlying soil may govern stability of the system. It is not uncommon for fine grained materials to be used as cover soils. In these cases, understanding soil softening issues at the soil interface with the non-woven geotextile is important. Such softening can be caused by capillary break behaviour and build-up of water pressures from the toe of the drain upwards into the cover soil. The interaction processes to allow water flow into a GD core through the soil-geotextile interface is very complex, and have been defined herein as Capillary Related Interface Breakthrough (CRIB). The infiltration test using small column on CRIB conditions for GD in contact with fine grained soils confirmed the development of capillary break at the interface. The effect of water build-up on the interface leads to soil softening in fine grained soils layer and reduce the interface shear strength hence potential instability of the system. Two series of fine grained soil/GD interface shear strength tests conducted to determine the interface shear strength behaviour for a range of soil water contents. The soil softening at the interface due to soaked behaviour show a reduction in interface shear strength and this aspect should be emphasized in design specifications and construction control. Comparison on the main behaviour using field measurements on the trial landfill cover at Bletchley were conducted to increase confidence in the understanding of the implications for design of cover systems.

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
O comportamento de uma escavação grampeada em solo residual de gnaisse foi avaliado por um programa de monitoramento geotécnico do maciço reforçado. Diversas obras estão sendo realizadas no país, sem conhecimentos detalhados sobre as deformações inerentes à técnica e sobre os mecanismos de interação solo-grampo. No Brasil, menos de 10% das obras de solo grampeado utilizaram algum tipo de instrumentação. Esta pesquisa teve por objetivo a análise de uma escavação em solo residual reforçada com grampos. A escavação foi instrumentada para o monitoramento dos deslocamentos do maciço e dos esforços nos grampos. Um extenso programa experimental de ensaios de campo e laboratório foi executado para fornecer os parâmetros geotécnicos utilizados nas análises computacionais. A escavação grampeada teve cerca de 40m de altura, constituindo uma experiência inédita no país e talvez no mundo. Devido a esta altura, os grampos superiores foram instalados com comprimentos de até 24m. O comportamento do talude foi influenciado pelo processo executivo e por uma outra escavação no terreno vizinho. O monitoramento indicou que os deslocamentos do maciço e os esforços nos grampos cresceram significativamente com o avanço da escavação e não cessaram ao final da obra. Os grampos trabalharam predominantemente à tração, com momentos fletores pouco significativos. Os valores de tração estimados na fase de projeto diferiram dos resultados obtidos na instrumentação. A distribuição dos esforços de tração foi influenciada pelas características geológicas do maciço. A tração máxima (Tmáx) teve uma posição variando com a profundidade e a inclinação do talude, e uma magnitude aumentando exponencialmente com o avanço da escavação. A tração na face (To) foi de 0,3 a 0,6 de Tmáx. A resistência mobilizada no contacto solo- grampo não ultrapassou 35% do valor de qs medido nos ensaios de campo.
The behavior of a nailed excavation in gneissic residual soil has been studied by a comprehensive research program, including instrumentation, field and laboratory tests and numerical analyses. Soil nailing is becoming a popular stabilization technique in Brazil. However, a solid knowledge about the soil-nail interaction is still lacking. There are a few studies about the inherent deformations of the reinforced mass and the magnitude of nail`s stresses. In Brazil, less than 10% of stabilization works have some type of instrumentation. The main objective of this research was monitoring and analysing a 40m high soil nailed slope excavation. Due to this unique height, the upper nails were installed with 24m length. The slope behavior was influenced by several factors, such as the construction technique and a subsequent excavation at one adjacent site. The results indicated a significant increase of reinforced mass displacements and of the nail s mobilized tension during the progress of the excavation. These did not cease after the end of the excavation, due to the adjacent work. During and after construction, the nails worked predominantly in tension. Estimated tension loads in the project phase were compared with the instrumentation s results. The stress distribution was influenced by local geology. The maximum axial force (Tmáx) increased exponentially with the progress of the excavation and its position, in each nail, varies with the slope s depth and inclination. The magnitude of the axial load in the excavation face is observed to be between 0,3 and 0,6 of Tmáx. The mobilization of the reinforcement elements was smaller than 35% qs.

