Dissertations / Theses on the topic 'Soils Analysis'

The objective of this study was to assess tree species influence on forest floor fertility in a mixed forest stand using Redundancy Analysis (RDA). Eighty microsites were located in a beech-hemlock-red maple forest. Forest floor was analyzed for thirteen variables; total N, P, K, Ca and Mg, extractable Ca, Mg and K, mineralizable N (NH$ sb{4+}$), basal microbial respiration (CO$ sb2$), pH, thickness and bulk density. The influence of seven tree species was calculated as a function of tree diameter and distance from each microsite. Spatial patterns were detected by using correlograms and incorporated in a variation-partitioning model with trend surface analysis. Tree species, microtopography, and spatial structure explained 53% of the total variation in forest floor data. The fraction explained by tree species alone (16%) was studied with a RDA ordination biplot. The main source of variation in the soil data was related mainly to the opposite effects of American beech and eastern hemlock on calcium while most of the other species had a beneficial effect on soil fertility. This study showed the potential of RDA as a tool for studying the role of tree species in mixed forests.

Copies of author's previously published works inserted. Bibliography: leaves 260-299. This thesis describes the concept of organic matter turnover and various methods to measure the decay rates of organic materials in the soil. Methods are developed to separate SOM from different locations within the soil matrix. Free particulate organic matter (POM), located between or outside the soil aggregates is isolated. Occluded POM is disaggregeted by sonification. The compositional differences noted among the three components of SOM are used to describe the changes that OM undergoes during decomposition. The process is followed as organic matter enters the soil, is enveloped in aggregates and is eventually incorporated into the microbial biomass and metabolites then becoming associated with clay minerals.

An airborne multispectral video system was used to collect soil spectral data over a four-square mile region in northeastern Arizona. Six multispectral video images were digitized. Using the red and blue bands of each image, an unsupervised classification was performed. Each was referenced to a digitized U.S. Soil Conservation Service map resulting in classification precisions ranging from 0-92.4 percent. Ground radiometric measurements were made to ascertain spectral separability of the soil samples. Soil color was determined to try to relate Munsell value to classification precision. Misclassification of soil map units was unrelated to soil brightness or areal extent of each soil. Rather, features such as slope, boundary complexity, and surface condition was responsible for misclassifications seen in this study. Best classification results occurred when soil mapping units were relatively homogeneous, possessed slight changes in slope, and had a regular surface with smooth and distinct boundaries.

The behavior of porous media subjected to any arbitrary loading is a complex phenomenon due to the coupled nature of the problem. Proper understanding of this coupled behavior is essential in dealing with many of the geotechnical engineering problems. A very general three-dimensional formulation of such a coupled problem was first reported by Biot; however, a two-dimensional idealization of the theory is used here with extension to nonlinear material behavior. A finite element computer code is developed to analyze the response of coupled systems subjected to both static and dynamic excitations. The code can also be used to solve problems involving only solid media by suppressing the presence of fluid. The generalized anisotropic hardening model is implemented into the finite element procedure to characterize nonlinear material behavior throughout the realm of its deformation process. Both drained and undrained conditions are considered in order to verify the performance of the model in capturing material behavior. Three different materials are considered for this purpose. The predictions obtained using the anisotropic model for both drained and undrained condition yield satisfactory comparison with observed behavior. The finite element procedure is verified by solving several problems involving undrained, consolidation and dynamic responses of coupled system. Good agreements are found between numerical and analytical results. Further verification of the computer code and the material model is performed by solving two boundary value problems. For this purpose, a laboratory pressuremeter test subjected to quasi-static loading condition and a building foundation system subjected to rapid earthquake excitation were analyzed. The results of this research have provided an improved understanding of coupled behavior of porous media. The procedure developed here can be effectively used under a wide range of loading conditions varying from very slow quasi-static to very rapid earthquake excitations.

During a volcanic eruption, the extrusion of lava onto surfaces destroys biological activity creating virgin land surfaces. Through time this new land will be subject to soil formation and colonisation under relatively similar climatic conditions and parent materials. Soils formed from volcanic deposits present a unique opportunity to study microbial community development. Soils at different developmental stages and differing in vegetation cover were selected from four locations on the slopes of Mount Etna, Sicily. Three main research objectives were determined in order to test the hypothesis that the microbial communities from soils at later stages of development would have a greater biomass, be more diverse, be more efficient at utilising carbon sources and recover from an environmental disturbance at a greater rate. A field experiment was conducted to ascertain the long term in situ catabolic abilities of the microbial communities in each soil and to establish the effects of litter mixing on decomposition rate. Litter bags containing either Genista aetnensis (Etnean Broom), Pinus nigra (Corsican Pine) or a mixture of the two were buried at each of the sites and their decomposition monitored over a 2.5 year period. PLFA diversity, community composition and function was assessed for each of the soils. The soils were also subject to a disturbance and the recovery of key community parameters was monitored over a six month period in order to establish each soil community’s resistance and resilience to disturbance. A laboratory experiment was conducted in order to investigate functional diversity and decomposition functions of each soil community using a range of simple and complex substrates. The relationship between PLFA diversity and functional diversity was also investigated. No correlation was found between soil C and N contents, microbial biomass or soil respiration and soil developmental stage and there was no detectable difference in litter bag mass loss between the soil types. No non- additive effects were noted in mixed litters. The more developed soil had a greater PLFA diversity and PLFA biomass however the more developed soil was not more resistant or resilient to disturbance. Developed soils showed greater catabolic diversity compared with less developed soils broadly correlating with PLFA diversity. Despite increased PLFA diversity and functional diversity in the more developed soils, residue decomposition in situ was unaffected. Reduced PLFA diversity and community complexity did not result in reduced function. Soils at different developmental stages had similar catabolic responses and were able to degrade simple and complex substrates to a similar degree. Microbial diversity in soil has the potential to be very high thus resulting in a high rate of functional redundancy i.e. many species within the same community which have the same functional role. It is possible that only a few key functional groups present within the soil community contribute to the main decomposition function within the soil and were able to maintain function during perturbation. Both Etna soils had similar PLFA’s present in similar concentrations and these groups in general were maintained during disturbance. This suggests that total microbial community diversity may not be as important to community function as the presence of key functional groups.

