Dissertations / Theses on the topic 'Soil analysis'

5 pp.
Soil testing is comprised of four steps: Collection of a representative soil sample, laboratory analyses of the soil sample, interpretation of analytical results, and management recommendations based on interpreted analytical results.

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.

Thesis (Ph. D.)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xix, 246 p.; also includes graphics. Includes abstract and vita. Advisor: William E. Wolfe, Dept. of Civil Engineering. Includes bibliographical references (p. 137-142).

This thesis provides a detailed study of slope reinforcement in soil slopes using soil nails, anchors and other mechanical stabilization methods. The major emphasis is on the use of soil nails in slopes formed with mostly residual soils. A comparative study has been performed reviewing the different methods of slope stability analysis, and the shear strength parameters used in stability analyses, the soil models used in numerical analyses, residual soil profiles and their detailed engineering properties used in previous studies and various computer software which are currently in use. An important conclusion concerning previous studies on slope stabilisation is that although some of them have focused on residual soils and specifically on soil nailed walls based in residual soil, there is not enough evidence available to show the effect of different parameters including soil strength, soil stiffness and also modelling assumptions on the result of stability analysis. Therefore, following a detailed discussion of the employed procedure for selection of geotechnical properties of residual soil, selection of modelling parameters for nailed wall, soil model and geotechnical software that were used, numerical models were built to perform a parametric study for stability assessment of nailed walls in residual soils.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Grifffith School of Engineering
Science, Environment, Engineering and Technology
Full Text

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.

Thesis (Ph.D.)--University of Missouri-Columbia, 2006.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (April 26, 2007) Vita. Includes bibliographical references.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A utilização de inclusões passivas para reforços de solos, técnica comumente conhecida como solo grampeado, vem tendo aceitação crescente junto a profissionais de engenharia civil, em especial no Rio de Janeiro. Esta técnica, porém, carece de um estudo detalhado sobre a influência dos parâmetros relevantes na deformabilidade de maciços grampeados. Os grampos são inclusões rígidas, instaladas suborizontalmente, sem tensão ou trecho livre, pois as barras de aço são introduzidas em um furo preenchido com calda de cimento. As forças axiais nos grampos são obtidas através da descompressão lateral causada pela escavação do solo. O grampeamento é feito na massa de solo à medida que escavações são executadas em etapas, obtendo se uma zona reforçada que atua como suporte da massa de solo posterior, sem reforço. A face frontal da escavação é usualmente protegida por concreto projetado, sem funções estruturais. Esta pesquisa objetiva avaliar a influência dos diversos parâmetros geotécnicos e geométricos no comportamento tensão deformação de escavações grampeadas com face vertical e superfície do terreno horizontal. A análise paramétrica foi realizada pelo FLAC (Fast Lagrangian Analysis of Continua) que é um programa computacional baseado no método das diferenças finitas. Este programa simula o comportamento bidimensional de estruturas reforçadas, constituídas de solo e ou rocha, que possam ser submetidos a escoamento plástico quando o limite de resistência é atingido. Os resultados mostram que o módulo de Young (E) e a coesão do solo (c) são de grande relevância para o projeto de estruturas grampeadas. Adicionalmente, as análises indicam que a resistência ao cisalhamento na interface solo-grampo (qs) é também um parâmetro importante, particularmente nos casos com grampos de comprimento (L) inferior a 80 por cento da profundidade de escavação (H) (L/H < 0,80). Recomenda-se que o valor de qs seja determinado diretamente a partir de ensaios de arrancamento no campo. No que se refere à inclinação dos grampos, os resultados mostram que não há diferenças significativas nos deslocamentos do maciço reforçado para lambda menor ou igual a 10 graus. Estes resultados são particularmente interessantes do ponto de vista de execução, pois inclinações da ordem de 10 graus facilitam os procedimentos de injeção no campo. Os resultados obtidos nesta pesquisa indicam o uso de comprimentos de grampos maiores que 70 por cento da altura de escavação (L/H > 0,70) na técnica do solo grampeado.
The use of passive inclusion for soil reinforcements, technique usually known as soil nailing, has been gaining growing acceptance within civil engineering professionals,especially in Rio de Janeiro. However this technique lacks a more detailed study on the elevant parameters influencing the deformability of soil nailed masses. The nails are rigid inclusions, sub horizontally positioned, without tension or free space between the nail and the surrounding soil mass. The axial forces on the nails are developed due to lateral decompression caused by soil excavation. As the excavation stages proceed, the nails are successively being installed, producing a reinforced zone, which acts as a support for the soil mass. The frontal face of the excavation is usually protected by shotcrete, and has no structural functions. This research aims at evaluating the influence of the various geotechnical and geometric parameters on the stress strain behavior of nailed excavations, with vertical face and horizontal soil surface. The parametric analysis was performed using FLAC (Fast Lagrangian Analysis of Continua), which is a computer program based on the finite difference method. This program simulates bi dimensional behavior of reinforced structures of soils and or rocks,which may be submitted to plastic flow when the strength limit is reached. The results show that the Youngs modulus (E) and soil cohesion (c ) have a very significant influence on the displacement of a soil nailing structure. The analysis also indicates that the mobilized shear strength at the soil nail interface (qs) is also an important parameter, particularly for nail lengths (L) smaller than 0,80 of the excavation height (H) (L/H < 0,80). It is therefore recommended that qs be directly determined by pullout in situ tests. Regarding nail inclination the results suggests no significant influence on the reinforced soil mass displacement for alpha less or equal than 10 degrees. These results are particularly relevant for engineering practice, because a 10 degrees inclination facilitates grouting injections in the field. The results in this research indicates the use of nail lengths (L) greater than 0,70 of the excavation height (H) (L/H greater than 0,70) in soil nailing technique.

COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
A utilização de materiais geossintéticos como reforço em obras geotécnicas vem crescendo bastante nas últimas décadas. A geogrelha, cuja função primária é o reforço de solos, é um entre os diversos tipos de geossintéticos, que vêm sendo utilizados. Diversas são as formas de interação da geogrelha com o solo em um maciço reforçado e o entendimento dos mecanismos que se desenvolvem nestas interações é essencial, pois só a partir daí pode-se obter parâmetros confiáveis para projeto. Pesquisas vêm sendo realizadas por diversos autores, mas muitos aspectos ainda devem ser estudados para que se tenha uma melhor compreensão do comportamento de solos reforçados com geogrelhas. A utilização de uma ferramenta numérica pode ser uma alternativa para que consigamos dar um passo adiante no entendimento da técnica de solo reforçado. Então, modelagens numéricas de ensaios triaxiais e de cisalhamento direto em solos reforçados e não reforçados foram realizadas com a utilização do programa Plaxis. Foram analisadas a influência do reforço no aumento da rigidez e resistência do solo e a resistência de interface solo-reforço. Para calibrar o programa e validar as análises numéricas, foram realizadas retro-análises dos ensaios realizados por Sieira (2003), onde se definiram aspectos importantes para modelar os ensaios, tal como, a melhor forma de impor as condições de contorno. Os resultados obtidos nas análises numéricas dos ensaios triaxiais sugerem que o programa Plaxis permite de forma razoável a reprodução dos ensaios reforçados, sendo possível prever o ganho de resistência do solo com a inclusão do reforço. Uma análise alternativa, onde se aplica um incremento de tensão confinante representativo da influência do reforço, foi também realizada. As análises numéricas dos ensaios de cisalhamento direto em solo arenoso não reforçado permitiram verificar a rotação do eixo das direções das tensões principais quando é aplicado carregamento cisalhante e a presença de uma zona central de cisalhamento (zona de cisalhamento). A resistência de interface sologeogrelha não foi bem reproduzida, indicando que o Plaxis não permite este tipo de avaliação. Quando os reforços encontravam-se inclinados, verificou-se a maior eficiência do reforço rígido e fazendo ângulo de 60º com a superfície de ruptura.
The use of geosynthetic materials as reinforcement in geotechnical engineering works is significantly increasing over the past decades. Geogrid, whose primary functions is reinforcing the soil mass, is one of the geosynthetics that has been used. In a reinforced soil structure, there are different types of interaction between soil and geogrid. To be possible to obtain reliable design parameters is essential to know the mobilized mechanisms in the interaction. This situation has been investigated by many researchers, but there are still many aspects to be better understood about geogrid reinforced soil behavior. In this research, numerical tools have been used to improve our knowledge about reinforced soil techniques. Numerical modeling of triaxial and direct shear tests on reinforced and non reinforced soils were carried out using software Plaxis. It was verified the resistance and stiffness increase of the soil due to geogrid inclusion and the interface soil-reinforcement resistance parameters. To calibrate the software and to validate the numerical analyses, back-analyses of the tests carried out by Sieira (2003) were done. These results helped to define important aspects to the tests modeling such as geometry and tests boundary conditions. The numerical analyses of the triaxial tests suggest that the software Plaxis reasonably allow an adequate reproduction of the reinforced soil tests. It was possible to foresee the increase of soil resistance because of reinforcement inclusion. In addition, an alternative analysis, where one applies a confining stress that reproduces the reinforcement influence, it was done. Numerical analyses of non reinforced direct shear tests had numerically evidenced the rotation of the axis of the principal stresses directions and the presence of a central zone of shear (shear zone). The soil- geogrid interface resistance was not well reproduced, indicating that Plaxis does not allow this type of evaluation. To inclined reinforcement relative to failure plane, it was verified the maximum gain of resistance is achieved with inclined reinforcement at 60º and when rigid geogrids are used.

Thesis (Ph. D.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains viii, 91 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 63-64).

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.

