Dissertations / Theses on the topic 'Unsatured soil'

The prediction of moisture and contaminant transport through unsaturated soil to ground water is becoming increasingly important in the fields of hydrology, agriculture and environmental engineering. Computer aided simulation techniques enables one to conduct a series of systematic numerical experiments to analyze flow phenomenon in subsurface hydrology under various physical and chemical processes. The flow movement depends upon medium characteristics, initial and boundary conditions, which reflect, physical processes occurring below the ground. To understand the effects of physical process an efficient and accurate model is needed. Thus the model developed must be able to handle varied initial and boundary conditions. In this regard, infiltration into a very dry soil becomes a very important problem of study. Most of the earlier numerical models developed are concentrated on the development of an efficient algorithm or the modelling of a particular process which govern the flow in unsaturated or saturated-unsaturated homogeneous medium. Not much work has been done on the analysis of variably saturated flow in layered soil medium. Models to simulate unsaturated flow through dry soils, especially through layered soils with varied boundary conditions are very limited. Further, not much studies have been reported in the literature on the prediction of seepage face development and the phreatic surface movement in variably saturated media with layering. These aspects are very important in determining the flow field and the discharge from the domain. A detailed literature review covering above aspects has been made and is reported in this thesis. In the present work, two dimensional numerical models to predict the movement of wetting front in unsaturated domain and the movement of the phreatic surface in homogeneous and layered porous media under various initial and boundary conditions are developed based on finite difference and finite volume techniques. These models can handle flow in both rectangular flow domains and radial flow domains. The initial condition settings include the handling of very dry soil medium without any transformation of the governing equation, handling of infiltration and constant head conditions at the boundaries under steady state as well as transient scenarios. The models are also able to handle various soil moisture characteristics which depict the nonlinear behaviour between hydraulic conductivity, moisture content and pressure head in a soil media. A mixed form of the governing partial differential equation is used in the present study as it leads to better mass conservation. The finite difference model uses a central difference approximation for the space derivatives and an Eulerian backward difference approximation for the time derivative. The fully implicit formulation is solved iteratively using Strongly Implicit Procedure after making Picard approximation for the highly nonlinear coefficients. The process of infiltration into an initially dry soil leads to the development of a steep wetting front. As the finite volume technique is naturally an upwind method, it is expected to play a positive role in modelling such processes accurately. Hence, a finite volume model is also developed by approximating the convective part using a MUSCL approach and a fully implicit central difference method for the diffusive part of the governing equation. The models developed are validated using both experimental data and numerical solutions for problems reported in the literature. The validation problems cover a wide range of physical scenarios such as: infiltration into a very dry soil, infiltration into a dry soil column with gravity drainage, development of water table mound, steady state drainage in a sand filled wedge shaped tank with seepage face development and transient seepage face development in a rectangular domain. Five test problems are used for the validation of the models. The developed models perform very well for the test problems considered, indicating the models' capability in handling such situations. The results obtained by using the present models for simulating flow through highly unsaturated (very dry) soils show that the models perform very well when compared with models which use transformation techniques to handle such problems. The performance of the present models in comparison with the experimental data and numerical models available in the literature show the suitability of the present models in handling such situations. The present models are also used to analyse various types of unsaturated flow problems with varying initial and boundary conditions. The boundary conditions considered are no flow and /or free flow conditions along the left, right and bottom boundaries with infiltration condition along a part of the top boundary. For the various cases considered in the present study, infiltration rate varies from 5 cm/day to 50cm/day through an initially very dry soil of -15000 cm pressure head in homogeneous and layered soils. Different types of soil media considered vary from sandy loam, loam and clay with horizontal and vertical layering of these soils. A total number of 14 cases are analysed. The results are discussed in terms of pressure head variation in the flow domain along with moisture redistribution for all the cases under consideration. It is observed from these studies that the infiltration rate play an important role on the wetting front movement through layered soils depending on the type of layering and the boundary conditions considered. The soil properties of various layers affect the movement of wetting front by changing the direction of movement. Even though the wetting front movement is predominantly vertical, there is a tendency for the wetting front to move in the horizontal direction as it moves from a coarse soil to fine soil. It is also observed that the vertical layering of soils with different hydraulic conductivity helps in redirecting the flow towards the bottom boundary through the neighboring coarser layers. As finite volume method is more suitable for simulating sharp fronts, it is expected to perform better than finite difference method for simulating infiltration into very dry soils. So, a comparison is made between the performance of these two models by using the above test problems. It is observed from these studies that the performance of both the models are same except that the finite volume method takes much more CPU time than the finite difference model. Considering the type of problems tested, it is observed that for modelling unsaturated and saturated-unsaturated flows, finite difference method is better in comparison to finite volume method. It may be due to the predominant diffusive characteristics of the governing equation even while modelling flow through very dry soils. Proper estimation of the seepage height is an important aspect in finding the discharge through the porous medium. It is observed from the literature that the use of a saturated flow model in such situations can lead to an underestimation of the discharge through the porous medium. This effect is more important when dealing with small dimension problems. It is also observed that various parameters which govern the moisture movement through saturated-unsaturated regions affect proper estimation of the seepage face height and there by discharge. Various factors like effect of boundary conditions, type of soil layering, problem dimension and aspect ratio on seepage face development and the associated phreatic surface formation is studied in the present work. It is seen from the present study that the seepage face development is more in rectangular flow domain than in radial flow domain for both homogeneous and layered soils. It is also seen that the seepage face development in rectangular problems are more sensitive than radial flow problems for various factors considered. The seepage height is also influenced by the tail water level. It is seen from the present study that as the tail water level increases the seepage face reduces with no seepage face development for some of the cases studied. This influence is relatively less for radial flow problems. As the length of the domain increases the seepage height decreases. It is seen that for different cases with same horizontal dimension, as the height of the domain increases the seepage face height also increases. This phenomenon is observed for both homogeneous and layered soil medium. The influence of the aspect ratio, which is the ratio of the length to height of the domain indicate that as the aspect ratio increases the seepage height decreases. The type of the soil layering is observed to have a very strong influence on the seepage face development. The study for understanding the effect of soil layering on the development of seepage face and phreatic surface suggest that as the coarseness of the material increases, the phreatic surface become flatter and its steepness increases with the fineness of the soil. The present model is also used for studying the transient phreatic surface movement and the seepage face development. This is studied for homogeneous and layered rectangular soil medium. The present study is used to understand the effect of specific storage on the phreatic surface movement and the seepage face development. The studies indicate that the influence of specific storage on the seepage face development is insignificant in homogeneous soils with only very little effect in the early time for longer domains. It is also observed that the influence of the specific storage is significant in the case of layered soils. This effect depends on the type of layering and the problem dimension and is observed to have influence for relatively longer period. This observation suggests the importance of specific storage on transient seepage face development. When the specific storage effect is considered the drainage of the soil become faster resulting in a faster decline of the phreatic surface with time. The influence of specific storage is also studied considering the problem dimension effect. It is seen that as the aspect ratio increases, the effect of specific storage on the phreatic surface development decreases. The studies with change in the upstream boundary condition from a constant head to a no flow condition indicate that the effect of specific storage has no significant influence on the phreatic surface development for both homogeneous and layered soils.