Traditionally, void ratio, e has been used as a state variable for predicting the liquefaction behaviour of soils under the Critical State (Steady State) framework. Recent publications show that void ratio, e may not be a good parameter for characterizing sand with fines as the steady state, SS data points move downward in e-log(p) space up to certain fines content termed as threshold fines content, TFC. Thus, it was difficult to apply SS concept on sand with fines as a small variation of fines content may lead to different SS line. Many researchers proposed to used equivalent granular void ratio, e* as an alternative state variable (i.e. in lieu of void ratio, e) in attempt to obtain a narrow trend line for SS data points irrespective of fc provided fc  TFC. The e* is obtained from e. For the conversion from e to e*, one need a parameter b which presents the active fraction of fines in overall force structure of sand. However, predicting the b is problematic. Most, if not all, of the b reported were determined by case-specific back-analysis, that is, the b-value was selected so that the test results for a given sand-fines type could be correlated with the equivalent granular void ratio, e* irrespective of fines content. This thesis examines the factors that affecting the b value by examining published work on binary packing. This leads to a simple semi-empirical equation for predicting the value of b based onparticle size ratio,  and fines content, fc. Published data and experimental results on Sydney sand appears to be in support of the proposed equation. The single relation of SS data points in e*-log(p) space for sand with fines is referred as Equivalent Granular Steady State Line, EG-SSL. The EG-SSL is then used to define the equivalent granular state parameter,*. A good correlation observed between * and q-p, q- q responses in undrained shearing. The e* and * are also used to modified a state dependent constitutive model. Seven model input parameters are needed in addition four to critical state input parameters. These parameters are obtained from drained test. The model is used to predict q-pand q- q responses for flow, non-flow and limited flow behaviour for 0% to 30% fines contents. The model predictions are in good agreement with experimental results. The effect of fines types (in terms of plasticity and angularity) on the prediction equation of b are also examined with four different types of fines. A negligible effect of fines type on the prediction equation of b is observed. The link between monotonic and cyclic loading behaviour for sand with fines are also examined with emphasis on cyclic instability and strain hardening behaviour after quasi steady state, QSS for a range of fines contents (provided that fc < TFC). It is found that a single set of rules could be used to correlate monotonic and cyclic behaviour for a range of fines contents at same *.

The work described in this thesis was firstly concerned with developing and evaluating automated soil testing equipment and associated instrumentation. The equipment consists principally of a triaxial stress path cell of the Bishop-Wesley type, a microcomputer and two pressure controllers. Inductive displacement transducers have been mounted inside the cell to measure axial and radial strains locally on the specimen boundary and axial strains between the end caps. The local axial strain measurements have proved superior to the end cap measurements which can be adversely affected by bedding errors and misalignment of the transducers relative to the loading axis. Following the development, the system was used to investigate the stress-strain behaviour of Cowden Till, particularly at small strains (0.01 - 0.10%). Cylindrical blocks of 250mm diameter were retrieved from the site and stored under isotropic stress. Eight specimens of 100mm diameter were trimmed from these blocks and subjected to either a drained or undrained compression test under load-controlled conditions. Cowden Till has been shown to exhibit strongly non-linear stress strain behaviour, even at small strains, and most of the shear strain is irreversible. The stress-strain characteristics were in acceptable agreement with those derived from a 865mm diameter plate loading test with under-plate instrumentation. Although the interpretation of the plate test is still being investigated, it is concluded that plate tests provide no better information about the stiffness of the material than triaxial tests of the type described in this thesis. The experimental stress-strain behaviour during compressive loading has been compared with the predictions of some mathematical models. The nonlinear elastic model of Atkinson (1973) appears to be applicable to Cowden Till, for which the behaviour is approximately isotropic. Simple stiffness predictions on the basis of critical state soil mechanics are inadequate at small strains. However, the model of Pender (1978) predicts the behaviour reasonably well. (ii) An attempt has been made to analyse the compression (bedding error) which occurs at the end of a triaxial specimen as the axial strain is increased. A quantification of the compression is hindered by the random nature of surface variations and by the limitations of present theories.