Cut-to-length logging is a mechanized method for delimbing trees and cutting them to length. It is a two-machine operation; taken care by a harvester and a forwarder. The forwarder can cause soil rutting, soil compaction and other detrimental after effects. Therefore it has become vital to protect the forest floor from destructive effects of heavy machines. This initiated the study to delve more into the interaction between the loaded forwarder wheel and the soil. Various WES based rut depth models has been compared to validate its effectiveness in predicting the rut depths. New models have been developed to estimate the rut depth produced by the multipass effect of wheels. Models that could predict the contact pressure between the tire and soil as well as the tire soil contact area has been studied. Various relations to determine the mobility parameters have also been studied. The ones that are suitable to predict mobility parameters have been identified. Roots play a major role in reinforcing the soil and protecting them. This extra reinforcement provided by roots has been taken into account in the thesis work. Lab test with pine tree roots have been carried out to determine the extra reinforcement supplied. Models that are capable of predicting the reinforcement effects due to roots have also been looked into. An initial step towards connecting WES and Bekker models have been done; available models correlating both WES and Bekker models have been analysed and finally a set of relations connecting both have been derived. The effect of slip on sinkage has been studied with the help of both WES and Bekker based models. Multibody simulation software MSC Adams has been used to simulate the forwarder model to determine its suitability for rut depth prediction. Adams has been employed to study the effect of tire inflation pressure and velocity on rut depth.
Kortvirkesmetoden är en mekaniserad för skogsavverkning. Det är en två-maskinsprocess, som utförs av en skördare och en skotare. Skotaren kan orsaka skador på marken, som exempelvis spårbildning och markpackning. Det har blivit allt viktigare att skydda skogen från de marskador orsakade av tunga maskiner. Detta är en initiell studie av samspelet mellan mark och hjul på en lastad skotare. Olika WES-baserade spårdjupsmodeller har jämförts för att värdera deras förmåga att prediktera spårdjupen. Nya modeller har också utvecklats för att uppskatta relationen mellan spårdjup och flera hjulpassager. Modeller som kan prediktera kontakttrycket mellan däcket och marken, samt däckets markkontaktarea har studerats. Olika relationer för att bestämma mobilitetsparametrarna har också studerats. Rötter spelar en viktig roll för att öka markens bärighet och att skydda den. Rötternas effekt på markens bärighet har behandlats i examensarbetet. Labbtester med tallrötter har genomförts för att bestämma deras armeringseffekt. Modeller som kan användas för att prediktera rötternas effekter har också studerats. Ett första steg för att kunna kombinera WES- och Bekker-modeller har utförts, tillgängliga modeller som korrelerar WES- och Bekker-modeller har behandlats och en uppsättning relationer som relaterar de båda modellerna har härletts. Effekten av halka i samband med nedsjunkning har studerats med hjälp av både WES- och Bekkerbaserade modeller. Dynamiksimuleringsprogramet MSC Adams har använts för att simulera skotarmodellen för att bestämma dess lämplighet för spårdjupsförutsägelse. Adams har använts för att studera vilken effekt olika däcktryck och hastighet har på spårdjupet.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Na atualidade, devido à necessidade de realizar obras de engenharia de grande porte em ambiente urbano, o engenheiro defronta-se muitas vezes com o desafio de executar escavações profundas, as quais devem ser projetadas para serem estáveis e limitar deformações a níveis aceitáveis. Uma escavação profunda estável é aquela cujas paredes não colapsam e o seu fundo não experimenta levantamento descontrolado. Deformações do solo podem afetar construções vizinhas, vias urbanas e outras instalações públicas, com consequências que dependem tanto da magnitude quanto do padrão do movimento do solo ao redor da escavação. A previsão do comportamento de uma escavação profunda envolve análises tanto de estabilidade quanto de deformação. Análises de estabilidade podem em geral ser feitas através de métodos de equilíbrio limite, mas as análises de deformações, por outro lado, são mais difíceis de serem previstas, necessitando do auxilio de métodos numéricos. Nesta dissertação, o comportamento de escavações profundas é investigado numericamente pelo método de elementos finitos, com especial atenção à ocorrência de deformações, para cuja previsão requer-se a utilização de modelos constitutivos que representem muitos dos aspectos de comportamento de solos reais.
At the present, due to the need for engineering works of large scale in urban environment, the engineer is confronted often with the challenge of performing deep excavations, which should be designed to be stable and with acceptable levels of deformations. A stable deep excavation is that, whose walls do not collapse and its base does not experience uncontrolled heave. Soil deformations can affect neighboring buildings, urban roads and other public facilities, with consequences that depend on both the magnitude and the pattern of the movement of the soil around the excavation. The prediction of the behavior of a deep excavation therefore involves stability analysis as well as deformation analysis. Stability analysis can generally be made through limit equilibrium methods, but deformation analyses are more difficult to predict, requiring the assistance of numerical methods. In this dissertation the behavior of deep excavations is numerically investigated by the finite element method, with special attention to the occurrence of deformations, for this prediction requires the use of constitutive models that represent many aspects of behavior of real soils.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
BOLSA NOTA 10
A presente tese tem como objetivo avaliar a interação trovão-solo no que toca a ocorrência de trovões e suas características microssísmicas, apontando a influência de vibrações induzidas para a redução do fator de segurança em uma análise (pseudo-estática) de estabilidade de encostas. Considerando a abordagem inédita, foi efetuado um levantamento teórico com o intuito de apresentar as principais características dos relâmpagos e suas correlações com o solo. Como material, foi utilizado um solo coluvionar, composto principalmente de quartzo, feldspato e biotita. O referido foi caracterizado através de métodos padrão (complementados com o uso da microtomografia 3D), e a retenção e disponibilidade de água foram reveladas. Foi efetuado um monitoramento de campo de longo prazo para avaliar a correlação entre os dados climáticos (incluindo incidência de raios) e o potencial hídrico dos solos. Por fim, foi utilizado uma estação para monitoramento sismográfico para captar as vibrações induzidas por trovões nos solos. Os resultados mostram 39 ocorrências de raios próximos ao local de monitoramento de campo. O monitoramento sísmico mostrou que os trovões causam sinais microssísmicos compostos por acelerações de pico do solo até 0,02 m/s ao quadrado. Em conclusão, para fins geotécnicos, o trovão é um assunto que pode ser avaliado à luz de um carregamento sísmico.
The present thesis aims to evaluate thunder-soil interaction verifying the influence of its induced vibrations to the reduction of the factor of safety in a pseudo-static slope stability analysis. In order to carry out this research, considering the unpublished approach, a theoretical survey was made in order to present the main characteristics of the lightning and its correlations with the soil. As a material, a colluvial soil, mainly composed of quartz, feldspar and biotite was characterized by standard methods (supplemented with the use of 3D microtomography) in order to reveal its mineral composition, structural arrangement and water retention. After field and laboratory calibration of the water potential and volumetric moisture sensors, a long-term field monitoring was performed to evaluate the correlation between climatic data (including lightning incidence) and soil water potential. Finally, a seismographic monitoring station was used to capture the vibrations induced by thunder in the soils. The results depicted 39 lightning events near the field monitoring site. However, no rapid variation of water potential was revealed during thunderstorm days. Seismic monitoring showed that thunder caused micro-seismic signals composed of ground peak accelerations up to 0.02 m/s squared. In conclusion, for geotechnical purposes, thunder is a subject that can be evaluated in the light of pseudostatic loads. However, further researches are required to verify the vibrations of larger magnitudes, induced by rays that occur at smaller distances of the seismic monitoring point.