Todo cálculo em engenharia está sujeito a incertezas, já que nenhum modelo descreve perfeitamente a realidade e está susceptível a erros de diversas espécies. No entanto, em se tratando de geotecnia, as incertezas podem ser ainda maiores, pois o material estudado – o solo – apresenta grande variabilidade. Esta dissertação tem por objetivo discutir os principais métodos de confiabilidade, e propor um procedimento prático e automático para cálculo da confiabilidade geotécnica a partir do acoplamento de um programa comercial de geotecnia – o GeoStudio – e e um programa acadêmico de confiabilidade – o StRAnD – por meio de um código em linguagem Fortran. O índice de confiabilidade e a probabilidade de falha foram estimados pelo método de primeira ordem (FORM), que mostrou bons resultados e um custo computacional bastante inferior aos métodos de simulação. O exemplo estudado nesse trabalho consistiu em um talude de solo não saturado, de forma a investigar a grande variação dos parâmetros em função da sucção. O uso do FORM nesse caso também se justificou pelo fato de as análises de fluxo terem um longo tempo de processamento. Os resultados encontrados para essa aplicação evidenciaram a importância da variabilidade dos parâmetros nas análises de confiabilidade, que podem modificar totalmente a confiabilidade do sistema. Os resultados mostraram ainda as discrepâncias que podem ocorrer em relação à análise determinística, seja em termos da superfície crítica ou do próprio diagnóstico de segurança do talude. As análises com o FORM forneceram também informações sobre a sensibilidade dos parâmetros, possibilitando reduzir o número de variáveis de forma a considerar apenas as que contribuam de forma significativa na confiabilidade, no caso, coesão, ângulo de atrito, Φb e peso específico. Ainda que os parâmetros hidráulicos não tenham apresentado grande sensibilidade neste exemplo, o aumento da quantidade de água que entra no talude, seja pelo aumento da condutividade hidráulica ou pela intensidade da chuva, mostrou uma tendência de aumento da sensibilidade desses parâmetros.
Every calculation in engineering is subject to uncertainty, since no model perfectly describes the reality and it is susceptible to errors of various kinds. However, when it comes to geotechnics, uncertainties can be even greater, because the studied material – soil – shows great variability. This paper aims to discuss the main reliability methods, and propose a practical and automatic procedure for geotechnical reliability calculation from coupling a commercial geotechnical program – the GeoStudio – and an academic reliability program – the StRAnD – using a Fortran code. The reliability index and the probability of failure were estimated by first-order method (FORM), which showed good results and much lower computational cost than the simulation methods. The sample studied in this work consisted in an unsaturated soil slope, in order to investigate the large variation of the parameters as a function of suction. The use of FORM in this case is also justified by the fact that flow analysis have a long processing time. The results for this application highlighted the importance of the parameters variability on reliability analysis, which can completely change the system reliability. The results also showed discrepancies that may occur in relation to the deterministic analysis, in terms of the critical surface or slope safety diagnosis. Analyses with FORM also provided information on the sensitivity of parameters, enabling to reduce the number of variables in order to consider only those that significantly contribute in reliability, in this case, cohesion, friction angle, Φb , and unit weight. Although the hydraulic parameters have not shown high sensitivity in this example, increasing the amount of water which enters the slope, by increasing hydraulic conductivity or the rainfall intensity, showed a tendency to increase the sensitivity of these parameters.

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.

Pipelines that are used for the transport of energy and services are very important lifelines to modem society. Though pipelines are generally buried in unsaturated soils, the design guidelines are based on the assumption that the soil is either dry or fully saturated. For certain geotechnical problems, this assumption may not be acceptable because the water meniscus formed between soil particles creates an additional normal force between them by suction, which in turn forms temporary bonds. A recent series of large-scale physical model experiments at the Pipeline Engineering Research Laboratory (PERL) of Tokyo Gas, Japan show a higher peak load under unsaturated conditions compared to dry conditions. In contrast, recent experiments performed at Cornell University (CU) show that the soil-load due to lateral pipeline movement in dry and unsaturated sands are virtually the same. Thus, the effect of partial saturation on soil loading to pipeline may be different depending on soil type, moisture content and density. The current study investigates this problem through triaxial testing and constitutive modelling of the unsaturated soils used for the experiments and finite element simulations of the experiments. The mechanical behaviour of the sands used in the physical model experiments has been investigated by conducting a series of laboratory experiments. When compacted to the same energy level, Tokyo Gas sand exhibits larger strength in unsaturated conditions than in dry conditions at low confining stress levels mainly due to the suction-induced apparent cohesion generated by the fine particles present in the sand. In contrast, for coarser Cornell sand, the suction effect is found to be small even at low confining stress level, and hence the strength in unsaturated conditions is similar to that in dry ( or fully saturated) conditions. To capture the observed behaviour of dry as well as unsaturated soils, advanced constitutive soil models were developed. For dry (or fully saturated) soils, the modified Mohr-Coulomb and Original Nor-Sand (Cheong, 2006) models were able to simulate the general behaviour including the strain softening effect. To cater for the behaviour of unsaturated soils, the saturated versions of the NorSand and the modified Mohr-Coulomb models were modified in conjunction with the generalised effective stress framework. By simulating the triaxial experimental data, it is demonstrated that the developed models can predict the realistic soil behaviour of unsaturated soils. Using the developed models, the large scale physical model experiments of pipelines subjected to lateral soil movements at PERL and CU were simulated by the explicit finite element method. Good agreement was found between the numerical models and the experiments. Further FE analyses were conducted to investigate the pipeline behaviour under lateral soil movement at conditions of different HID's, moisture contents, and relative densities. The results were synthesized to produce new normalised pipe load charts. Three dimensional finite element analysis was performed to simulate the soil-pipeline interaction under strike-slip fault movements. The finite element model was first validated by comparing the computed results to the data produced from a full scale experiment carried out at CU. The analysis was then further extended by varying the initial conditions of the sand (sand type, density, moisture content, etc.), pipe material, pipe burial depth, and pipeline-fault rupture inclination. It was found in all cases that the peak lateral loads on the pipelines subjected to strike-slip fault movements are less than or equal to the peak loads computed by the 2-D lateral movement simulations.