A study is undertaken to formulate and solve the equations governing the time dependent response of gassy soils. The formulations have been implemented into a finite element program capable of analyzing stress state and flow phenomenon under a variety of boundary conditions. The validity of such a program has been verified by comparing its results with closed form solutions. This program has then been applied to simulate the processes involved in depleting oil sand reservoirs in order to give some insight into the mechanism causing fluid flow and sand production. The theory developed couples the effects of both stress and flow. It takes account of the varying permeability and compressibility of the pore fluid, and the nonlinear stress-strain behaviour of the soil. A hyperbolic model is employed to represent the soil's stress-strain characteristics and a distinction in behaviour is made between shear and tensile failures. Various schemes are proposed for transferring loads which violate the yield criterion and in ensuring that a reasonable behaviour is modelled during failure. In order to compute the change in pore pressure in gassy soils, both under undrained and transient states, the concept of a homogenized compressible phase is introduced which is used to treat a multiphase soil system as a two phase material. Such a hypothesis is found to be highly akin to the procedure normally followed in finite element analysis since it replaces the compressibility of fluid and solid phases by one phase which occupies the entire soil volume. Assuming that the gases are present only in the form of bubbles within the liquid phase, the compressibility of the fluid phase is obtained by giving due consideration to the mixture of liquid and gas phases using Boyle's law and Henry's law and taking account of the surface tension effects. Under undrained conditions the pore pressure is computed by invoking volumetric compatibility between the soil skeleton and the compressible phase. Under transient conditions, the pore pressure is calculated by using Biot's theory of consolidation and modifying it to account for a soil with an incremental stress-strain law and a compressible fluid phase. Formulations are derived to compute the change in pore pressure and effective stress as a result of changes in temperature and a methodology is proposed for implementing these effects into finite element analysis. Various numerical techniques are incorporated for increasing the accuracy, efficiency, and stability of the finite element procedure. The computer program based on these formulations is verified by comparing the computational results with known solutions for several problems. Application of the finite element program to analyze the problem of unloading a cavity in oil sand reservoir has revealed that the principal factor leading to fluid production is the compressibility attained by the pore fluid as a result of the gas evolution. It is also demonstrated that large movements develop around uncased wellbores when the internal fluid pressure is reduced below the in-situ pore pressure. The factor which governs the overall stability of the reservoir is the flow rate which is a function of the pore pressure gradient, soil strength properties, permeability, and the volume of evolved gases.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>ESCOLA TÉCNICA FEDERAL DO PARÁ<br>Este trabalho tem como objetivo apresentar um método para previsão de recalque de grupos de estacas, solicitadas axialmente em maciços de solo estratificados, através do emprego de técnicas numéricas. O método de análise utilizado é baseado em uma versão simplificada do método dos elementos de contorno, sugerida por Poulos e Davis (1968) para o caso de solo homogêneo, isotrópico e linear elástico, desenvolvida a partir das soluções de Mindlin (1936). Neste caso, a modificação proposta constou da substituição de meio estratificado por meios homogêneos equivalentes, através da utilização de procedimentos sugeridos por Poulos (1979) e Yamashita et al (1987). Os valores de recalque obtidos com os programas computacionais desenvolvidos nesta pesquisa foram comparados com resultados correspondentes obtidos pelo métodos dos elementos finitos ou publicados na literatura por diferentes autores e através de diversas metodologias. Estas comparações permitem concluir que a utilização da proposição aproximada sugerida neste trabalho fornece, sob certas condições, valores bastante satisfatórios do recalque de grupos de estacas em maciços de solo estratificados. As vantagens de utilização deste procedimento estão diretamente associadas a uma significativa simplificação na preparação dos dados para as necessárias descrições geométricas e geotécnicas do problema bem como a redução do tempo de processamento. Fatores de interação para grupos de estacas foram produzidos para alguns casos específicos de grupos em maciços de solo formados por camadas duplas.<br>This thesis presents a numerical analysis of pile groups deflections, under axial load in layered soils. The method uses a simplified version of the boundary element technique, as proposed by Poulos and Davis (1968) for a homogeneous, isotropic and linear elastic half-space, based on Mindlin s equation. In this case, the major step consisted in replacing the multi-layered system for an equivalent homogeneous half-space using the well known procedures suggested by Poulos (1979)and Yamashita et al (1987). Results of the deflection of pile groups obtained with the proposed method were compared to results obtained using finite element analysis and to results published in the technical literature obtained by several authors. It has been shown that the proposed method provides results which compare favorably with existing solution and basically presents the advantage of the simplification in handling the soil and geometrical datas necessary for the problem description. Interaction factors for groups of pile were produced for some specific cases consisting of a double layer system.<br>Este trabajo tiene como objetivo presentar un método para previsión de recalque de grupos de estacas, solicitadas axialmente en macizos de suelo extratificados, a través del empleo de técnicas numéricas. EL método de análisis utilizado tiene como base en una versión simplificada del método de los elementos de contorno, sugerida por Poulos y Davis (1968) para el caso de suelo homogéneo, isotrópico y lineal elástico, desarrollada a partir de las soluciones de Mindlin (1936). En este caso, la modificación propuesta incluye la substituición de medio extratificado por medios homogéneos equivalentes, a través de la utilización de procedimentos sugeridos por Poulos (1979) y Yamashita et al (1987). Los valores de recalque obtenidos con los programas computacionales desarrollados en esta investigación fueron comparados con resultados correspondentes obtenidos por el métodos de los elementos finitos o publicados en la literatura por diferentes autores y a través de diversas metodologías. Estas comparaciones permiten concluir que la utilización de la proposición aproximada sugerida en este trabajo brinda, bajo certas condiciones, valores bastante satisfactorios del recalque de grupos de estacas en macizos de suelo extratificados. Las ventajas de utilización de este procedimiento están directamente asociadas la una significativa simplificación en la preparación de los datos para las necesarias descripciones geométricas y geotécnicas del problema así como la reducción del tiempo de procesamiento. Fueron produzidos factores de interación para grupos de estacas para algunos casos específicos de grupos en macizos de suelo formados por estratos duplas.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>Muitos problemas da engenharia geotécnica podem ser resolvidos pela superposição de soluções singulares fundamentais das equações diferenciais governantes. Nesta dissertação, é investigado o comportamento mecânico de uma fundação flexível, em termos de tensões e distribuições de recalque, considerando algumas soluções fundamentais básicas publicadas na literatura. Estas soluções referem-se ao campo de tensões e deslocamentos gerados em um semi-espaço linearmente elástico, homogêneo e isotrópico, por uma força vertical aplicada na superfície (Problema de Boussinesq (1885)), uma força horizontal aplicada na superfície (Problema de Cerruti (1882)), uma força aplicada dentro de um semi-espaço (Problema de Mindlin (1936)) ou dentro de uma camada finita (Problema de Burmister (1945)). No caso de depósitos de solo estratificados, são poucas as soluções disponíveis, em rela ção à ocorrência comum deste tipo de solo na natureza. Uma dessas soluções foi proposta por Hisada (1995), a qual permite que a resposta da aplicação de cargas dinâmicas ou estáticas em qualquer ponto de um semi-espaço estratificado, seja numericamente avaliada. No desenvolvimento matemático, a aplicação do teorema de Green permite fazer facilmente a superposição das soluções fundamentais, transformando as integrais de área em integrais de linha ao longo dos contornos que definem a geometria de uma única fundação ou de um grupo, formado por um número qualquer de fundações superficiais. Alguns exemplos apresentados neste trabalho discutem o potencial da aplicação dessa técnica em problemas da engenharia geotécnica, com ênfase especial para aqueles da engenharia de fundações.<br>Many problems of geotechnical engineering can be solved by superposition of the fundamental singular solutions to the governing differential equations. In the dissertation, the mechanical behavior of a flexible footing is investigated, in terms of stress and settlement distributions, considered some basic fundamental solutions published in literature. These solutions refer to the stress and displacement fields in an isotropic, homogeneous, linearly elastic half-space generated by a vertical force applied on the surface (Boussinesq´s problem (1885)), a horizontal force on the surface (Cerruti´s problem (1882)), a force within the half- space (Mindlin (1936)) or within a stratum of finite thickness (Burmister´s problem (1945)). For the case of horizontal stratified soil deposits there are very few solutions available, in spite the common occurrence of this kind of soils in nature. One of such solutions has been proposed by Hisada (1995), which permits the response of a stratified half-space to dynamic or static forces, applied at any given point of the elastic medium, to be numerically computed. In the mathematical development, the application of the Green`s theorem allows the superposition of fundamental solutions to be more easily done by transforming area integrals into line integrals along the boundaries that define the geometry of either a single footing or a group formed by any number of shallow foundations. Some examples are herein presented in order to indicate the potential use of this approach to geotechnical engineering problems, in general, but with special emphasis to those of the foundation engineering.<br>Muchos problemas de la Ingeniería geotécnica pueden ser resueltos por la superposición de soluciones singulares fundamentales de las ecuaciones diferenciales governantes. En esta disertación, se investiga el comportamiento mecánico de una fundación flexible, en términos de tensiones y distribuciones de recalco, considerando algunas soluciones fundamentales básicas publicadas en la literatura. Estas soluciones se refieren al campo de tensiones y al deslizamiento generados en un semi-espacio linealmente elástico, homogéneo e isotrópico, por una fuerza vertical aplicada en la superfície (Problema de Bousinesq (1885)), una fuerza horizontal aplicada en la superfície (Problema de Cerruti (1882)), una fuerza aplicada dentro de un semi-espacio (Problema de Mindlin (1936)) o dentro de una camada finita (Problema de Burmister (1945)). En el caso de depósitos de suelo estratificados, son pocas las soluciones disponibles, comparados con la gran existencia de este tipo de suelo en la naturaleza. Una de esas soluciones fue propuesta por Hisada (1995) y permite que la respuesta de la aplicación de cargas dinámicas o estáticas en cualquier punto de un semi-espacio estratificado, sea evaluada numéricamente. En el desarrollo matemático, la aplicación del teorema de Green permite llegar facilmente a la superposición de las soluciones fundamentales, transformando las integrales de área en integrales de línea a lo largo de los contornos que definen la geometría de una única fundación o de un grupo, formado por un número cualquier de fundaciones superficiales. Algunos ejemplos que se presentan en este trabajo discuten el potencial de la aplicación de esa técnica en problemas de la Ingeniería geotécnica, con énfasis especial para aquellos de la Ingeniería de fundaciones.