This paper discusses a modular open source electronic soil analysis system embedded in a remote vehicle designed for use on a colonizationeffort Mars rover. The embedded system consists of a soil extraction drill sheath, a temperature and moisture array sensor sheath, a sample return bay specialized for RamanFluorescence spectrometry, and an Ethernet bridge radio for communication, all controlled through several microcontroller boards. A Windowsbased graphical engagement application provides real time control. A Linuxbased scripting application provides postprocessing, graphing, and statistical analysis. All software and electrical hardware has been made opensource for the public to build upon.

The slope failure is a dangerous phenomenon for natural or man-made slopes. Such failures can be assess by different numerical or limit state methods. However, other new techniques can be utilized to simulate the slope failures in more effective ways in order to save the construction costs. In this research, a model based on particle image velocimetry is developed to analyze the behavior of slope stability. This method provide real time safety factors and instantaneous velocities of slope movement which are applicable for shallow slope failure studies.

The objective of this study was to use pedological evidence in conjunction with Geographic Information Systems, and soil physical and chemical analyses as means to better understand the agricultural landscape surrounding the ancient Maya city of Uci. Specifically, the query of this thesis is to determine whether there is an association between settlement density and soil resources, and what relationship if any there is between the ancient sacbe of Uci and its surrounding agricultural potential. Stable carbon isotope analysis of the humin fraction of the soil organic matter was conducted on several profiles from karst depressions known as rejolladas near the site center, and from a select number of sufficiently deep profiles along and surrounding the ancient sacbe, and from beneath ancient structures. A strong C isotopic signature of ancient C4 crops was found in a limited number of profiles while a majority of the profiles showed no evidence, or little to inconclusive evidence due to a mixture of C3 and C4 plants in the natural landscape. A majority of the soils surrounding Uci are shallow to extremely shallow and many profiles sampled and studied did not allow for C isotopic analysis. Isotopic evidence along with other soil chemical and physical characteristics suggests that settlement density was linked to soil resources, specifically in the case of the rejolladas proximity to the Uci site center. However, it does not appear that the construction and location of the sacbe was linked to its surrounding soil resources or agricultural potential even though ancient maize crops may have been cultivated sporadically close to the sacbe and nearby structures. The soil resources of Uci are not conducive to the production of large maize crops and the ancient Maya of this area likely utilized maize along with alternative crops, arboriculture, wild game and trade to sustain its population.

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.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003.
Includes bibliographical references (leaves 201-205). Also available in electronic version. Access restricted to campus users.