To acquire deeper understanding and insights into the mechanical behaviour of fibre reinforced saturated/unsaturated cohesive soils, a programme of work was designed and included. 1) Conducting standard Consolidation Undrained (CU) tests to investigate mechanical behaviour of non-reinforced fully saturated soil. 2) Studying the strength of fibre reinforced clay though unconfined compression tests. 3) Testing the behaviour of unsaturated reinforced soil in unsaturated triaxial tests. 4) Determining the soil-water characteristic curves (SWCC) on soil sample with different fibre content. The investigation was undertaken on a clay of low plasticity index. Samples tested with addition of 1, 3 and 5 % fibre content and different values of matric suction of 50, 100 and 200 kPa, one of the challenges that were encountered in this research are how to prepare homogenous samples. A method for prepared compacted fibre reinforced soils with improved fibre distribution and density profile has been proposed and examined. The test results indicated that waste carpet fibres increase the shear strength of unsaturated clay soils. It was also found that relative increase in strength is also a function of applied suction. An increase in waste carpet fibres was found to reduce the hysteresis of soil. A data analysis conducted on the results of unsaturated tests as a function of fibre content and matric suction. The behaviour modelled was shown to be a perfect fit with the experimental data.

The response of piles and two-pile groups to lateral loading has been studied by field tests and computationally. Due to the lack of field test data and because of uncertainty concerning the pile/soil system it has been suggested that further experimental studies of pile groups under lateral loading should be undertaken. The research was conducted through a series of tests on vertical single piles and two-pile groups at various spacing and pile cap overhang heights, to identify the lateral stiffness, bending moment and axial force distribution. Attempts were also made to measure the in-situ total lateral soil pressure on the pile walls. Piles were designed to behave as "long" pile since most piles used in the U.K. are long and flexible. Piles were instrumented with strain gauges for measurement of bending moments and axial forces. Field tests were conducted in a sand trench using 4.0m long piles. A stiff steel pile cap was used to connect head of the two piles firmly together. Linear elastic back analyses of single pile tests were carried out to estimate the soil modulus profile with depth. Thereafter comparisons were made between the field test results on two-pile groups, published analyses and also a three dimensional finite element analysis. Tests results showed that the lateral stiffness of a two-pile groups tends towards a limit as spacing increases. A similar result was found from predictive and finite element analyses. The ratio between the maximum pile shaft bending moment and horizontal force varied between dry and wet season, being greater in the latter. The ratio between maximum reverse bending moment and horizontal load increased as the pile spacing and the overhang increased. Similar results results were found by finite element analysis. One of the main achievements in this research was the measurement of the axial forces in the vertical piles due to lateral loading. It was found that as the pile spacing increased and pile cap overhang height decreasd the peak axial forces per unit load decreased. Similar results were obtained by three dimensional finite element analysis.

Climate change poses real threats to the sustainability of slopes, particularly in the tropical region of the world. Its effects have caused a greater occurrence of extreme climate events that are reflected in a greater occurrence of slope failure incidents for this region. The hydro-mechanical characteristics of soils linked with climate variation are factors that can explain deterioration in slope stability. Therefore, the ability to analyse the hydro-mechanical behaviour properly is worthy of investigation and this can be done by the use of experimental investigation and numerical modelling using both saturated and unsaturated soil properties. In this thesis, the description of the important effects of climate impacts on slope stability has been made for a failed tropical residual soil slope located in Precinct 9, Putrajaya, Malaysia. Part of the work involved soil sampling for the acquisition of undisturbed soil samples from the slope. Series of advanced saturated and unsaturated laboratory testing for both hydrological and mechanical properties have also been implemented and were used in transient, unsaturated numerical modelling of slope stability analysis (using Plaxis 2D). The results demonstrate that within a slope the mobilised shear strength drops quickly during a rainfall event (due to rainfall infiltration) but recovers much more slowly during drying. This shows how a series of regular rain storms with short periods of drying in between can cause a ratcheting effect, with rapid loss of strength during each period of rain that is not recovered during the intermediate drying periods. In addition, the results also show that the adoption of critical state soil parameters is more suitable to match the observed failure. The failure was due to a very extreme amount of rainwater infiltration in the two days before the incident, including the largest daily rainfall in 2007 of 140mm.