This thesis has investigated the static liquefaction failure, during construction, of the Nerlerk underwater berm. This hydraulically-placed sandfill structure was designed to form part of an artificial caisson island, intended for use as a year-round exploration drilling platform in the Canadian Beaufort Sea. The aim of the investigation has been to examine how liquefaction was possible in a fill which, according to CPT data, was predominantly dilative; in particular, to study the influence, on stability, of 'pockets' of liquefiable material in the sandfill. Instead of a conventional deterministic approach, based on mean strengths, a stochastic type of approach has been necessary, in order to accurately model material heterogeneity. For this research, the double-hardening constitutive model Monot has been used, this being capable of modelling a wide range of material behaviour, from liquefiable to strongly dilative. The material parameters have been calibrated from an extensive laboratory database and expressed in terms of density via the state parameter for sands. The state parameter statistics have been derived, based on a detailed statistical evaluation of an extensive CPT database from the Tarsiut and Nerlerk island sites. These statistics were used for generating uni-variate random fields of state parameter, from which the Monot material parameters could then be backfigured, in order to model the spatial variability in the fill (i.e. heterogeneity). A number of sophisticated stochastic investigations have been performed, using an advanced two-dimensional finite element algorithm encompassing Monot. The results have shown that liquefaction of the Nerlerk berm is consistent with CPT data: i.e. it may be possible for a predominantly dilative fill to liquefy, under static loading conditions, due to the presence of semi-continuous loose zones arising from deposition-induced anisotropy. For such problems, in which material anisotropy is present, a deterministic approach is not appropriate and can be misleading, as this was shown to represent an upper bound response to the stochastic simulations.

Elastic-plastic stress·strain models are developed for initially anisotropic soils. The models are developed for both total stress (undrained) analyses and for effective stress (drained) analyses. For anlsotroplc undralned coheslve soils under monotonic loading an elastic-plastic isotropic-hardening model is developed. For complex loading conditions the model is extended using multisurface plasticity. For effective stress analyses of soils, the Cam-Clay model concepts are generalized for initially anisotropic soils. Both isotropic and anisotropic hardening are used in the model. The behavior of the models is investigated under several loading conditions and some comparisons are made with experimental triaxial data. A nonlinear three-dimensional finite element program is developed in which the models are implemented. An updated Lagrangian large displacement analysis is also included. The constitutive models developed are used to investigate the influence of initial anisotropy on the bearing capacity, deformation and pore pressure development under footings in both plane-strain and three dimensional conditions. It is found that for the range of anisotropy encountered in the field, the deformation and bearing capacity are significantly different.<br>Ph. D.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 25, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Erik Loehr. Vita. Includes bibliographical references.

The research used dendro-chemical analysis of ash tree rings and current year leaf litter to track Cd, Pb, Zn, Cu, Mn, Cr, and Sn spread and cycling from a closed garbage dump-toxic waste site. This technique allowed for determination of areal extent, contaminant levels and time period of initial contaminant contact. Only Zn, Sn, and Cu were found in elevated quantities in the xylem wood and Pb in the leaf litter. Elemental concentrations of Pb, Sn and Cd in xylem wood and leaves of ash were positively correlated. Tin was the only element to demonstrate a clear initial contact period and elemental accumulation with age. Significant levels of Cu accumulated in the heartwood while Zn revealed significant but inconsistent accumulated patterns. Expected attenuation zones associated with municipal solid waste landfill leachate dispersion were not found; thus the pathway for contaminant dispersion was likely through groundwater flow.<br>An elemental index was developed to facilitate the use of dendro-chemical analysis in periods of suppressed tree growth resulting from environmental pollution.

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.

A decade has passed since the development of the self-boring pressuremeter (SBPM). Even though the device has been recognized by the geotechnical engineering profession as having high promise for evaluating in-situ stress-strain behavior of soils, its use is limited. In large part, this is due to the fact that there are important unanswered questions about the SBPM test. One of the major issues concerns the influence of drainage in the soil as it is sheared. In clays, the test is assumed to be undrained, but there is no way to control this other than by the rate of loading and no method has been put forth heretofore to define the required rate. This dissertation addresses the drainage issue by applying a numerical model capable of simulating the pressuremeter test under variety of conditions. To develop parameters for the soil model, a comprehensive laboratory testing effort was needed. The validity of the numerical model and the soil parameters is established by comparing it to SBPM tests performed in the field. The numerical model uses the finite element method in a special code capable of handling large strains, consolidation effects, and nonlinear soil behavior. Particular attention is addressed to the issue of pore pressure development and its dissipation. Relative influences of important soil parameters such as the permeability are checked against various rates of loading in the SBPM test. The results demonstrate that drainage likely occurs in most cases using conventional test procedures, and that this, in turn, leads to an error in interpretation of SBPM data. Based on the findings in the analyses, a procedure is proposed which should lead to a more rational method of performing the SBPM test where nearly undrained conditions are desired.<br>Ph. D.

Two objectives are achieved in this thesis: (1) to develop a new method to measure the pH-dependent net surface charge of soils and (2) to determine if, by a combination of the surface charge evaluated by potentiometric titration and ion adsorption, we can separate the permanent charge, generated by the isomorphous substitution, from the variable charge. First, a laboratory procedure, using backtitration, was developed for the measurement of the pH-dependent net surface charge. This method was tested on ten soil horizons from Gleysols and Podzols. It appears that the pH-dependent net surface charge, measured by this technique, shows good agreement with that measured by ion adsorption. It is also possible, with this method, to identify some plateaus and inflection points in the backtitration curve associated with protonation/deprotonation reactions of specific soil components. Secondly, it was demonstrated that it is possible to increase the surface charge of montmorillonite with Al-oxide coatings under specific conditions.