Tillage operations in farming often require high traction forces applied by tractor wheels. These interact with topsoil via a stress system along the contact surface, this interaction resulting in soil and tyre deformation. Topsoil is subject to normal and tangential stresses at the contact surface. The tangential stress rises sharply with increasing traction force and may cause topsoil among tyre lugs to fail, with the consequent formation of a strengthless layer strongly exposed to erosion and an underlying layer where shear deformations contribute to the alteration of soil structure functionalities. This work aimed to investigate mechanical conditions along the soil-tyre contact surface which lead to topsoil damage. These conditions are analysed in the light of simulations with a soil-tyre interaction model and discussed on the basis of results of specific experimental tests. A semi-empirical model of interaction between the soil and a pneumatic wheel was adapted to simulate the traction performance of mechanical front-wheel drive MFWD vehicles, taking into account the load transfer effect, the multi-pass effect, and the theoretical speed ratio between the front and the rear axles. This model was employed to simulate (i) the traction performance of tractors in terms of drawbar pull, motion resistance due to soil compaction, traction coefficient and traction efficiency as a function of slip, wheel load and tyre inflation pressure; (ii) soil stress paths along the contact surface with tyres; and (iii) the risk of soil failure corresponding to a defined slip level. Several traction tests were performed on four agricultural soils of different texture (clay, clay loam, silty loam, and loamy sand). Four tractors of wide ranging power (40.4 kW, 65 kW, 110 kW, and 123 kW) and weight (25.3 kN, 40 kN, 66.7 kN, and 68 kN) were used. Tractor configurations were varied by changing tyre inflation pressure and tractor weight, and by using dual tyres. Slip normally ranged between 0% and 35%, only in some cases higher values, up to 58%, were reached. The shearing effect on the topsoil due to slip of tractor tyres was investigated on the silty loam agricultural field by measuring longitudinal topsoil displacements along the driving corridors during traction tests. A system of strips orthogonal to the tractor track was spray-painted on the soil surface to enable easy visualisation of the topsoil displacements. The changes in soil hydraulic properties owing to deformation caused by the passage of the 40 kN tractor, both in a self-propelled condition without wheel slip, and with high drawbar pull (21.8 kN) and high wheel slip (27%), were compared in the clay loam agricultural field. The mechanical properties of the topsoil were determined in situ on the basis of vertical plate-penetration tests and horizontal plate-shear deformation tests with a tractor-mounted bevameter. Soil stress-strain conditions at contact with a traction tyre were reproduced in the laboratory by means of a direct simple shear box. A Geonor shear box was modified in order to carry out hydraulic conductivity measurements in saturated conditions while shearing the soil sample. Simulations with the soil-tractor interaction model matched measured traction performance with general good agreement (overall mean error of 12% and overall mean residual of 3.30 kN). As soon as the soil failure condition, as simulated by the model, was approached along the soil-tyre contact surface, longitudinal topsoil displacements measured in the silty loam agricultural field clearly increased. The slip values at which soil failure was reached were identified for three configurations of the 40 kN tractor. These slip values should be regarded as indicative limits not to be exceeded in tillage operations in order to avoid topsoil damage in the conditions under consideration. The stress state at the soil-tyre contact surface increased significantly, mostly in terms of shear stress, when the tractor moved with slip rather than without slip. As a consequence, the severity of tractor-traffic-induced soil degradation increased appreciably. The change in soil structure and hydraulic properties measured in the clay loam agricultural field was more pronounced in the first 0.15 m where the total porosity decreases by 11% without slip and 29% with slip, with a reduction in macropores of about 60% and 100%, respectively. The saturated hydraulic conductivity of the shallow topsoil (0 - 0.04 m) turned out to be reduced by about 66% without slip and about 98% with 27% slip. The results of the simple shear tests confirmed that shear deformations may contribute to damage topsoil structure functionalities, decreasing, in most cases, hydraulic conductivity. However, in the samples of clay, clay loam and silty loam, the major decrease in hydraulic conductivity was caused by the deformation during compression. Moreover, it emerged that the effects of shearing on the saturated hydraulic conductivity are mainly controlled by the volumetric strain coupled to the shear strain, and the variation in voids volume of the pore system affects the hydraulic conductivity more than a pure distortional deformation which may alter the water pathways in the sample. The validated approach for modelling tractor traction performance and predicting topsoil damage from the shearing effect due to tyre slip was used as a framework for developing a new Excel module for the third edition of the TASC V3.0.xlsm software: www.agrartechnik-agroscope.ch. This module also provides the power-wheel slip relationship. Four practical tests were set up for the user to enable a fast, simple and reliable mechanical characterisation of topsoil behaviour. Different tractor configurations, soil textures and conditions can be confronted. The limit beyond which topsoil damage is expected to occur is reported in terms of net traction and wheel slip. TASC V3.0 offers a valuable support tool for identifying tractor configurations and soil conditions which optimise traction, resulting in increased fuel saving, reduced tyre wear and limited topsoil damage.