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This research presents the development of equipment for CRS tests with controlled suction and tests with artificially cemented unsatured soils. It was designed and constructed four apparatus at the geotechnical laboratory of the Federal University of Viçosa. The cells have an interchangeable high air entry value ceramic disc on its base. It was also designed a software for data acquisition and an apparatus for measurement of the volume of water dislocated from the sample. It was used two residual soils from Minas Gerais. Samples prepared by compaction were used in order to assure homogeneity and to avoid deviations in test results and interpretation. The tests were carried out with different levels of applied suction. Part of the samples was prepared with the addition of different amounts of Portland cement to simulate soil matrix. After cure, these samples added with cement were saturated and subjected to CRS compression tests, using the consolidation test apparatus developed. It was noticed a structure failure at low-tension levels because of the sample elaboration method. The equipment was testified as functional.
Este trabalho apresenta o desenvolvimento de equipamentos para ensaios CRS com sucção controlada e ensaios em solos não saturados cimentados artificialmente. Foram projetadas e construídas quatro células no Laboratório de Geotecnia da Universidade Federal de Viçosa. As células têm em sua base uma pedra porosa, de alto valor de entrada de ar, intercambiável. Também foram desenvolvidos um aparato de medição de volume de água deslocado do corpo-de-prova e um programa para aquisição de dados. Utilizaram-se dois solos residuais jovens de Minas Gerais. Foram usadas amostras remoldadas por compactação com o intuito de assegurar a homogeneidade e evitar desvios nos resultados dos testes e na interpretação dos dados. Os ensaios foram conduzidos com diferentes níveis de sucção. Parte das amostras foi preparada com a adição de teores de cimento Portland pra gerar uma estruturação no solo. Após o período de cura, as amostras com adição de cimento foram saturadas e submetidas ao ensaio CRS, usando os aparatos desenvolvidos. Observou-se uma quebra da estrutura com baixos níveis de tensão devido ao método adotado na elaboração das amostras. Constatou-se um bom funcionamento dos equipamentos desenvolvidos.

Ce travail s’inscrit dans le cadre du projet ANR Terredurable qui regroupe 4 thèses à vocation expérimentale et 2 thèses à vocation théorique, et peut être rangé dans la deuxième catégorie.Cette thèse est consacrée à l’étude du comportement hydro-mécanique des sols fins dans les ouvrages en terre. Ces sols se caractérisent par une saturation proche de 1 avec une présence d’air occlus apportant une forte compressibilité au fluide interstitiel. Ces sols ont un comportement qui diffère de celui des sols désaturés au-delà de l’entrée d’air et des sols parfaitement saturés.Le travail réalisé peut-être décomposé en plusieurs parties :Tout d’abord, la notion de compactage est étudiée dans le but de mieux comprendre l’importance que joue l’air de part et d’autre de l’optimum Proctor. Un travail sur la caractérisation de l’état de contrainte dans le sol à la fin du compactage et de l’évolution de sa contrainte de préconsolidation est apporté.Un modèle théorique permettant de prédire le comportement hydro-mécanique des sols proches de la saturation est présenté. Il permet de répondre à des problématiques telles que la montée des pressions interstitielles dans les noyaux de barrage pendant la construction ou encore le déconfinement de déblais après travaux de terrassement. Le modèle développé se basant sur la quantité d’air occlus au sein du fluide interstitiel a été implémenté dans un code de calcul aux différences finies et comparé aux mesures expérimentales d’essais de laboratoire et ouvrages en terre. L’instrumentation et le suivi au cours du temps du gonflement d’un déblai marneux ont été réalisés dans le cadre de cette thèse
The research presented is funded by the French National Project “TerreDurable” which is dedicated to the constitutive relations of soils in quasi-saturated conditions (close to saturation).This thesis is devoted to the study of hydro-mechanical behavior of fine soils in earthworks. These soils are closed to saturation with the presence of occluded air providing high compressibility in interstitial fluid. These soils have a behavior that differs from non-saturated soil (after air entry) and fully saturated soils.The work may be divided into several parts:• Study of compaction of fine soils and evolution of soil physical characteristics in order to characterize the initial state for a numerical modeling.• Development of a theoretical model and its implementation in a finite differences code in order to predict the evolution of pore pressure and deformation of soil near to saturation. Comparison with experimental measurements (laboratory tests and earthworks). The instrumentation and the monitoring of a marl earthwork excavation were made in the context of this thesis

Este trabalho analisa os efeitos das trajetórias de umedecimento e secagem no módulo de resiliência e cisalhamento direto quanto à resistência e deformabilidade elástica de solos compactados através de ensaios triaxiais de carga cíclica e ensaios de cisalhamento direto. O solo estudado é oriundo de jazida localizada próximo à BR116/RS, no município de Guaíba, sendo usualmente utilizado como material para execução de aterros rodoviários. As curvas de retenção do solo foram obtidas pelo método de papel filtro para solos compactados com variação de teor de umidade ótima de ±2%. Os estudos de módulo de resiliência e de resistência ao cisalhamento foram analisados nestas condições e demonstraram que o efeito do teor de umidade é significativo nas trajetórias de secagem e umedecimento. As curvas de retenção mostraram diferentes formas de acordo com a umidade de compactação e apresentaram histerese após a amostra ser submetida à trajetória de secagem. Observou-se que os solos compactados no ramo seco apresentaram valores mais elevados de módulo de resiliência e de resistência ao cisalhamento que aqueles que se encontravam no ramo úmido da curva de compactação. Uma análise do solo compactado no ramo seco e umedecido posteriormente até o ramo úmido teve comportamento semelhante aos moldados neste ramo. Por outro lado, na trajetória de secagem dos solos compactados no ramo úmido observou-se um aumento na resistência. Os modelos de desempenho para módulo de resiliência apresentaram boas correlações e para os que utilizam a sucção, observa-se um comportamento diferente com relação aos que não utilizam e com relação às constantes de cada modelo.
This paper analyzes the effects of wetting and drying paths in resilient modulus and shear strength for resistance and elastic deformability of compacted soils through triaxial cyclic load tests and direct shear tests. The soil studied is derived from BR116/RS near the Guaiba’s city, usually being used for subgrade. The retention curves of the soil were obtained by the filter paper method, with optimum moisture content varying a range of ± 2%. The studies of resilient modulus and shear strength were analyzed in these conditions and showed that the effect of moisture content is significant in the drying and wetting trajectories. The retention curves showed different forms according to the moisture content in the compaction, showed hysteresis after the specimen is subjected to the drying trajectory. It was observed that the soils compacted and tested in the dry branch had higher resilient modulus and shear strength than those compacted in the wet branch. An analysis of the soil compacted in the dry branch and subsequently dampened up to the wet branch had similar behavior to the soil molded ah this branch. On the other hand, in the trajectory of drying of the compacted soil at wet branch there is an increase in resistance. Performance models for resilient modulus showed good correlations and those using suction, observe a different behavior with respect to that use and not with respect to the constants of each model.

A thermo-elastic-plastic model for unsaturated soils has been presented based on the effective stress principle considering the thermo-mechanical and suction coupling effects. The thermo-elastic-plastic constitutive equations for stress-strain relations of the solid skeleton and changes in fluid content and entropy for unsaturated soils have been established. A plasticity model is derived from energy considerations. The model derived covers both associative and non-associative flow behaviours and the modified Cam-Clay is considered as a special case. All model coefficients are identified in terms of measurable parameters. To verify the proposed model, an experimental program has been developed. A series of controlled laboratory tests were carried out on a compacted silt sample using a triaxial equipment modified for testing unsaturated soils at elevated temperatures. Imageprocessing technique was used for measuring the volume change of the samples subjected to mechanical, thermal and hydric loading. It is shown that the effective critical state parameters M, ???? and ???? are independent of temperature and matric suction. Nevertheless, the shape of loading collapse (LC) curve was affected by temperature and suction. Furthermore, the temperature change affected the soil water characteristic curve and an increase in temperature caused a decrease in the air entry suction. The simulations from the proposed model are compared with the experimental results. The model calibration was performed to extract the model parameters from the experimental results. Good agreement between the results predicted using the proposed model and the experimental results was obtained in all cases.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 471-490). Also available in electronic version. Access restricted to campus users.