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.<br>Master of Science

Frost heave describes the phenomenon whereby soil freezing causes upwards surface motion due to the action of capillary suction imbibing water from the unfrozen region below. The expansion of water on freezing is a small part of the overall surface heave and it is the flow of water towards the freezing front which is largely responsible for the uplift. In this thesis, we analyse a model of frost heave due to Miller (1972, 1978) which is referred to as `secondary frost heave'. Secondary frost heave is characterised by the existence of a `partially frozen zone', underlying the frozen soil, in which ice and water coexist in the pore space. In the first part of the thesis we follow earlier work of Fowler, Krantz and Noon where we show that the Miller model for incompressible soils can be dramatically simplified. The second part of the thesis then uses this simplification procedure to develop simplified models for saline and compressible soils. In the latter case, the development of the theory leads to the consideration of non-equilibrium soil consolidation theory and the formation of segregated massive ice within permafrost. The final part of the thesis extends the simplified Miller model to the analysis of differential frost heave and the formation of patterned ground (e.g. earth hummocks and stone circles). We show that an instability mechanism exists which provides a plausible theory for the formation of these types of patterned ground.

The thesis focuses on the experimental and theoretical aspects of the process of cracking in drying soils. The results and conclusions were drawn from an exhaustive experimental campaign characterised by innovative multidisciplinary aspects incorporating Fracture Mechanics and classical Soil mechanics, aided with image analysis techniques. A detailed study of the previous works on the topic showed the absence of large scale fully monitored laboratory tests, while the existing studies were performed on already cracked soil, rather than focusing on the process of cracking. Also, the absence of a multidisciplinary approach was strongly felt. The soil used in the present work is a Barcelona silty clay, extensively studied previously for its Thermo-Hydro-Mechanical (THM) behaviour. Tensile strength and fracture toughness are two important fracture parameters that were not characterized previously and which were determined for the soil used in the investigation. The effect of moisture content on tensile strength and fracture toughness was established. The variation of tensile strength with the degree of saturation was theoretically explored considering the concept of unsaturated cohesion, while the concepts of activation energy and rate process theory were used to explain the relation between the fracture toughness and moisture content. Preliminary desiccation tests were conducted to gain basic knowledge of the cracking behaviour of Barcelona soil. Further experiments were conducted in a controlled laboratory environment with rectangular holding trays of similar geometry with five different surface areas. Crack initiation, temporal evolution of cracks resulting in the final crack pattern, meeting and bifurcation of cracks resulting in intersections, etc. were studied in detail. One of the objectives of the desiccation tests with similar geometry was to check the applicability of fracture mechanics. The results of the experiments showed existence of size-effect in soil cracking, thus justifying the use of fracture mechanics as a framework to model crack propagation. A novel equipment capable of simulating the different combinations of climatic conditions with monitoring by sensors and a digital camera was designed and constructed. This enivironmental chamber can hold large specimens up to 80 cm in diameter and 20 cm thick. The results from experiments carried out with the environmental chamber have provided new knowledge about the process and mechanisms of desiccation cracking. Some observations made during the experiments prompted more detailed experiments on some aspects of crack formation. The morphology of cracks, fissures, and the presence of spiral and ripple-like cracks on the bottom surface demanded to explore a different theoretical point of view into the mechanism of cracking in soils. The possibility of using a theory based on either classical or unsaturated soil mechanics is critically examined, with emphasis on the importance of surrounding ambient conditions and seasonal variations. Finally, detailed macro-morphology analysis of the crack patterns was performed. A theory was developed based on the morphology of crack patterns to explain the crack formation as a result of successive domain divisions or hierarchical nature of crack formation. To test the proposed theory, temporal evolution of cracks and crack pattern were studied in detail, showing the existence of hierarchy very clearly. An attempt has been made to explore a new way of analysing the cracking in soils as a process in transition from a disordered (at crack initiation) to a deterministic behaviour (at the end of drying resulting in a complex pattern). Finally, the possible mechanisms for the formation of cracks at the bottom of the specimens were examined, with emphasis on curling and synaeresis processes.<br>La tesis se centra en los aspectos teóricos y experimentales del proceso de agrietamiento de suelos por desecación. Los resultados y las conclusiones fueron extraídos de una exhaustiva campaña de experimentación caracterizada por su aspecto multidisciplinario, incorporando las bases de la mecánica de fractura y la mecánica del suelo con la ayuda de técnicas de análisis de imagen. Un estudio detallado de los trabajos anteriores sobre el tema puso de manifiesto la ausencia de experimentos a gran escala monitorizados en el laboratorio. Los estudios existentes se han realizado sobre suelos agrietados en lugar de centrarse en suelos en proceso de agrietamiento. Es remarcable, además, la ausencia de un enfoque multidisciplinario. El suelo utilizado en el presente trabajo es una arcilla limosa de Barcelona, ampliamente estudiada por su comportamiento Termo-Hidro-Mecánico (THM). Se recopilaron las características geológicas y geotécnicas reportadas en anteriores tesis doctorales y se determinaron dos nuevos importantes parámetros de fractura tales como la resistencia a tracción y la tenacidad de fractura del suelo estudiado. Fueron utilizados equipos específicos para cada parámetro. Se estableció el efecto del contenido de humedad en el suelo sobre la resistencia a tracción y tenacidad de fractura. Se estudió de forma teórica la variación de la resistencia a tracción con el grado de saturación, teniendo en cuenta el concepto de cohesión no saturada. Los conceptos de energía de activación y teoría de tasa de proceso se utilizaron para explicar la relación entre la tenacidad de fractura y el contenido de humedad. Para conocer el comportamiento del suelo estudiado en cuanto a desecación y agrietamiento se realizaron unos ensayos preliminares. Adicionalmente, se realizó otra serie de experimentos con bandejas de geometría similar pero con diferente superficie, estudiando con precisión detalles como la iniciación y la evolución temporal de las grietas, sus intersecciones y el patrón final de agrietamiento. En general los resultados de los ensayos de desecación confirmaron los datos conocidos, excepto algunas observaciones que no correspondían a ningún resultado de estudios previos publicados. Uno de los objetivos de los ensayos de desecación con geometrías similares fue el de estudiar la aplicabilidad de la teoría de Mecánica de Fractura. Los experimentos demostraron la existencia del efecto del tamaño en el agrietamiento del suelo, justificando el uso de la mecánica de fractura como marco teórico de referencia para modelar el proceso de propagación de las fisuras en suelos. Se diseñó y construyó un nuevo equipo especial para el estudio del fenómeno del agrietamiento por desecación, la cámara ambiental, capaz de simular las diferentes combinaciones de condiciones climáticas con control por sensores y una cámara fotográfica digital integrada. En ella se pudieron estudiar muestras de gran tamaño, hasta 80 cm de diámetro y 20 cm de espesor. Algunas observaciones llevadas a cabo durante los experimentos mostraron la necesidad de realizar estudios ms detallados y de cambiar el punto de vista teórico del mecanismo de agrietamiento de suelos. Especialmente, teniendo en cuenta la presencia de grietas en forma de espiral en la superficie inferior de la muestra. La posibilidad de utilizar teorías basadas tanto en la mecánica de suelos clásica como en la no saturada fue examinada desde un punto de vista crítico, con énfasis en la importancia de las condiciones ambientales y las variaciones estacionales. Por último, se llevó a cabo un estudio sobre la macro-morfología detallada del patrón de agrietamiento. Una teoría basada en la morfología de las grietas fue desarrollada para explicar la formación de las grietas como resultado de las sucesivas divisiones de áreas integrales o de la naturaleza jerárquica de la formación de grietas. Para probar la nueva teoría, se estudió la evolución temporal de las grietas y el patrón de fisuras en detalle y los resultados mostraron la existencia de una jerarquía clara. Se realizó un intento de explorar una nueva forma de enfocar el agrietamiento de suelos como una conducta desordenada o determinista. Finalmente, los posibles mecanismos para la formación de grietas en la parte inferior de la muestra fueron examinados, dando importancia a los fenómenos de deformación por flexión y sinéresis.<br>La tesis es centra en els aspectes teòrics i experimentals del procés d’esquerdament en sòls per dessecació. Els resultats i les conclusions varen ser extretes d’una exhaustiva campanya d’experimentació caracteritzada pel seu aspecte multidisciplinari, incorporant les bases de la mecànica de fractura i la mecànica del sòl amb l’ajuda de tècniques d’anàlisis d’imatge. Un estudi detallat dels treballs anteriors sobre el tema va posar de manifest l’absència d’experiments a gran escala monitoritzats al laboratori. Els estudis existents s’han realitzat sobre sols esquerdats en comptes de centrar-se en sòls en procés d’esquerdament. És remarcable, a més, l’absència d’un enfocament multidisciplinar. El sòl utilitzat en el present treball és una argila llimosa de Barcelona, àmpliament estudiada pel seu comportament Termo-Hidro-Mecànic (THM). Es varen recopilar les característiques geològiques i geotècniques descrites en anteriors treballs i es varen determinar dos nous importants paràmetres de fractura tals com la resistència a tracció i la tenacitat de fractura del sòl estudiat. Van ser necessaris equips específics per a cada un dels paràmetres. Es va establir l’efecte del contingut d’humitat del sòl sobre la resistència a tracció i la tenacitat de fractura. Es va explorar de forma teòrica la variació de la resistència a tracció amb el grau de saturació, tenint en compte el concepte de cohesió no saturada. Els conceptes d’energia d’activació i la teoria de velocitat dels processos es varen utilitzar per a explicar la relació entre la tenacitat de fractura i el contingut d’humitat. Per a conèixer el comportament del sòl estudiat en quan a dessecació i esquerdament es varen realitzar uns assaigs preliminars. Addicionalment, es varen realitzar una altra sèrie d’experiments amb safates de geometria similar però amb diferents superfícies, estudiant amb precisió detalls com l’inici i l’evolució temporal de les esquerdes, llurs interseccions i el patró final d’esquerdament. En general els resultats dels assaigs de dessecació varen confirmar les dades conegudes, exceptuant algunes observacions que no corresponien a cap resultat d’estudis previs publicats. Un dels objectius dels assaigs de dessecació amb geometries similars va ser el d’estudiar l’aplicabilitat de la teoria de mecànica de fractura. Els experiments varen demostrar l’existència del efecte del tamany en l’esquerdament de sòls, justificant l’ús de la teoria de la mecànica de fractura com a marc de referència per a un model teòric de propagació d’esquerdes en sòls. Es va dissenyar i construir un nou equip especial per a l’estudi del fenomen d’esquerdament per dessecació, la cambra ambiental, capaç de simular diferents combinacions de condicions climàtiques amb control per sensors i una càmera digital integrada. Amb ella es varen poder estudiar mostres de gran tamany, fins a 80 cm de diàmetre i 20 cm d’espessor. Algunes observacions dutes a terme durant els experiments varen mostrar la necessitat de realitzar estudis més detallats i de canviar el punt de vista teòric del mecanisme de d’esquerdament en sòls. Especialment, tenint en compte la presència d’esquerdes en forma d’espiral a la superfície inferior de la mostra. La possibilitat d’utilitzar teories basades tant en la mecànica de sòls clàssica com en la no saturada va ser examinada des d’un punt de vista crític, emfatitzant la importància de les condicions ambientals i les variacions estacionals. Per últim, es va estudiar la macro-morfologia detallada del patró d’esquerdament. Una teoria basada en la morfologia de les esquerdes va ser desenvolupada per explicar la formació de les esquerdes com a resultat de les successives divisions d’àrees integrals o de la naturalesa jeràrquica de la formació d’esquerdes. Per a provar la nova teoria, es va estudiar l’evolució temporal de les esquerdes i el patró d’esquerdament en detall i les resultats varen mostrar l’existència d’una jerarquia clara. Es va realitzar un intent d’explorar una nova manera d’observar l’esquerdament de sòls com una conducta desordenada o determinista. Finalment, els possibles mecanismes per a la formació d’esquerdes a la part inferior de la mostra varen ser examinats, donant importància als fenòmens de deformació per flexió i la sinèresi.