Le lavorazioni dei terreni agricoli in molti casi richiedono elevate forze di trazione sviluppate dalle ruote dei trattori. Uno pneumatico da trazione interagisce con il terreno attraverso un sistema di tensioni lungo la superficie di contatto tra lo pneumatico e il terreno, tale interazione genera deformazioni sia nel terreno che nello pneumatico. Il terreno viene assoggettato a tensioni normali e tangenziali alla superficie di contatto con lo pneumatico. Le tensioni tangenziali aumentano repentinamente all’aumentare della forza di trazione e possono portare il terreno compresso tra le costolature del battistrada dello pneumatico in condizioni di rottura (effetto di taglio del terreno). Ciò determina la formazione di uno strato superficiale di terreno privo di resistenza meccanica e, quindi, fortemente esposto ai fenomeni erosivi, e uno strato sottostante in cui l’effetto delle deformazioni di taglio contribuisce ad alterare le funzionalità della struttura del terreno. Obiettivo di questo lavoro è l’indagine delle condizioni meccaniche all’interfaccia di contatto tra il terreno e lo pneumatico che generano suddetto danneggiamento del terreno. Tali condizioni meccaniche sono state analizzate e discusse sulla base di simulazioni con un modello di interazione terreno-pneumatico e secondo i risultati di specifiche prove sperimentali. Un modello semiempirico di interazione tra il terreno e una ruota pneumatica è stato adattato per simulare le prestazioni di trazione di trattori MFWD, considerando l’effetto di trasferimento del carico sulla ruota, l’effetto del passaggio multiplo sul terreno e il rapporto delle velocità teoriche tra gli assi anteriore e posteriore. Il modello è stato utilizzato per simulare (i) le prestazioni di trazione di trattori MFWD in termini di trazione netta, resistenza al movimento dovuta al compattamento del terreno, coefficiente di trazione ed efficienza di trazione, in funzione dello slittamento degli pneumatici, del carico sulla ruota e della pressione di gonfiaggio degli pneumatici; (ii) i percorsi di tensione del terreno lungo la superficie di contatto con lo pneumatico e (iii) il rischio di raggiungimento delle condizioni di rottura del terreno in corrispondenza di un definito slittamento. Numerose prove di trazione sono state eseguite su quattro terreni agricoli di differente tessitura (terreno argilloso, franco argilloso, franco limoso e sabbioso franco), utilizzando quattro trattori aventi potenza di 40.4 kW, 65 kW, 110 kW e 123 kW e peso di 25.3 kN, 40 kN, 66.7 kN e 68 kN. La configurazione dei trattori è stata variata modificando la pressione di gonfiaggio degli pneumatici, il peso del trattore e utilizzando doppi pneumatici. Lo slittamento è stato controllato in un intervallo di valori generalmente compresi tra 0% e 35%, in alcuni casi sono stati raggiunti valori più elevati fino a un massimo del 58%. L’effetto di taglio del terreno, dovuto allo slittamento degli pneumatici da trazione, è stato studiato sul terreno agricolo franco limoso attraverso la misura degli spostamenti longitudinali del terreno lungo i corridoi di esecuzione delle prove di trazione. Un sistema di strisce ortogonali al corridoio di avanzamento del trattore è stato tracciato con una vernice spray sulla superficie del suolo, al fine di visualizzare in modo semplice gli spostamenti del terreno. Le alterazioni delle proprietà idrauliche del terreno causate dalle deformazioni indotte dal passaggio del trattore di 40 kN sono state confrontate in un terreno franco argilloso in assenza di slittamento e con elevato slittamento (27%) e forza di trazione netta (21.8 kN). Le proprietà meccaniche del terreno sono state determinate in situ sulla base di prove di compressione verticale e prove di deformazione di taglio in direzione orizzontale eseguite con un bevameter installato su di un trattore. Le condizioni di tensione e deformazione del terreno al contatto con lo pneumatico sono state riprodotte in laboratorio per mezzo di una scatola di taglio semplice diretto della Geonor. Essa è stata modificata al fine di eseguire delle misure di conducibilità idraulica in condizioni di saturazione durante la fase di taglio del provino di terreno. Le simulazioni con il modello di interazione terreno-trattore hanno riprodotto le misure delle prestazioni di trazione con elevata fedeltà (errore medio del 12% e scarto medio di 3.3 kN). Quando la condizione di rottura del terreno (simulata dal modello) è stata raggiunta lungo la superficie di contatto terreno-pneumatico, gli spostamenti longitudinali misurati sulla superficie del terreno franco limoso sono aumentati in maniera evidente. I valori di slittamento corrispondenti al raggiungimento della condizione di rottura del terreno sono stati definiti per tre configurazioni del trattore di 40 kN. Tali valori, che possono essere considerati come limiti indicativi nelle condizioni analizzate, non dovrebbero essere superati nelle operazioni di lavorazione del terreno, al fine di evitarne il danneggiamento. Lo stato di stress al contatto terreno-pneumatico è aumentato significativamente in presenza di slittamento, principalmente in termini di tensioni di taglio, con un conseguente aumento apprezzabile del danneggiamento del terreno indotto dal traffico del trattore. Le alterazioni della struttura e delle proprietà idrauliche misurate nel terreno franco argilloso sono risultate più evidenti nei primi 0.15 m di profondità dove è stata misurata una riduzione di porosità totale dell’11% in assenza di slittamento e del 29% in presenza di slittamento, con una corrispondente diminuzione della macroporosità rispettivamente del 60% e del 100%. Le deformazioni indotte dalle ruote del trattore hanno ridotto la conducibilità idraulica in condizioni di saturazione dello strato più superficiale di terreno (0 - 0.04 m) di circa il 66% in assenza di slittamento e di circa il 98% in presenza di uno slittamento del 27%. I risultati delle prove eseguite con la scatola di taglio semplice hanno confermato che le deformazioni di taglio possono contribuire al danneggiamento delle funzionalità della struttura del terreno, riducendo, in molti casi, la conducibilità idraulica. Tuttavia, nei terreni argilloso, franco argilloso e franco limoso la riduzione complessiva di conducibilità idraulica è stata quasi esclusivamente causata dal processo di compressione. La variazione della conducibilità idraulica durante il processo di taglio è stata principalmente controllata dalle deformazioni volumetriche abbinate a quelle di taglio. La variazione di porosità ha influenzato la conducibilità idraulica più della deformazione distorsionale che può alterare i percorsi idraulici all’interno del provino. L’approccio proposto per la modellazione delle prestazioni di trazione e l’identificazione delle condizioni di danneggiamento del terreno dovute all’effetto di taglio causato dallo slittamento degli pneumatici da trazione è stato convalidato sperimentalmente e utilizzato per lo sviluppo di un nuovo modulo Excel per la terza edizione del software TASC V3.0.xlsm: www.agrartechnik-agroscope.ch. Questo modulo simula anche la relazione tra potenza erogata dal motore e slittamento delle ruote. Per permettere agli utilizzatori una semplice e affidabile caratterizzazione meccanica del terreno, sono state messe a punto quattro pratiche prove di campo. L’applicazione consente di confrontare numerose configurazioni del trattore, su vari terreni con differenti condizioni. Il limite oltre il quale è previsto un danneggiamento del terreno è riportato in termini di trazione netta e slittamento. Il TASC V3.0 rappresenta un valido supporto per identificare le configurazioni del trattore e le condizioni del terreno che ottimizzano le prestazioni di trazione, con conseguente riduzione dei consumi di carburante e limitazione dell’usura degli pneumatici e del danneggiamento del terreno.