Considerable efforts have been made in recent years to develop a better understanding of the mechanical behaviour of unsaturated soils in terms of elastoplastic critical state constitutive models. These models are defined in terms of four independent stress state variables : mean net stress, deviator stress, suction and specific volume. An important feature of the models is the suggestion of the existence of a yield surface in mean net stress : deviator stress : suction space. Suction-controlled triaxial tests were performed to investigate the shape of the yield surface for unsaturated compacted speswhite kaolin with a particular stress history. The tests were conducted in a Bishop-Wesley triaxial cell with suction applied by the axis translation technique. The soil samples were instrumented with local strain gauges for measuring the sample volume change. Ten samples were tested, and in each test the location of the yield surface was fixed by isotropically consolidating the sample to a mean net stress of 400 kl'a and a suction of 100 kPa. This procedure effectively erased the one-dimensional stress history produced by the compaction process. After unloading to stress states inside the yield surface, samples were re-loaded either isotropically or by drained triaxial shearing. Re-loading stages were conducted at three different values of suction. Yield points in the re-loading stages were most easily identified from plots of specific volume against the logarithm of mean net stress (even for shear tests), whereas it was often difficult to identify a clear yield point from a plot of deviator stress against shear strain. The yield points identified from the re-reloading stages were used to define the shape of the yield surface in a stress space with axes of deviator stress, mean net stress and suction. Constant suction cross-sections of the yield surface were approximately elliptical in shape, with one axis of the ellipse coinciding with the mean net stress axis. As expected, the size of the elliptical constant suction yield curves increased with increasing suction Soil elastic indices obtained from swell-back and suction-change stages showed non-conservative behaviour, indicating that the behaviour of the soil was not truly elastic even for stress states inside the yield surface. Plastic strain increment vectors were plotted for the post-yield behaviour, and these were consistent with an associated flow rule.

The interface failure between caps and natural soil in trenches containing buried low level nuclear waste material was investigated in this study. The Casa Grande Highway Farm (CGHF) soil was used for the entire investigation. This soil is described as being a silty sand with approximately 23% by weight passing sieve No. 200. Other preliminary testing was performed on the same soil. Isotropically consolidated drained (CID) tests were performed on the laboratory compacted samples at different degree of saturation including fully saturated specimens. Suction pressure was measured in the laboratory by adopting pressure plate extractor and compared with determined effective suction in triaxial testing. A generalized failure equation, in term of strength parameters and suction pressure, was defined for all degrees of saturation. The consideration of unsaturated soil sets the current modified model apart from previous bounding surface which only allows use of fully saturated cohesive soil. The saturated material constants associated with the model are identified. These new constants are obtained from a generalized failure equation. The model was then verified by comparing predictions with other laboratory tests which are not used in the calibration. Generally a good agreement between the model and test results was found for stress-strain, stress path and volumetric strain response at different degrees of saturation. Extensive interface tests were performed in the conventional direct shear machine with some modification. Similar to trench cap soil and natural soil in the field, the test specimens were prepared at different degrees of saturation and density (compaction effort). Comparisons were made for the effects of magnitude of normal load, degree of saturation, density, compaction effort, moisture migration and dissimilar bodies density. An interface element and the modified bounding surface model and elasticity model was used in a finite element program to predict the interface response for the laboratory results and actual field problems. Material parameters related to the interface were identified and good predictions were observed for the interface behavior.

Desiccation-induced soil cracking is of significant interest in several engineering disciplines, which include geotechnical and geoenvironmental engineering, mining engineering, and agriculture engineering. The hydraulic, mechanical, thermal and other physico-chemical properties of unsaturated soils can be predominantly influenced due to cracks. Reliable information of these properties is required for the rational design and maintenance of earth structures taking account of the influence the soil-atmosphere interactions (e.g., for expansive soil slopes, earth dams, and embankments). In spite of significant research studies published in the literature on the desiccation-induced cracks during the past century, the fundamental mechanism of crack initiation and propagation of soils induced by drying and shrinkage is still elusive. For this reason, the focus of this thesis is directed towards understanding the tensile strength of unsaturated soils which is associated with soil crack initiation criterion (i.e. maximum tensile stress criterion). Tensile strength is the key property of soils for interpreting the initiation of soil cracking from a macroscopic point of view. A semi-empirical model is proposed for predicting the tensile strength of unsaturated cohesionless soils taking into account the effect of both the negative pore-water pressure in saturated pores and the air-water interfacial surface tension in unsaturated pores. The proposed model is calibrated and validated by providing comparisons between the model predictions and the experimental measurements on 10 cohesionless soils (i.e. five sandy soils and five silty soils) published in the literature. The proposed model is simple and requires only the information of Soil-Water Characteristic Curve (SWCC) and Grain Size Distribution curve (GSD), which can be obtained from conventional laboratory tests. To investigate the influence of microstructure, a practical and reliable estimation approach for predicting the evolution of the microstructural void ratio of compacted clayey soils subjected to wetting and drying paths is proposed. The microstructural evolution of 13 examined soils were investigated quantitatively using the mercury intrusion porosimetry (MIP) results. The investigated soils include four high-plasticity clays, eight low-plasticity clays and a glacial till which is a relatively coarse-grained soil with some fines. Based on this study, a novel criterion has been developed for identifying different pore populations of compacted clayey soils. The “as-compacted state line” (ACSL) was proposed to estimate the initial microstructural void ratio based on the compaction water ratio. A constitutive stress is derived to interpret and predict the volumetric deformation of compacted clay aggregates. The linear elastic constitutive model is used for predicting the microstructural void ratio of the examined compacted soils following monotonic wetting and drying paths. The developed approach (i.e. the ACSL and the linear elastic constitutive model) is validated by providing comparisons between the predicted and interpreted microstructural void ratios for all the examined soils. In addition to the matric suction and microstructure, the confining pressure also influences the tensile strength of unsaturated compacted clayey soils. The tensile strength tests on a compacted clayey soil by both the direct method (i.e. triaxial tensile test) and the indirect method (i.e. Brazilian split test) were performed. It is found that the tensile strength increases as the compaction water content decreases for the range investigated in this study, which could be explained by the variation of the inter-aggregated capillary bonding force and the change in microstructure. The increase in the confining pressure has been found to induce the change in failure mode (i.e. from pure tensile failure mode to combined tensile-shear failure mode). In spite of limitations associated with the Brazilian split test, tensile strength is widely determined using this test due to the simple procedure of specimen preparation and wide availability of test equipment in conventional laboratories. However, the Brazilian tensile strength is found to overestimate the tensile strength of compacted specimens with water content greater than the plastic limit. This is due to the considerable plastic deformation associated with the ductile failure instead of brittle failure. In summary, this thesis is devoted to providing insight into the fundamental mechanisms associated with the desiccation-induced crack initiation by quantitatively investigating the various factors that influence the tensile strength of unsaturated soils, which include the matric suction, the microstructure, and the confining pressure from theoretical studies and laboratory investigations.