The understanding of soil behavior is the foundation where the geotechnical engineering is built on. Experimentation is essential to improve this comprehension, and then to be able to translate it into models, theories, or laws. In a proper scientific method, experimentation is present in all phases of model development from conception to validation. This Thesis focuses on laboratory experimentation. The experiments are interesting because they are an abstraction of reality, focusing on the objective of the investigation. The main advantage of laboratory experiments is the high reproducibility, which, together with the control of the initial and contour conditions, enables to analyze the effects of different variables on the soil behavior. This Thesis focuses on the development and improvement of methodologies and techniques to provide more and better information from the laboratory experiments in a massive and non-invasive way. The developed methodologies are based on the analysis of sequential images of experiments which are able to provide the spatial distribution through the domain of the analyzed variables. The first technique presented and validated is the Particle Image Velocimetry - Numerical Particle (PIV-NP). This is a post-process to enhance the image correlation methods (PIV). The method is able to transform the instantaneous displacements measured by PIV between two consecutive images on fixed points in the space into accumulated displacements and strains on points (Numerical Particles) which represent portions of the moving soil analyzed. The method is especially suitable for the analysis of large displacements and strains experiments and combines the advantages of Eulerian and Lagrangian scheme. The validation of the method is done by means of synthetic examples and laboratory tests. For application on unsaturated soils, the Thesis presents a methodology to measure the degree of saturation (Sr) using Short-Wave InfraRed images (SWIR). The methodology is based on the relatively high absorbance of light by water in specific wavelengths of the SWIR spectrum (1400 -1550 nm and 1900 – 2000 nm) respect to the solid particles of soils. The methodology is created to be applied in a sequence of images to analyze the spatial distribution of degree of saturation and its evolution in time. The average Pixel Intensity is measured in a grid of points in each image. The Pixel Intensity is normalized and translated into its correspondent degree of saturation using the calibration curve previously calibrated. Both techniques, PIV-NP and Sr measurements from SWIR image, are combined into an integrated methodology. The result provides the position, velocity, acceleration, strains, and degree of saturation in time of the analyzed moving soil discretized into numerical particles. This allows to compare and correlate directly all the variables. The methodology offers different options to display the results: surface (2D), line (1D), and particle (0D). The information that provides each display dimension is complementary and useful for a complete understanding of the soil behavior. Finally, the integrated methodology is also applied combining the PIV-NP with a more mature technique to measure the degree of saturation in transparent soils developed in Canada. The study of the dry footprints on the seashore is the chosen case to show the capability of the combined techniques on the analysis of soil behavior. The three different options of results display are crucial to understanding the correlation between the degree of saturation and the velocity of failure. The methodology and techniques developed can be used in any geotechnical laboratory and conform a base to extend the volume of data that can be obtained from the experiments, but especially enhancing the utility of the information deduced from the data.<br>La comprensió del comportament del sòl és el fonament sobre el qual es construeix l'enginyeria geotècnica. L'experimentació és essencial per millorar aquesta comprensió, i després poder traduir-la en models, teories o lleis. En un mètode científic adequat, l'experimentació està present en totes les fases del desenvolupament del model, des de la concepció fins a la validació. Aquesta tesi se centra en l'experimentació de laboratori. Els experiments són interessants perquè són una abstracció de la realitat, centrant-se en l'objectiu de la investigació. El principal avantatge dels experiments de laboratori és l'alta reproductibilitat, que, juntament amb el control de les condicions inicials i de contorn, permet analitzar els efectes de diferents variables en el comportament del sòl. Aquesta tesi es centra en el desenvolupament i la millora de metodologies i tècniques per a proporcionar més i millor informació dels experiments de laboratori de forma massiva i no invasiva. Les metodologies desenvolupades es basen en l'anàlisi d'imatges seqüencials d'experiments que poden proporcionar la distribució espacial de les variables analitzades en tot el domini. La primera tècnica presentada i validada és el Particle Image Velocimetry - Numerical Particle (PIV-NP). Aquest és un post-procés per millorar els mètodes de correlació d'imatges (PIV). El mètode és capaç de transformar els desplaçaments instantanis mesurats per PIV entre dues imatges consecutives en punts fixos en l'espai en desplaçaments acumulats i deformacions en punts (Partícules Numèriques) que representen parts del sòl analitzat en moviment. El mètode és especialment adequat per a l'anàlisi de grans desplaçaments i experiments de deformació, combina els avantatges dels esquemes eulerià i lagrangià. La validació del mètode es realitza mitjançant casos sintètics i experiments de laboratori. Per aplicacions en sòls no saturats, la Tesi presenta una tècnica per mesurar el grau de saturació (Sr) utilitzant imatges infraroges d'ona curta (SWIR). La metodologia es basa en l'alta absorció de la llum per l'aigua comparativament a les partícules sòlides dels sòls, en longituds d'ona específiques de l'espectre SWIR (1400-1550 nm i 1900-2000 nm). La tècnica es crea per ser aplicada a una seqüència d'imatges, per analitzar la distribució espacial del grau de saturació i la seva evolució en el temps. La intensitat de píxel mitjana es mesura en una quadrícula de punts en cada imatge. La intensitat del píxel es normalitza i es tradueix en la seva corresponent grau de saturació utilitzant la corba de calibratge prèviament calibrada. Les dues tècniques, els mesuraments PIV-NP i Sr a partir d'imatges SWIR, es combinen en una metodologia integrada. El resultat proporciona l'evolució en el temps de la posició, la velocitat, l'acceleració, les deformacions i el grau de saturació del sòl analitzat en moviment, discretitzat en partícules numèriques. Això permet comparar i correlacionar directament totes les variables. La metodologia ofereix diferents opcions per mostrar els resultats: superfície (2D), línia (1D) i partícula (0D). La informació que proporciona cada dimensió de visualització és complementària i útil per a una comprensió completa del comportament del sòl. Finalment, la metodologia integrada també s'aplica combinant el PIV-NP amb una tècnica més madura desenvolupada al Canadà per mesurar el grau de saturació en sòls transparents. L'estudi de les petjades seques a la vora de la platja és el cas triat per mostrar la capacitat de les tècniques combinades en l'anàlisi del comportament del sòl. Les tres diferents opcions de visualització de resultats són crucials per comprendre la correlació entre el grau de saturació i la velocitat de trencament. La metodologia i les tècniques desenvolupades es poden utilitzar en qualsevol laboratori geotècnic i conformen una base per ampliar el volum de dades que es poden obtenir dels experiments, però especialment millorant la utilitat de la informació deduïda de les dades<br>La comprensión del comportamiento del suelo es el cimiento sobre el cual se construye la ingeniería geotécnica. La experimentación es esencial para mejorar esta comprensión, y luego poder traducirla en modelos, teorías o leyes. En un método científico adecuado, la experimentación está presente en todas las fases del desarrollo del modelo, desde la concepción hasta la validación. La experimentación comprende dos tipos diferentes de datos: datos de campo y de laboratorio. Ambos enfoques son esenciales y complementarios, considerando sus debilidades y fortalezas. Esta tesis se centra en la experimentación de laboratorio. Los experimentos son interesantes porque son una abstracción de la realidad, centrándose en el objetivo de la investigación. La principal ventaja de los experimentos de laboratorio es la alta reproducibilidad, que, junto con el control de las condiciones iniciales y de contorno, permite analizar los efectos de diferentes variables en el comportamiento del suelo. Esta tesis se centra en el desarrollo y la mejora de metodologías y técnicas para proporcionar más y mejor información de los experimentos de laboratorio de forma masiva y no invasiva. Las metodologías desarrolladas se basan en el análisis de imágenes secuenciales de experimentos que pueden proporcionar la distribución espacial a través del dominio de las variables analizadas. La primera técnica presentada y validada es la Particle Image Velocimetry – Numerical Particle (PIV-NP). Este es un postproceso para mejorar los métodos de correlación de imágenes (PIV). El método es capaz de transformar los desplazamientos instantáneos medidos por PIV entre dos imágenes consecutivas en puntos fijos en el espacio en desplazamientos acumulados y deformaciones en puntos (Partículas Numéricas) que representan partes del suelo analizado en movimiento. El método es especialmente adecuado para el análisis de grandes desplazamientos y experimentos de deformación, combina las ventajas del esquema euleriano y lagrangiano. La validación del método se realiza mediante ejemplos sintéticos y pruebas de laboratorio. viii Para aplicaciones en suelos no saturados, la Tesis presenta una metodología para medir el grado de saturación (Sr) utilizando imágenes infrarrojas de onda corta (SWIR). La metodología se basa en la alta absorción de la luz por el agua con respecto a las partículas sólidas de los suelos, en longitudes de onda específicas del espectro SWIR (1400-1550 nm y 1900-2000 nm). La metodología se crea para ser aplicada en una secuencia de imágenes, para analizar la distribución espacial del grado de saturación y su evolución en el tiempo. La intensidad de píxel promedio se mide en una cuadrícula de puntos en cada imagen. La intensidad del píxel se normaliza y se traduce en su correspondiente grado de saturación utilizando la curva de calibración previamente calibrada. Ambas técnicas, las mediciones PIV-NP y Sr a partir de imágenes SWIR, se combinan en una metodología integrada. El resultado proporciona la evolución en el tiempo de la posición, la velocidad, la aceleración, las deformaciones y el grado de saturación del suelo analizado en movimiento, discretizado en partículas numéricas. Esto permite comparar y correlacionar directamente todas las variables. La metodología ofrece diferentes opciones para mostrar los resultados: superficie (2D), línea (1D) y partícula (0D). La información que proporciona cada dimensión de visualización es complementaria y útil para una comprensión completa del comportamiento del suelo. Finalmente, la metodología integrada también se aplica combinando el PIV-NP con una técnica más madura desarrollada en Canadá para medir el grado de saturación en suelos transparentes. El estudio de las pisadas secas en la orilla de la playa es el caso elegido para mostrar la capacidad de las técnicas combinadas en el análisis del comportamiento del suelo. Las tres opciones diferentes de visualización de resultados son cruciales para comprender la correlación entre el grado de saturación y la velocidad de rotura. La metodología y las técnicas desarrolladas se pueden utilizar en cualquier laboratorio geotécnico y conforman una base para ampliar el volumen de datos que se pueden obtener de los experimentos, pero especialmente mejorando la utilidad de la información deducida de los datos

