[pt] Esta dissertação tem como objetivo principal estudar um caso real do comportamento de taludes de grande altura em um projeto de mineração situado no Peru, em termos de deslocamentos e fatores de segurança, considerando uma escavação com uma profundidade que se aproxima de 900 m. As análises tensão x deformação foram executadas pelo método dos elementos finitos, em modelos bi e tridimensionais, considerando o modelo constitutivo de Mohr-Coulomb para os seis diferentes tipos de rocha encontrados na área do projeto. Também foram investigados os efeitos da geometria 3D em análises pseudo-estáticas, tendo em vista a mineração estar situada em região de atividade sísmica, bem como a distância da pilha de material estéril em relação à borda da escavação. De modo geral observou-se que os deslocamentos horizontais e o fator de segurança estático são maiores em analises 3D, enquanto que os deslocamentos verticais resultaram superiores nas análises 2D. Os efeitos da pilha de estéril nos valores do fator de segurança foram pouco significativos, mas a configuração da superfície potencial de ruptura varia de acordo com a distância da pilha à escavação. O fator de segurança pseudo-estático em análises 3D depende da orientação considerada para a força pseudo-estática horizontal. / [en] The main objective of this thesis is to investigate the mechanical behavior of rock slopes of great height in a mining project located in Peru, in terms of displacements and safety factors, considering that the excavation has almost reached the depth of 900m. The stress – strain analyses were carried out by the finite element method considering bi and three-dimensional models and the Mohr-Coulomb constitutive model for the six different types of rock found in the area of the project. The 3D geometrical effects on pseudo-static analyzes were also investigated, since the mine is situated in a region of seismic activity, as well as the influence of the distance of the waste material from the edge of the excavation. In general, it was observed that the horizontal displacements and the static safety factor are larger in 3D analysis while the vertical displacements were superior in 2D models. The effects of the waste dump on the values of the safety factor were insignificant, but the configuration of the potential failure surface varied according to its distance from the excavation. The pseudo-static safety factor in 3D analysis depends on the orientation considered for the horizontal pseudo-static force.

Apresenta-se um estudo paramétrico acerca da infiltração de água e sua repercussão no Fator de Segurança de talude em solos não saturados. Na análise adota-se um talude de referência com geometria fixada conforme a inclinação típica para taludes em areia argilo siltosa, característica do Centro-Oeste do estado de São Paulo. A análise paramétrica foi desenvolvida a partir de uma simulação de fluxo em regime transiente utilizando o programa SEEP/W, que utiliza o método de elementos finitos, e posteriormente uma análise de estabilidade do talude de referência utilizando o método de Bishop simplificado conforme apresentado no programa SLOPE/W. Foram analisados taludes homogêneos compostos por três diferentes tipos de solo, uma areia, um silte argiloso e uma areia argilo siltosa. Os parâmetros analisados compreendem a curva de retenção de água, a função condutividade hidráulica do solo e a intensidade de precipitação. Verificou-se que a função condutividade hidráulica e a pressão de entrada de ar são os principais determinantes do comportamento da infiltração e conseqüentemente da estabilidade do talude. As simulações de fluxo evidenciaram que os taludes em solos mais arenosos apresentam taxas de infiltração maiores que as apresentadas pelos taludes compostos por solos siltosos. Consequentemente, os escorregamentos ocasionados pela perda da contribuição da sucção para a resistência ao cisalhamento ocorrem primeiramente nos taludes compostos por solos arenosos e posteriormente naqueles compostos por solos siltosos, fato este que pôde ser confirmado pelas análises de estabilidade do talude de referência. / A parametric study is presented about water infiltration and its repercussion in the safety factor of unsaturated soil slopes. In the analysis it is adopted a reference slope with determined geometry according to the typical inclination for slopes in silty clayey sand, characteristic of the mid-western region of São Paulo State, in Brazil. The parametric analysis was developed from a flux simulation in transient regime using the SEEP/W software, which uses the finite elements method, and thereafter, a stability analysis of the reference slope using simplified Bishop method, as presented in the SLOPE/W software. Homogeneous slopes composed by three different types of soil (sand, clayey silt and silty clayey sand) were considered. The analyzed parameters include the water retention curve, the hydraulic conductivity function and the precipitation intensity. It was verified that the hydraulic conductivity function and the air entry value are the main determinants of the infiltration behavior and, subsequently, of the slope stability. The flux simulations have evidenced that coarser soils slopes show higher infiltration rates than the ones presented in finer soil slopes. Consequently, the slides caused by the loss of the suction\'s contribution to shear strength occur primarily in coarser soil slopes than in fine soil slopes, what could be verified in the stability analysis of the reference slope.