The problem of cavity expansion in unsaturated soils is investigated. A unified constitutive model for unsaturated soils is presented in a critical state framework using the concepts of effective stress and bounding surface plasticity theory. Consideration is given to the effects of suction and particle crushing in the definition of the critical state. A simple isotropic elastic rule is adopted. A loading surface and bounding surface of the same shape are defined using simple and versatile functions. A limiting isotropic compression line exists, towards which the stress trajectories of all isotropic compression load paths approach. A non-associated flow rule is assumed for all soil types. Isotropic hardening/softening occurs due to changes in plastic volumetric strains as well as suction for some unsaturated soils, enabling account of the phenomenon of volumetric collapse upon wetting. Results of isotropic compression tests, oedometric compression tests and drained and undrained triaxial compression tests performed on Kurnell (quartz) sand in saturated and unsaturated states and subjected to stresses sufficient to cause particle crushing are presented and used to calibrate the model. The model is also calibrated using results reported in the literature for triaxial tests performed on saturated and unsaturated speswhite kaolin and three load paths. For both soils the model leads to a much improved fit between simulation and experiment compared to that for models based on conventional plasticity theory. The model is implemented into a cavity expansion analysis using the similarity technique, extended for application to unsaturated soils. Cylindrical and spherical cavities are considered, as are drained and undrained conditions. Cavity expansion results for the bounding surface model and conventional plasticity models are compared for saturated conditions. Substantial differences highlight the importance of adopting a model that accurately describes stress-strain behaviour. Cavity expansion results for the bounding surface model and saturated and unsaturated conditions are also compared. Substantial differences, particularly in the limit pressure, highlight the major influence of suction and the importance of accounting for this when using cavity expansion theory to interpret results of the cone penetration and pressuremeter tests.

The importance of applying unsaturated soil mechanics concepts to geotechnical engineering design has been widely recognized. Soil water characteristic curve (SWCC) and hydraulic conductivity function (HCF) are vital soil properties that govern engineering behavior of unsaturated soils. In this study, a transient water release and imbibitions method (TRIM) is used to measure the SWCC and HCF under drying and wetting states, which accommodates integrated experimental and modeling techniques. The results of saturated hydraulic conductivity tests through flexible wall method are then used as input parameters for simulating experimental data. In general, the model provides a satisfactory fit to experimental data. Soil water characteristic curves (SWCCs) and hydraulic conductivity functions (HCFs) are presented for a variety of soils that were prepared at different molding water contents and compactive efforts. The influences of dry density, molding water content, and hysteresis have been investigated. Dry density affects soil-water characteristic in terms of its air-entry value (AEV), rate of drying, and size of the hysteresis loop. The test results indicate that the SWCC and HCF obtained in terms of volumetric water content is more sensitive to the changes in dry density than molding water content. Based on cohesive soil results, some statistical relations are proposed to estimate wetting-path SWCC and HCF parameters from more easily measured drying curves. Changes in the van Genuchten's fitting parameters and residual volumetric water content are investigated for both drying and wetting conditions, with changes in the kaolin clay content.
Master of Science

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 present work is a contribution to description and understanding of the distribution and movement of water in swelling soils. In order to investigate the moisture distribution in swelling soils a detailed knowledge of volume change properties, flow characteristics and total potential of water in the soil is essential. Therefore, a possible volume change mechanism is first described by dividing the swelling soils into four categories and volume change of a swelling soil is measured under different overburden pressures. The measured and calculated (from volume change data) overburden potential components are used to check the validity of the derivation of a load factor, ∝. Moisture diffusivity in swelling soil under different overburden pressures is measured using Gardner's (1956) outflow method. Behaviour of equilibrium moisture profiles in swelling soils is theoretically explained, solving the differential equation by considering the physical variation of individual soil properties with moisture content and overburden pressure. Using the measured volume change data and moisture potentials under various overburden pressures, the behaviour of possible moisture profiles are described at equilibrium and under steady vertical flows in swelling soils. It is shown that high overburden pressures lead to soil water behaviour quite different from any previously reported.

The behavior of unsaturated soils depends heavily on material properties and soil conditions. In Geotechnical Engineering, compacted soils are frequently used as fill material, and quality control is vital to the construction process. There are few methods available to estimate the parameters associated with unsaturated soils based on field measurements, and a relationship between these factors could reduce testing time and lower construction costs. Undrained triaxial tests were performed on four clays representing a range of material properties in an effort to reach the maximum dry density, which provides the highest bearing capacity. Each clay was compacted at optimum moisture content, as well as wet and dry of optimum. Measurements were taken using the GeoGauge and shear wave velocities. An empirical approach was used to estimate the effect of a density gradient on soil suction. A relationship between the normal stress and matric suction produced a strong trend when plotted against a function of stiffness and the void ratio, which represents a density gradient. Another relationship between the GeoGauge and shear wave stiffness measurements was found, but no relationship with the material properties of the samples was observed, indicating that more in-depth research is needed to find a stronger relationship.

Innovative means and methods were tested to develop an economical, pragmatic and environmentally sustainable soil remediation process for heavy metal contaminated soils. An unsaturated-flow soil washing procedure was devised to dissolve the soil-bound toxic heavy metals; the latter were extracted by a chemical washing solution that percolated through the soil matrix. Subsequently, the leached toxic heavy metals were selectively concentrated, by a chemical precipitation process, into a solid waste. Thereby, a fraction of the spent ethylenediaminetetraacetic acid (EDTA), within the washing and rinsing leachate, was theoretically regenerated and recycle-ready.
The unsaturated-flow washing procedure was perfected by applying different treatments to a soil from a secure landfill. This soil was contaminated with Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, S and Zn. The major contaminants were Fe, Pb, Zn, S, Cu and Mn, making up 25, 1.9, 1.0, 0.4, 0.4 and 0.2%wt of the soil. The extraction responses of the contaminants and those of Al, Ca, Mg and P were established for citric acid (0.5 M) and different molarities of diammonium EDTA ((NH4)2EDTA). The DOW Chemical Company supplied the (NH4)2EDTA (i.e. VERSENE), a 1.37M industrial cleaner, which roughly costs $1.85kg-1 in bulk. The affordability of VERSENE was a pre-condition for hoping to satisfy the economical feasibility of remediating trace metal contaminated soils.
Ultimately, the developed unsaturated-flow washing procedure was tested in a pilot-scale experiment, for its ability to remediate a soil from an abandoned car battery recycling facility. The latter soil was severely contaminated with Pb (3.9%wt). Drip irrigation was used to apply (NH4) 2EDTA and water-rinsing solutions to the surface of soil heaps that rested atop an impermeable barrier, which permitted the retrieval of the leachate. A cumulative EDTA input to the soil of 10.6% wt extracted 49.4% of the total Pb content of the soil. Alternatively, readily biodegradable citric acid barely extracted 2.2% of the total Pb content of the soil, for a cumulative input of 18.1% weight of soil. Different treatments were tested for their effectiveness in concentrating the leached toxic heavy metals into a solid waste. The Pb was best precipitated with Na2S alone, as it provided the most concentrated solid toxic waste.
The environmental sustainability of remediating trace metal contaminated soils was thoroughly examined, as per the amounts of chemical entrants and toxic waste by-products, and per the post-treatment leaching of toxic levels of the remaining and potentially toxic trace metals. (Abstract shortened by UMI.)