Little is known about the original properties of soils in the East. Eight virgin soils and associated southern Appalachian hardwood vegetation were studied in western North Carolina. The study sites ranged in elevation from 720 to 1200 m on steep slopes. Overall these soils are quite deep and highly weathered due to high rainfall (>200 cm) and soluble feldspathic parent material. Organic matter contents of the surface·horizons were quite high (4.5 - 16 %), and they contained moderate to strong crumb structure. All but one soil contained cambic subsurface horizons and were either Typic Haplumbrepts or Umbric Dystrochrepts. The majority of soils in the watershed are formed in colluvium, but significant amounts of residual soils occur on sideslopes, and appear to be quite stable. The present day landforms appear to be the result of periglacial activity. North-facing soils were higher in whole soil clay, organic matter, and A horizon exchangeable cations than south-facing soils. Cation exchange capacity in these soils is almost totally dependent on organic matter content, and the mineral fraction is relatively inert. All soils were in the oxidic mineralogy class. Bibbsite was common throughout all soils and hydroxy-interlayered vermiculite (HIV) is the dominant clay-sized phyllosilicate in surface horizons. Kaolinite was low in all soils, but was more abundant on south-facing slopes. The silt fractions and sand fractions contained significant quantities of weathered 2:1-type minerals The vegetation varied from mixed-mesophytic cove hardwoods on north-facing slopes to mixed oak-hickory and oak-pine on south-facing slopes. Many trees in coves exceed 1.3 m in diameter and 50 m in height. Total litter production averaged 3494 kg/ha, and the litter layers were typified by thin leaf (L), and well developed fermentation (F) and humus (H) layers. Cations and P are concentrated in the litter layers and immediate surface soil, while N is mixed deep into the profile. Due to their oxidic mineralogy, low CEC, decreasing clay content with depth, and concentration of cations and P in litter and standing biomass these soils highly resemble tropical Oxisols.<br>Ph. D.