Apresenta-se neste trabalho uma análise de ruptura de um talude em solo não saturado. O talude, com cerca de 15 m de altura, é composto de areia fina a média argilosa, com grau de saturação da ordem de 55% e SPT variando entre 4 golpes no topo a 13 golpes na base. Determinaram-se as seguintes propriedades do solo: resistência, condutividade hidráulica saturada e não saturada e curva de retenção, além de medir-se a sucção matricial em campo ao longo do ano. Efetuaram-se análises paramétricas para avaliar o efeito da precipitação na mudança do perfil de sucção matricial do terreno e suas implicações na resistência e, por extensão, na estabilidade do talude. Construíram-se, também, ábacos que incluem o efeito da variação da sucção matricial, utilizáveis para taludes com características semelhantes ao talude estudado. Verificou-se que para as condições do talude natural, no auge da estação seca, as sucções matriciais são de tal magnitude que fornecem estabilidade ao talude. À medida que ocorrem precipitações, as sucções matriciais reduzem-se e o fator de segurança do talude diminui, o que justifica a ruptura ocorrida. / In this article is showing an slope back analysis in unsaturated soil. The slope, with about 15 m of height, it is composed of a fine to medium clayey sand, with degree of saturation of the order of 55% and SPT varying among 4 blows in the top to 13 blows in the base. The following properties of the soil were determined: resistance, saturated and unsaturated conductivity and it curves of retention, besides measuring the suction along the year. Parametric analyses were made to evaluate the effect of the precipitation in the changes of the ground matricial suction profile and its implications in the resistance and, by extension, in the slope stability. They were also made, some abaci that include the effect of the matricial suction variation, usable for slopes with similar characteristics to the studied slope. It was verified that for the conditions of the natural slope, next to the peak of the dry station, the matricial suction is of such magnitude that it supply stability to the slope. In the successive events of precipitations the matricials suctions is reduced and the slope security factor decreases, that justifies the happened rupture.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-26T09:23:06Z No. of bitstreams: 2 Dissertação - Emilly Dias da Silva - 2016.pdf: 6131512 bytes, checksum: 2ebac9ad8e2116f4ee2c3159379816ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-26T09:23:41Z (GMT) No. of bitstreams: 2 Dissertação - Emilly Dias da Silva - 2016.pdf: 6131512 bytes, checksum: 2ebac9ad8e2116f4ee2c3159379816ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-26T09:23:41Z (GMT). No. of bitstreams: 2 Dissertação - Emilly Dias da Silva - 2016.pdf: 6131512 bytes, checksum: 2ebac9ad8e2116f4ee2c3159379816ca (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-01-29 / The use of soil nailing technique can be an important alternative for the stabilization of a slope or an excavation. Nails are retaining elements that reinforce soil masses acting passively, requiring strains to mobilize their resistance. The mechanical behavior analysis of a structure with soil nailing technique can be made using limit equilibrium methods, being represented by loads applied to reinforcing layers or sub-horizontal slices of a slope. The slice has its base crossed by a reinforcing action line and the reinforcing nail is treated as a concentrated point load acting on the base point of intersection of a slice with the line of action. Thus, through analytical and numerical calculations, this dissertation studied the design of soil nailing structure considering variations of suction, which influences the soil resistance, simulating suction profiles of a typical soil of the Brazilian Midwest region. This study was conducted determining strength parameters on nail-soil interface by tests in the field, i.e. nail pullout tests, and soil strength and hydromechanical parameters determined in the laboratory. For this, two separate suction sections were studied, and in each case, numerically analyzed in soil nailing structures, obtaining the dimensions of the structure through a pre-sizing phase, and then analyzing the factor of safety of the structure using computer programming considering the Bishop method. In the first case, the distribution of suction was numerically simulated for the soil profile studied in a critical condition of rainfall in Goiania region. Then, the