Soil is the most widely used material in the construction of various civil infrastructure. Various types of soils are extensively used in its natural or compacted form in the construction of dams, canals, road and railway subgrades, and waste containment structures such as soil covers and liners. These infrastructure and foundation soils are exposed to the influence of environmental factors. In the permafrost and seasonally frozen regions, soils can be in different states (e.g., saturated or unsaturated, frozen or thawed, or combinations of them) due to the variations in moisture content and temperature. The soil-water characteristic curve (SWCC), which is the relationship between soil water content and suction, is used in the interpretation and prediction of unsaturated soils behavior. Similarly, the soil-freezing characteristic curve (SFCC), which is the relationship between unfrozen water content and subzero temperature, is used in the prediction and interpretation of frozen soils behavior. In this thesis, the SWCC and SFCC of two Canadian soils (i.e. Toronto silty clay (TSC) and Toronto lean clay (TLC)) were extensively investigated for better understanding the fundamental relationship between SWCC and SFCC. The soil resilient modulus (MR) is a key material property used in the rational design of pavements. Experimental investigations were undertaken to determine the MR of five Canadian soils (i.e., TSC, TLC, Kincardine lean clay (KLC), Ottawa Leda clay (OLC), and Indian Head till (IHT)), considering the influence of moisture and temperature, with the aid of an advanced triaxial testing equipment. Two simple models were proposed for estimating the MR of frozen soils, in this thesis. In addition, an artificial neural network (ANN) model was developed for estimating the MR of the five Canadian soils considering various influencing factors. The conclusions from the various studies in this thesis are succinctly summarized below. (1) Four expressions (i.e. power relationship, exponential relationship, van Genuchten equation, and Fredlund and Xing equation) that are widely used for representing the SFCC were selected for providing comparisons between the measured and fitted SFCCs for different soils. The results suggest that the exponential relationship and van Genuchten equation are suitable for sandy soils. The power relationship reasonably fits the SFCC for soils with different particle sizes, but not for saline silts. The Fredlund and Xing equation is flexible and provides good fits for all the soils. (2) The SFCC and SWCC of TSC and TLC were experimentally determined, analyzed, and compared. Many factors influence the reliable measurement of SFCC, which include sensors’ resolution and stability, sensor calibration for each soil, and thermodynamic equilibrium condition. The hysteresis of SFCC for the two soils is mainly attributed to the supercooling of pore water. The quantitative dissimilarity in the measured SFCC and SWCC may be attributed to specimen structure variations during compaction and saturation, and during freezing / thawing processes, and cracks formation due to sensors insertion. In addition, some fundamental differences may exist between the drying / wetting and freezing / thawing processes, resulting in dissimilarity. (3) Two novel models were proposed for the estimation of MR of frozen soils. The semi-empirical model extends the mechanics of unsaturated soils and employs SFCC for prediction. Several coarse- and fine-grained saturated soils were used to validate this model. The empirical hyperbolic model was proposed considering that the frozen MR versus subzero temperature relationship resembles hyperbola. This model was validated on coarse- and fine-grained soils under saturated / unsaturated conditions. The hyperbolic model has wider application since it can be used for both saturated and unsaturated frozen soils. Both the models are simple and promising. (4) The MR of five Canadian soils subjected to wetting and freezing was determined by using the GDS ELDyn triaxial testing system. A freezing system was established for controlling the desired testing temperatures within the soil specimens. The results suggest: (i) The effect of subzero temperature on the MR is significant. (ii) For TLC, KLC, OLC, and IHT, the frozen MR versus subzero temperature relationship of the saturated specimen typically has steeper slope than specimen at the optimum water content, for the temperature range from 0 to -5 °C. (iii) The effect of stress levels on the frozen MR depends on soil type, water content, and subzero temperature. Lastly, (iv) Loading frequency does not show a significant influence on the frozen MR. (5) The MR of the five Canadian soils was determined considering wetting and freeze-thaw (F-T) conditions. The results suggest: (i) The F-T cycles result in weak soil structure due to reduction in suction, particles movement, loss of cohesion, and formation of cracks / channels. (ii) The critical numbers of F-T cycles were determined as 1, 1, 2, and 1 for TLC, KLC, OLC, and IHT at the optimum water content, respectively. (iii) The percentage of reduction in MR after the critical number of F-T cycles was strongly related to the plasticity index for specimens tested at the optimum water content. (iv) The wetting process results in the decrease in suction and enlargement of soil pores. Consequently, relatively low MR values were measured at high water contents, and the effect of F-T cycles becomes insignificant. Finally, (v) The effect of stress levels on the MR was dependent on the initial water content of the specimen and soil type.

Unsaturated hydraulic conductivity was measured using four different methods. Tension permeameters were used to measure unsaturated hydraulic conductivity in the field, using a single disc method, which depends on the measurements of sorptivity, steady state flow rate, initial and final water content (White and Perroux, 1987, 1989). Also, a double disc method was used which utilizes Wooding's (1968) equation for two different disc radii at the same tension for steady state flow rates. Undisturbed and disturbed soil cores were used to measure unsaturated hydraulic conductivity in the lab, using water retention curves with van Genuchten's equations. There were no significant differences in the mean of hydraulic conductivity between single and double disc methods in all the tensions used (0, 5, 10 and 15 cm). There were significant differences between the field methods and undisturbed soil cores in zero cm tension, and disturbed soil cores in 10 and 15 cm tension. The effect of land preparation on the unsaturated hydraulic conductivity was studied using the double disc method. Tilling has significant effects on the unsaturated hydraulic conductivity at all tensions used. The spatial variation of unsaturated hydraulic conductivity and steady state flow in different tensions using the double disc method was studied. We found exponential variogram models for unsaturated hydraulic conductivity at 5, 10 and 15 cm tensions and a random model for zero cm tension. Also, exponential models were best fitted for steady state flow corresponding to pores radii of 0.03 - 0.015 cm, 0.015 - 0.010 cm and steady state flow at 10 cm tension. A Michaelis-Menton model was used for steady state flow at 5 cm and 15 cm tension. Disc permeameters were also used to add 5 cm depth of water, bromide and dye solution at 0, 5, 10 and 15 cm tensions with three replicates. A comparison was made between field data and simulated model under the same boundary and initial conditions as in the field. Results showed that the water and bromide move deeper than the prediction of the simulated model in all tensions used. The differences were larger between simulated model and field data for both water and bromide concentrations in the lower tension and smaller in the higher tension as a result of elimination of some preferential flow paths. An equation was developed for cumulative infiltration valid for both small and large time. The parameters calculated using the developed equation closely matched the measured infiltration, and fit better than a three term series similar to the Philip equation for one-dimensional flow.