As testing stiff soils in the laboratory often leads to information which is not consistent with field performance, research was undertaken to determine in situ the soil properties. Among the devices which generated interest is the self-boring pressuremeter (SBPM). In this research, two stiff soils of the Commonwealth of Virginia were tested: A residual soil found in Blacksburg and a very stiff, non-fissured, and sensitive clay, of marine origin, known as the Miocene clay of the downtown Richmond area. Testing the residual soil of Blacksburg with the SBPM led to the following new operational approaches: (1) a systematic use of a steel-sheath known as "Chinese lantern" to protect the membrane of the probe, (2) the development of a loading frame providing adequate reaction when self-boring in stiff soils, (3) the development of a new calibration unit for the SBPM which allows to calibrate the probe under conditions more like those encountered in stiff soils and, (4) the development of a high capacity computerized data acquisition system. Testing the residual soil also allowed to establish a sound database for this soil. In the Miocene clay, the laboratory test results indicate that conventional sampling technique which consists in pushing Shelby tubes disturbs significantly the soil and leads to scattered test results. In contrast, tests performed on samples taken from high-quality block samples indicate consistent behavior patterns. SBPM test results in the Miocene clay indicate that the clay exhibits high lateral stresses. They also indicate the existence of an anisotropic state of lateral stress which can be explained from the regional topography. The soil parameters interpreted from the SBPM test results in the Miocene clay compare well with the soil parameters determined in the laboratory on the block samples.<br>Ph. D.<br>incomplete_metadata

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.

Switchgrass (Panicum virgatum) has been widely investigated because of its notable properties as an alternative pasture grass and as an important biofuel source. The goal of this study was to determine soil suitability for Switchgrass in Mississippi. A linear weighted additive model was developed to predict site suitability. Multicriteria analysis and Sensitivity analysis were utilized to optimize the model. The model was fit using seven years of field data associated with soils characteristics collected from NRCS-USDA. The best model was selected by correlating estimated biomass yield with each models soils-based output for Switchgrass suitability. Pearsons r (correlation coefficient) was the criteria used to establish the best soil suitability model. Coefficients associated with the best model were implemented within a Geographic Information System (GIS) to create a map of relative soil suitability for Switchgrass in Mississippi. A Geodatabase associated with soil parameters was constructed and is available for future GIS use.

Soil contamination from petroleum spills is a frequent environmental problem in the world. It is obvious that petroleum exploration has contributed immensely to the economic growth of Nigeria, but over the last few decades, the Niger Delta of Nigeria has suffered grave human health risk and ecosystem degradation resulting from oil spillages, petroleum products leakages and other involuntary effluent discharges from oil exploration activities. This research seeks to develop and optimize GC-FID methods for the analysis of Petroleum hydrocarbons. Crude oil spillage contamination of soil from the Niger Delta was investigated 3 months after a crude oil-pipeline spillage. 47 Soil samples (300-500g) were collected at several points in the South-South Niger Delta. Control samples were taken from four unaffected sites within the vicinity of spillage with similar soil characteristics. Samples were collected at depths of 0-15 cm, 15-30 cm and 30-60 cm. The soil samples were prepared for analysis using solvent extraction methods, passed through column of sodium sulphate and Florisil® to aid in column performance, remove moisture and gross impurities. Samples were analysed using gas chromatography with a flame ionisation detector. Penetration and migration of C10-C26 and C26-C34 hydrocarbons through the soil layers were assessed by cluster analysis to determine the spatial distribution, penetration and chemical similarity of these compounds over the contaminated area. This information is a useful guide for bioremediation purpose. It was found that total petroleum hydrocarbon concentrations varied from 9-289 mgkg-1 topsoil, 8-318 mgkg-1 subsoil and 7-163 mgkg-1 at the greatest depth measured.The results show elevated levels of total hydrocarbon contents when compared with the reference sites. Drastic steps should be taken to carefully monitor and remediate the environment. Bioremediation with plants and micro-organisms is endorsed.

Materiales arcillosos rígidos, que se encuentran en la zona de transición entre suelos duros y rocas blandas, están siendo considerados actualmente en varios países como la roca huésped para el almacenamiento geológico profundo de residuos nucleares de alta actividad y larga vida. Esta posibilidad a derivado en la construcción de laboratorios de investigación subterráneos (LIS), excavados en estos materiales arcillosos rígidos, para estudiar su comportamiento bajo condiciones reales de trabajo. Entre los diferentes aspectos estudiados en los LIS, el comportamiento hidromecánico de la roca huésped es el más relevante para la presente investigación. Observaciones in situ han revelado que las excavaciones inducen daño alrededor de los túneles, en la forma de redes de fracturas, contenidas dentro de una zona llamada la zona de daño de la excavación (ZDE). La ZDE se ha identificado como una de las principales causas afectando el comportamiento de las excavaciones. En este contexto, el principal objetivo de la presente investigación es la simulación numérica del comportamiento hidromecánico de excavaciones experimentales llevadas a cabo en el LIS Meuse/Haute-Marne (Francia). Para lograrlo, se desarrolló un modelo constitutivo para caracterizar la roca huésped. El modelado de estos materiales es una tarea desafiante. Estos materiales exhiben características más propias de los suelos como considerables deformaciones plásticas, dependencia con la velocidad de carga, y creep, aunque también muestran características más típicas de las rocas como un considerable reblandecimiento y deformaciones plásticas localizadas. Además, debido a su origen sedimentario, también exhiben anisotropía en propiedades como su rigidez, resistencia, y permeabilidad. Se prestó especial atención a la reproducción de la ZDE y, por lo tanto, a la simulación objetiva de deformaciones localizadas; se empleó un enfoque no local para la regularización del continuo, el cual evita la dependencia con la malla empleada. Los resultados obtenidos proporcionan importantes conclusiones respecto al comportamiento hidromecánico de estos materiales arcillosos rígidos, e indican los principales aspectos que afectan la respuesta de las excavaciones subterráneas. En particular, se demuestra la importancia de la ZDE.<br>Stiff clayey materials, lying in the transition between hard soils and weak rocks, are being currently considered in several countries as possible host medium for deep geological disposal of high active and long-lived nuclear waste. This possibility has led to the construction of underground research laboratories (URL), excavated in these indurated clayey materials, to study their behaviour under real working conditions. Among the very different topics addressed in the URLs, the hydromechanical behaviour of the host rock is the one that most concerns the present research. In situ observations have revealed that excavation operations induce damage around the galleries, in the form of fracture networks, contained within a zone called excavation damaged zone (EDZ). The EDZ has been identified as one of the main aspects affecting the behaviour of the excavations. In this context, the main objective of the present study is the numerical simulation of the hydromechanical behaviour of experimental excavations performed at the Meuse/Haute-Marne URL (France). For this purpose, a constitutive model has been developed to characterise the host formation. The modelling of these stiff argillaceous materials is a quite challenging task. They exhibit soil-like features like considerable plastic strains, rate-dependency, and creep, although they also show characteristics more typical of a rock such as significant softening and localised deformations. In addition, due to their sedimentary origin, they often exhibit anisotropy in properties like stiffness, strength, and permeability. Special attention has been paid to the reproduction of the EDZ and, therefore, to the objective simulation of localised deformations; a nonlocal approach has been employed for the regularisation of the continuum, avoiding the dependence on the employed mesh. The obtained results provide relevant insights into the hydromechanical behaviour of these stiff clayey materials, and they indicate the main aspects affecting the response of the underground excavations. In particular, the relevance of the EDZ has been demonstrated.