Thesis (M.S.)--West Virginia University, 2007.
Title from document title page. Document formatted into pages; contains xii, 86 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 80-82).

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.

At the heart of long term sustainable soil management is chemical fertility through the retention of exchangeable cations. Many current concepts of cation exchange and its relationship with base cation availability remain unchanged over the past century. Despite considerable advancements in analytical techniques many methods used today would be familiar to our forefathers. Comparative studies were undertaken in this thesis to understand how techniques to measure exchangeable soil ions could be enhanced and matched to defined scenarios. The total amount of cations that can be retained electrostatically on soil surfaces is termed the cation exchange capacity (CEC). An ability to systematically and consistently measure CEC is an essential step in soil characterisation. Compulsive exchange methods (using either 1.0 M NH4OAc or 0.05 M BaCl2) at a fixed pH value for determining CEC were scrutinised but acknowledged to be prone to systematic artefacts. The relationship between soil pH, soil texture and CEC was soil specific. When the batch method was compared with the column leach method, the former was more consistent for all soils. For calcareous soils BaCl2 was more suitable but NH4OAc was more generally applicable. The CEC was consistently significantly greater by the compulsive technique when compared with the effective method. The NH4OAc extraction method was applied to soils contaminated with potentially toxic elements (PTEs). The exchangeable concentration of PTEs correlated with total PTE loading. However, the exchangeable Ca decreased with amendment rate confirming an exchange of sites by PTEs. The compulsive technique extracted PTEs that were significantly 2 negatively correlated with soil basal respiration, phosphatase activity, potential nitrification rate (PNR) and the soil microbial biomass carbon. This confirms that of this method is evaluating the bioavailable/bioreactive fraction. Soil cation exchange capacity and exchangeable base cations increased commensurate with the amendment loading of bentonite and charcoal. The exchange capacity was also soil specific. Following amendments, the exchange capacity was higher after six weeks than after thirty weeks. This means that the amendment performance became impaired with time perhaps as the fine soil particles coated the ameliorant causing a decline in CEC. The difference between the effective and compulsive CEC was described as the calculated CEC. This was very sensitive to soil pH and was confirmed in a detailed study at a site where pH plots were amended over a five decade period. As pH rose, so did the exchangeable fraction of Ca, Mg and K. As the pH declined, Al, Fe and Mn exchangeability increased. Extraction techniques must be sympathetic of the soil pH value. The quantification and characterisation of exchangeable cations remains as fundamental a component of soil science today as it was a century ago.

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.

ABSTRACT SOIL AND WATER ANALYSIS TECHNIQUES FOR AGRICULTURAL PRODUCTION Maral, Nuh M. Sc., Department of Chemistry Supervisor: Prof. Dr. G. inci Gö
kmen May 2010, 108 pages In Turkey, usage of increasing amounts of fertilizers and pesticides by some unconscious farmers cause soil pollution and soil infertility for the crop production. Usage of water in excessive amounts and/or in poor quality for irrigation creates problems during the plant production. So in this study, soil and water samples were analyzed by using simple and reliable techniques for the soil and water quality in laboratories of METU and Soil Fertilizer and Water Resources Central Research Institute Laboratory in Ankara. The soil and water samples were collected using the standard techniques from Ankara, Bolu, Ç
orum and Kirikkale. According to the soil test results, the textures of the soil samples are found as loam and clay loam. The total salt content of the soil samples are between 0.033 &ndash
0.063 % (w/w), meaning they are low salinity soils (total salt less than 0.15 % w/w). The pH of the soil samples are between 7.86&ndash
8.15, they are slightly alkaline. The phosphorus concentrations of soil samples are in a range 4.95 to 35.45 P2O5 kg/da. Some of the soil samples have too high phosphorus content (greater than 12 P2O5 kg/da). The potassium content of soil samples are found between 141&ndash
286 K2O kg/da, so the soil is efficient for crop production. Lime content of the soil samples is between 1.04&ndash
2.67 % (w/w) CaCO3. It means all of the soil samples are calcareous but it is not too high for the agricultural production. Organic matter content of soil samples are found between 0.83&ndash
2.04 % (w/w). This means the soils are limited in their organic matter content for the crop production. Analysis of 22 water samples yielded EC values between 0.384 &ndash
1.875 dS/m. Water samples have moderate to high-salinity (if EC values between 0.205 and 2.250 dS/m), yet these can be used for the irrigation of the crops. pH values of water samples are found between 7.18-8.10, meaning that they are slightly alkaline. Bicarbonate concentrations of 19 of the water samples are greater than 200 mg/L. These waters may not be suitable for irrigation of ornamental plants. All of the water samples, except water samples from Gö
lbaSi, have sodium absorption ratio (SAR) values between 1 and 9. Water samples with low SAR values, except water samples from Gö
lbaSi, can be used for irrigation of almost all soils with little danger of developing harmful levels of sodium. The Residual Sodium Carbonate (RSC) values of water samples Ankara Gö
lbaSi and Sincan-1 are greater than 2.50 meq/L and these water samples are not suitable for the irrigation. RSC values of Etimesgut, Sincan-2 and Kazan water samples are positive and lower than the value 2.00 meq /L. All the other water samples have negative RSC values so they are the safe to use for irrigation. It has been observed that development of practical field analysis techniques for all soil and water quality parameters may be possible with exception of micronutrient determination. For determining soil and water quality parameters in the rural areas there is a need to establish a small laboratory with necessary equipment and apparatus and training one or two farmers. With the experience gained in this study, some of these techniques may be adapted to the rural field applications, so soil and water may be tested by the farmers for better yields.