Helium tracer experiments were conducted to characterize conservative tracer behavior in a wedge-shaped lysimeter containing alternating layers of unsaturated silty sand, and clay loam. Experiments were conducted with trichloroethylene and 1,1,1-trichloroethane to determine if air stripping in unsaturated soil could be characterized by mass transfer from the sorbed to the liquid to the vapor phase. Batch experiments were conducted to measure liquid--vapor mass transfer. Solid-liquid-vapor mass transfer was characterized by measuring the vapor phase re-equilibration after the air stripping experiment. The Discrete State Compartment model was used to simulate a conservative gas tracer. The results were compared to the helium tracer. Liquid-vapor, and solid-liquid-vapor mass transfer were modeled by fitting simulated data to experimental data. The conservative tracer, and mass transfer models were combined to simulate air stripping in unsaturated soil.

The objectives of this dissertation are to measure and calculate surface free energies of soil particles, to understand the mechanical behavior of unsaturated silty sand through first studying the stress-strain relationship, the effects of matric suction and pore water chemistry and second to interpret the behavior by the critical state frame work, to develop a method to predict cone tip resistance in unsaturated soils, and to present the concept of pseudo strain and dissipated pseudo strain energy. Universal Sorption Device (USD) is developed to measure surface free energies of soil particles. The test results on a soil sample shows that specific surface area increased with decreasing particle size. The components of surface free energies and the work of adhesion increased with decreasing particle size. A servo controlled triaxial testing device is developed to test 15.24 cm in height and 7.62 cm in diameter, recompacted specimens of unsaturated soil under varying matric suction and different pore chemistry. During the test, the matric suction is maintained constant. Results from the triaxial drained tests are used for validation of the constitutive models proposed by Alonso et al. (1990). Predictions from the model are in good agreement with experimental results. The critical state model for unsaturated soil is used to calculate cone tip resistance in unsaturated silty sand. The calculated cone tip resistance is used to evaluate the liquefaction potential of unsaturated soils. The results from the stress based liquefaction potential analysis reveal that even in an unsaturated condition soil is susceptible to liquefaction. By applying the pseudo strain concept, it is possible to account for the viscous resistance of water during cyclic loading. The results of undrained cyclic triaxial tests are used to calculate pseudo-strain and dissipated pseudo strain energy. The results of calculated dissipated pseudo strain energy suggest that the effect of initial matric suction is evident. On the other hand, the effect of surface tension increase or decrease due to existence of chemical on the pore water is negligible.

Unsaturated illitic soil was subjected to subfreezing temperatures to examine the effect of heat and moisture redistribution on contaminant migration.
Three series of freezing column tests and two series of cyclic freeze-thaw experiments were performed with different liquid supplies: distilled water (pH = 5.8), a municipal waste leachate (pH = 6.9) and a leachate-heavy metal solution (pH = 2.5). Temperature distribution, water content, concentration of exchangeable cations and heavy metals in pore solution were determined in frozen soil as a function of time and space. The differential scanning calorimetry technique was used to calculate the quantity of unfrozen water in the frozen specimens.
It was found that moisture intake and redistribution were closely related to the temperature gradient, the duration of freezing and the type of liquid used. The unfrozen water content, ionic concentration and temperature gradient were the controlling parameters contributing to contaminant transport in frozen soil. The distribution of exchangeable cations changed with the freezing time due to their migration and replaceability. The accumulation of heavy metals in the soil occurred as a result of cation exchange and precipitation mechanisms.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
A contaminação de solos por hidrocarbonetos é uma real preocupação ambiental em muitas partes do mundo devido a crescente dependência econômica dos derivados do petróleo, principalmente os combustíveis fósseis que estão frequentemente sujeitos a vazamentos e derramamentos acidentais. Estudos capazes de entender os mecanismos de biodegradação dos componentes da gasolina no solo não saturado se fazem necessários, pois auxiliam no processo de tomada de decisões em relação ao gerenciamento e controle da propagação em subsuperfície. No Brasil, o etanol é utilizado como aditivo oxigenado à gasolina e alguns autores sugerem para solo saturado que, por ser mais degradável, ele atrasa a degradação dos outros componentes mais tóxicos desse combustível. O trabalho anterior realizado por esse grupo de pesquisa para solo não saturado obteve conclusões semelhantes às já constatadas para solo saturado. No entanto, os mecanismos de degradação na zona não saturada ainda foram pouco estudados e compreendidos. Este estudo tem como objetivo analisar a degradação do contaminante em blocos não saturados indeformados de solo arenoso e siltoso, oriundos do município de Duque de Caxias – RJ, submetidos a um pulso de contaminante. Dois blocos, um arenoso (BA) e outro argiloso (BS), foram contaminados pela solução de dois porcento de Benzeno, quatro porcento de Tolueno em Heptano (BT); outros dois blocos, também um arenoso (EA) e outro argiloso (ES), foram submetidos à mesma solução adicionados etanol a vinte porcento (BTE). Foram realizados ensaios com a finalidade de monitorar a atividade degradadora total do meio, carbono disponível, perfil metabólico da microbiota, concentração dos contaminantes, além de medições da umidade volumétrica através do uso do Time Domain Reflectometer (TDR). A atividade microbiana inicial, antes da contaminação, apresentou valores baixos. Logo após a contaminação dos blocos, àqueles sujeitos a etanol apresentaram ausência de atividade enquanto os sujeitos apenas à mistura BT mostraram um aumento, contrariando as expectativas. As atividades microbianas oscilaram ao longo de todo o experimento o que pode indicar uma adaptação da microbiota às novas condições do meio. Com base nos resultados dos ensaios e monitoramentos realizados, podemos sugerir que o principal fator determinante para alteração da atividade foi à composição do solo. O contaminante não exerceu a influência esperada e vista nos estudos anteriores.
The soil contamination by hydrocarbons is a real environmental concern in many parts of the world due to growing economic dependence on petroleum, mostly fossil fuels are often subject to leaks and accidental spills. Studies able to understand the mechanisms of biodegradation of gasoline components in unsaturated soil are necessary because they help in making decisions regarding the management and control of the propagation process in the subsurface. In Brazil, ethanol is used as an oxygenate gasoline additive and some authors suggest that for saturated soils, being more degradable, it delays the degradation of other more toxic components of this fuel. The previous study by this research group to unsaturated soil obtained similar results to those already observed for saturated soil. However, the mechanism of degradation in the unsaturated zone have few studies. This study aims to analyze the degradation mechanisms of the contaminant in unsaturated blocks of sand and silt soil from the city of Duque de Caxias - RJ, subjected to a pulse of contaminant. Two blocks, one sandy (BA) and silty (BS), were contaminated by two percent solution of benzene, four percent toluene in heptane (BT); other two blocks, also sandy (EA) and silty (ES), underwent the same solution added to twenty percent ethanol (BTE). Analyzes were performed to monitor the overall activity of the degrading medium, available carbon, the microbiota metabolic profile, concentration of the contaminants were performed as well as measurements of the water content through the use of Time Domain Reflectometer (TDR). The initial microbial activity before the contamination, showed low values. Soon after contamination of the blocks, those subjected to ethanol showed no activity while subject to BT mixture showed an increase, contrary to expectations. Microbial activities ranged throughout the experiment which may indicate an adaptation of microbes to new environmental conditions. Based on the results of testing and monitoring conducted, we suggest that the main determinant for changing the activity factor was the composition of the soil. The contaminant did not exert the expected influence and seen in previous studies

Includes bibliography.
In this thesis tile transient flow of water, during tile drainage process in saturated-unsaturated soil profiles, was studied. Drainage experiments were performed on two different soil profiles. The first experiment undertaken was tile drainage of a vertical column of sand. This experiment was performed on two sands of differing grain size and grading. The second experiment undertaken was the drainage towards a well from a wedge of sand (cake slice) using yet a different coarse sand.