Recent interest in "greener" geothermal heating and cooling systems as well as developments in the quality assurance of cast-in-place concrete foundations has heightened the need for properly assessing thermal properties of soils. Therein, the ability of a soil to diffuse or absorb heat is dependent on the surrounding conditions (e.g. mineralogy, saturation, density, and insitu temperature). Prior to this work, the primary thermal properties (conductivity and heat capacity) had no correlation to commonly used soil exploration methods and therefore formed the focus of this thesis. Algorithms were developed in a spreadsheet platform that correlated input boring log information to thermal properties using known relationships between density, saturation, and thermal properties as well as more commonly used strength parameters from boring logs. Limited lab tests were conducted to become better acquainted with ASTM standards with the goal of proposing equipment for future development. Finally, sample thermal integrity profiles from cast-in-place foundations were used to demonstrate the usefulness of the developed algorithms. These examples highlighted both the strengths and weaknesses of present boring log data quality leaving room for and/or necessitating engineering judgment.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>No presente trabalho realizou-se a implementação de um programa de análise de estabilidade de encostas incluindo aspectos não convencionais tais como ruptura progressiva, anisotropia de resistência e considerações de não saturação do solo. O método generalizado das cunhas de Sarma 79 foi utilizado para consideração destes aspectos, tomando-o como base para o desenvolvimento desta nova ferramenta analítica, aplicável ao estudo da estabilidade de encostas em solos residuais não saturados. A simulação dos efeitos da ruptura progressiva foi realizada a partir do trabalho desenvolvido por Huaman (1991), na Puc-Rio. O programa desenvolvido apresenta rotinas de geração automática da superfície de ruptura e do conjunto das inclinações críticas das interfaces das cunhas, além de diversas formas de consideração das poropressões, incluindo a possibilidade de ocorrência da sucção. Além do critério de ruptura de Mohr-Coulomb foi implementado um modelo anisotrópico de resistência que permite a representação de uma anisotropia que pode existir, mesmo em solos homogêneos, de acordo com a metodologia apresentada por Bicalho (1991). Os resultados obtidos através das rotinas implementadas foram comparados com os existentes na literatura, resultantes de análises realizadas por outros métodos de análise, comprovando desta forma, a eficiência do programa desenvolvido neste trabalho.<br>Here a computer software including non traditional issues as progressive failure, anisotropy and unsaturated soil for general slope stability analysis is implemented.The generalized method Sarma 79 was the base to consider these non-traditional issues on this new tool for the slope stability study of unsaturated residual soils.The progressive failure simulation effects were carried out following Huaman (1991) in his work at PUC-Rio, and aspects of anisotropy followed the work by Bicalho (1991). The computer program has subroutines that automatically construct the critical failure surfaces of any shape and the critical inclination of wedges set besides several ways of considering water pressures and suction ocurring. The strength anisotropy model allows to consider micro structural anisotropy within the context of the Mohr- Coulomb failure criterion. The results from the developed tool were compared with ones published on the current literature.

Cette thèse présente une analyse probabiliste de fondations superficielles reposant sur un sol variable spatialement et soumises à un chargement statique ou dynamique (sismique). Dans la première partie de cette thèse, le cas d'un chargement statique a été considéré. Dans cette partie, seule la variabilité spatiale du sol a été examinée et les propriétés du sol ont été modélisées par des champs aléatoires. Dans la littérature, la méthode de simulation de Monte-Carlo (MCS comme Monte Carlo Simulation) est généralement utilisée. Dans cette thèse, la méthodologie de développement par chaos polynomial creux (SPCE comme Sparse Polynomial Chaos Expansion) est employée. Cette méthode vise à remplacer le modèle élément fini/différence finie par un méta-modèle. Cela conduit (dans le cas présent des problèmes stochastiques à grande dimension) à une réduction significative du nombre d'appels du modèle déterministe. En outre, une utilisation combinée du SPCE et de l'analyse de sensibilité globale GSA (dénommée SPCE/GSA) est proposée pour réduire encore une fois le coût de l'analyse probabiliste pour les problèmes faisant intervenir un modèle déterministe coûteux. Dans la deuxième partie de cette thèse, le chargement sismique a été considéré dans l'analyse probabiliste. Dans cette partie, la variabilité spatiale du sol et/ou la variabilité temporelle du chargement sismique ont été prises en compte. Dans ce cas, le chargement sismique a été modélisé par un processus aléatoire. Les résultats numériques ont montré l'effet significatif de la variabilité temporelle du signal sismique dans l'analyse probabiliste<br>The aim of this thesis is to study the performance of shallow foundations resting on spatially varying soils and subjected to a static or a dynamic (seismic) loading using probabilistic approaches. In the first part of this thesis, a static loading was considered in the probabilistic analysis. In this part, only the soil spatial variability was considered and the soil parameters were modelled by random fields. In such cases, Monte Carlo Simulation (MCS) methodology is generally used in literature. In this thesis, the Sparse Polynomial Chaos Expansion (SPCE) methodology was employed. This methodology aims at replacing the finite element/finite difference deterministic model by a meta-model. This leads (in the present case of highly dimensional stochastic problems) to a significant reduction in the number of calls of the deterministic model with respect to the crude MCS methodology. Moreover, an efficient combined use of the SPCE methodology and the Global Sensitivity Analysis (GSA) was proposed. The aim is to reduce once again the probabilistic computation time for problems with expensive deterministic models. In the second part of this thesis, a seismic loading was considered. In this part, the soil spatial variability and/or the time variability of the earthquake Ground-Motion (GM) were considered. In this case, the earthquake GM was modelled by a random process. Both cases of a free field and a Soil-Structure Interaction (SSI) problem were investigated. The numerical results have shown the significant effect of the time variability of the earthquake GM in the probabilistic analysis

Due to rapid urban developments and limited land in urban areas, it becomes necessary to construct underground transport infrastructure at much greater depths and quite often in poor ground congested with building structures and utilities. Deep excavation inevitably alter the ground conditions and induced ground deformations. This may cause damage to adjacent building structures and utilities. Therefore, understanding and being able to predict the performance of deep excavations to minimise movements induced damages is an important issue and a challenge to geotechnical engineers. Traditionally, deep excavation analysis makes use of conventional soil mechanics and simple structural mechanics along with appropriate modifications according to field observed behaviours. Empirical data are normally used by designers to estimate excavations induced ground movements. Such approaches have been successful in the past especially for shallow excavations at only a few meters. Because of space constraints, present day excavation sometimes has to be made vertically, and the retention system used is constructed at close proximity to existing building structures and utilities. Under such circumstances, a conventional design approach has limited use and an advanced numerical method must be employed.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>Griffith School of Engineering<br>Science, Environment, Engineering and Technology<br>Full Text