The purpose of this project was to develop a comprehensive analytical method for the characterization of soil by examining particle size, elemental composition, and percent organic matter in soil, and to determine its forensic applicability. In this study, five soils of varying geological locations were examined including two samples from Kentucky; two samples from Pennsylvania; and one from Washington D C A Gilson sonic sieve shaker was used to separate fractions of soil to determine particle size, and a JEOL scanning electron microscope with a Kevex EDS detector was used to determine elemental composition. These techniques coupled with percent total carbon analysis (determined with a LECO CHN-1000) provide a method that measures three forensic properties instead of one for the forensic comparison of soil.

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

ELETROBRAS TERMONUCLEAR S.A - ELETRONUCLEAR
Neste trabalho o método dos elementos finitos é empregado para analisar a estabilidade de taludes em solo solapados por voçorocas. Muitos dos deslizamentos de solo que ocorrem em taludes e encostas têm sido causados pelo fenômeno de voçorocas, o resultado de um processo de erosão de solos muito complexo. Uma breve revisão sobre a formação e o crescimento de voçorocas, bem como sobre os seus efeitos na estabilidade de taludes em solo, é feita neste trabalho. Exemplos ilustrativos da aplicação desta técnica para alguns casos de taludes e encostas erodidos por voçorocas são apresentados, incluindo-se duas análises numéricas da estabilidade de encostas situadas na cidade de Goiânia - GO. Dificuldades numéricas devido à baixa taxa de convergência da solução nas proximidades do colapso do talude são também discutidas.
In this work the finite element method is employed to analyze the stability of soil slopes undermined by voçorocas (gulling). Many of the shear slides occurred in both natural slopes and embankments have been caused by the phenomenon of voçorocas, the outcome of a very complex soil erosion mechanism. A brief review about the formation and growing of voçorocas, as well as an overview of their effects on soil slope stability, are made in this work. In the numerical simulation by the finite element method, the potential slip surface is identified through the progressive formation of a region of yielded soil as the erosion process advances. A simple model, consisting of incremental excavations of soil near the foot of the slope, is used in this work to represent the undermining mechanism. Illustrative examples of this technique are presented for some cases of natural soil slopes eroded by voçorocas in the city of Goiania - GO. Numerical difficulties due to the poor convergence of the solution near the soil collapse are also discussed.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Comumente as análises de estabilidade de taludes são realizadas mediante métodos determinísticos, os quais visam o cálculo de um fator de segurança único assumindo os valores dos parâmetros de resistência como representativos e fixos. Estes métodos não conseguem avaliar as incertezas existentes nas propriedades do solo e tampouco indicam a proporção de influência que tem cada parâmetro de resistência no valor do fator de segurança. Os métodos probabilísticos, com base nas teorias de probabilidade, confiabilidade e estatística, permitem estimar a influência dessas incertezas nos cálculos determinísticos, com a possibilidade de prever mais amplamente o risco de insucesso associado a um projeto geotécnico de estabilidade de taludes. O presente trabalho estuda a aplicação de três métodos probabilísticos (Monte Carlo, Hipercubo Latino e Estimativas Pontuais Alternativas) na avaliação de estabilidade de taludes, com auxílio de métodos de equilíbrio limite no cálculo do fator de segurança. Com objetivo de inferir o impacto das variáveis aleatórias nas estimativas de probabilidade e confiabilidade, bem como da importância de uma quantificação adequada dos valores de desvio padrão, são realizadas comparações dos resultados obtidos com métodos probabilísticos e determinísticos (método das fatias, método dos elementos finitos) discutindo as principais vantagens, dificuldades e limitações nas aplicações dos mesmos em problemas de estabilidade de taludes de solo.
Slope stability analyses are usually carried out using deterministic methods, which aim the calculation of a single safety factor assuming the values of the shear strength parameters as representative and fixed. These methods fail to assess the uncertainties in soil properties and do not indicate the proportion of influence that each resistance parameter has on the final value of the safety factor. The probabilistic methods, based on probability, reliability and statistical theories, allow the estimation of the influence of these uncertainties on the deterministic calculations, with the possibility to broadly predict the risk of failure associated with a geotechnical slope stability project. This dissertation studies the application of three probabilistic methods (Monte Carlo, Latin Hypercube, and Alternative Point Estimates) in the evaluation of slope stability, with aid of limit equilibrium methods for the calculation of safety factors. In order to infer the impact of random variables on the estimates of probability and reliability, as well as the importance of an adequate quantification of the standard deviation values, comparisons are made among the results obtained with probabilistic and deterministic methods (limit equilibrium method, finite element method), discussing the main advantages, difficulties and limitations in their application to soil slope stability problems.