Unsaturated soils constitute a large proportion of the foundation materials supporting infrastructure throughout the world and they are subject to various loading conditions. The research into the behaviour of unsaturated soils has been ignored for many centuries; however the recent years have witnessed a surge of research activities looking into various aspects. The present research reported in this thesis places emphasis on the perfomlance of unsaturated soils under repeated loading. As part of the research, a series of monotonic and repeated load triaxial tests were perfonned on samples of kaolin clay prepared to various compaction water contents, 22%, 25%, '28% and 31% and two different compression pressures, 400kPa and 800kPa. Undrained tests were conducted in a newly developed simple triaxial cell for testing unsaturated soil under repeated loading with hydraulic loading system, hall-effect transducers for on-sample strain measurements and thennocouple psychrometer for suction measurements. Drained tests were conducted in twin-cell stress path apparatus with controlled suction by axis translation teclmique. The main findings of the research provide a remarkable insight into the influence of suction, and more imp011antly the degree of saturation, on the permanent defonnation and resilient behaviour of unsaturated compacted kaolin. At high suctions repeated loading was found to have a positive effect on the soil pelfoIl1lance. However, at low suction, repeated loading had a detrimental effect on the strength and stiffness of unsaturated soil, under both drained and undrained conditions. An important outcome of the research is the progression of permanent defoIl11ation throughout repeated loading with no asymptotic value ever being reached, particularly at loading amplitudes of more than 70% of the failure load.

Se ha llevado a cabo:A) Un estudio de las propiedades básicas del suelo no saturado (tipo limo) a escala microestructural, incluyendo esqueleto sólido, fase liquida y fase gaseosa. B) Elaboración de un modelo conceptual discontinuo de comportamiento. La geometría interna esta construida por partículas, agua retenida en forma de meniscos alrededor de los contactos y aire ocupando los restantes poros. La interfase liquido gas esta gobernada por la succión y la tensión superficial. Los meniscos tienen un efecto rigidizador del esqueleto.Se observa la posible redistribución de la humedad y del aire, quedando acoplados en definitiva los aspectos mecánicos y de flujo.C) En base a lo anterior, implementación de un modelo numérico discontinuo de ensayo de comportamiento basado en ordenador. Se ha adaptado y modificado el D.E.M. de P.A. Cundall (diferencias finitas explicitas en el tiempo), indicado en el caso que se trata, con no-linealidades geométricas. Se han desarrollado importantes algoritmos de control geométrico. D) Verificación parcial del modelo y aplicación a casos típicos en suelo no saturado, especialmente el colapso.En conjunto es una herramienta útil para su estudio y permite apreciar algunos interesantes mecanismos de actuación de la succión a escala microscópica.

Se ha llevado a cabo:

A) Un estudio de las propiedades básicas del suelo no saturado (tipo limo) a escala microestructural, incluyendo esqueleto sólido, fase liquida y fase gaseosa.

B) Elaboración de un modelo conceptual discontinuo de comportamiento. La geometría interna esta construida por partículas, agua retenida en forma de meniscos alrededor de los contactos y aire ocupando los restantes poros. La interfase liquido gas esta gobernada por la succión y la tensión superficial. Los meniscos tienen un efecto rigidizador del esqueleto.
Se observa la posible redistribución de la humedad y del aire, quedando acoplados en definitiva los aspectos mecánicos y de flujo.

C) En base a lo anterior, implementación de un modelo numérico discontinuo de ensayo de comportamiento basado en ordenador. Se ha adaptado y modificado el D.E.M. de P.A. Cundall (diferencias finitas explicitas en el tiempo), indicado en el caso que se trata, con no-linealidades geométricas. Se han desarrollado importantes algoritmos de control geométrico.

D) Verificación parcial del modelo y aplicación a casos típicos en suelo no saturado, especialmente el colapso.

En conjunto es una herramienta útil para su estudio y permite apreciar algunos interesantes mecanismos de actuación de la succión a escala microscópica.

The structures constructed on unsaturated soils are damaged by the movement of the soil underneath. The movement is basically due to the flow of moisture in and out of the soil. This change in moisture also affects the strength of the soil, thus resulting in failure of slopes of embankments constructed with these soils. Therefore, it is very important to study the diffusion properties of unsaturated soils. Study of the diffusion properties requires the determination of the diffusion coefficient (/). In this thesis improvements in the drying test, originally proposed by Mitchell (1979), have been discussed. The study also involves defining the evaporation coefficient (he) which has been ill-defined in previous research work. The flow through unsaturated soils is non-linear but due to the complexity involved it has been simplified to a linear problem. The nonlinear behavior has been studied during this research. Therefore, certain refinements have been applied in the determination of the diffusion coefficient. The laboratory procedure followed involves measuring the soil suction along the length of the sample and at different times using thermocouple psychrometers. The evaluation of the evaporation coefficient (he) has been made an integral part of the procedure. The diffusion coefficient is determined using the curve fitting procedure of Aubeny and Lytton, 2003.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A presente dissertação tem por objeto a análise teórica - comparativa, implementação computacional e avaliação da capacidade de simulação dos modelos constitutivos para solos, com ênfase nos solos não saturados. Primeiramente, são analisados os modelos básicos, clássicos e avançados formulados para solos saturados ou secos, assim como os modelos desenvolvidos para solos não saturados, incluindo também alguns modelos para solos estruturados. A seguir, e para testar a sua capacidade de modelagem, são implementadas as matrizes constitutivas de alguns dos modelos analisados para a retroanálise e previsão de comportamento de três solos residuais na condição saturada e não saturada. Como complemento da pesquisa, um dos modelos é utilizado na simulação de provas de carga com placa em solo residual pelo MEF, para os casos de saturação e umidade natural. Finalmente, são apresentadas organizadamente as conclusões gerais e particulares obtidas, assim como sugestões para futuras pesquisas no tema do presente trabalho.
The objective of this thesis is to present a critical review of the main constitutive soil models published in the literature, discussing and evaluating their abilities to simulate the mechanical behavior of geological materials under the theoretical and numerical points of view, with emphasis on unsaturated soils. Firstly, some basic, classical and advanced soil models are presented and discussed, as well as a few other recent constitutive relationships specially developed for unsaturated and structured materials. In the sequence, in order to assess the efficiency and overall performance of some selected models, the respective constitutive matrices were numerically implemented for prediction and back-analysis of the response of three residual soils, in saturated and unsaturated conditions. As a complement of this research, one of the soil models is used to simulate the results of some plate load tests on a residual soil deposit through the finite element method. Finally, the general conclusions of this work are presented and some suggestions are made to aid future research in the area of soil modeling.