suction field profile was obtained for comparison with the first case. With the results of this research, it was possible to understand the increasement of resistance and safety fator of the structure when considering the suction effects at the design of soil nailed structures in a typical soil of Goiânia region. / A utilização de contenções em solo grampeado pode ser uma importante alternativa para a estabilização de um talude ou de uma escavação. Os grampos ou tirantes passivos são elementos de contenção ou de reforço de massas de solo que agem passivamente, requerendo deformações para mobilizar sua resistência. A análise do comportamento mecânico de uma estrutura onde existe solo grampeado pode ser feita através de métodos de equilíbrio limite, sendo representada por cargas de reforço aplicadas a camadas ou fatias sub-horizontais de um talude. A fatia tem a sua base atravessada por uma linha de ação de reforço e a carga de reforço é tratada como uma carga pontual concentrada agindo no ponto de intersecção da base de uma fatia com a linha de ação. Assim, através de cálculos por ferramentas analíticas e numéricas, o presente trabalho estudou o dimensionamento da estrutura de solo grampeado considerando a variação de sucção, que influencia a resistência do solo, simulando perfis de sucção de um solo típico da região do centro oeste brasileiro. Esse estudo foi realizado determinando parâmetros de resistência na interface grampo-solo por ensaios realizados em campo, como ensaios de arrancamento de grampo, e parâmetros de resistência e hidromecânicos do solo não saturado determinados em laboratório. Para isso, foram estudados dois perfis de sucção distintos e, para cada caso, analisou-se numericamente a estrutura de contenção em solo grampeado, obtendo-se as dimensões da estrutura através de um pré-dimensionamento, e, a seguir, analisando o fator de segurança da contenção utilizando programação computacional considerando o método de Bishop. No primeiro caso foi simulada numericamente a distribuição do perfil de sucção do solo estudado para uma condição de precipitação crítica na região de Goiânia. No segundo, foi obtido o perfil de sucção de campo para comparação com o primeiro caso. Com os resultados desta pesquisa, foi possível compreender o aumento da resistência e do fator de segurança da contenção ao considerar os efeitos de sucção no dimensionamento de uma estrutura de contenção em solo grampeado típico da região de Goiânia.

Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-01-30T10:00:16Z No. of bitstreams: 2 Dissertação - Victor Scartezini Terra - 2016.pdf: 3940729 bytes, checksum: 27241c105d696ce18e125b5eb6c44691 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-30T10:04:56Z (GMT) No. of bitstreams: 2 Dissertação - Victor Scartezini Terra - 2016.pdf: 3940729 bytes, checksum: 27241c105d696ce18e125b5eb6c44691 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-30T10:04:56Z (GMT). No. of bitstreams: 2 Dissertação - Victor Scartezini Terra - 2016.pdf: 3940729 bytes, checksum: 27241c105d696ce18e125b5eb6c44691 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-08-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Natural disasters related to landslides have caused thousands of deaths and left tens of thousands homeless people around the world. Landslides can occur in most cases due to factors related to water infiltration on soil, causing a raise in the positive pore-water pressure. But what is often observed is that both water infiltration and the reduction of negative pore-water pressure due to water infiltration are not, in practice, enough to justify some of the observed landslides. Some less conventionals mechanisms, such as lightning, are not, usually, taken in consideration in a failure analysis, but can contribute to the factor of safety reduction. This paper aims to study the effects of atmospheric discharges in the stability of natural slopes of residual soils. Partial differential equations governing the coupled flow of pore-water and pore-air are developped. The numerical modeling is made with the FlexPDE software, version 6. The results show that there is a raise on pore-air pressure inside the soil due to atmospheric discharge. However, the raise of pore-air pressure works both in the raise of the apparent cohesion and the reduction on net pressure. It is concluded that any failure due to atmospheric discharge will present a shallow slip surface. / Desastres naturais relacionados a deslizamentos de massas de terra já causaram milhares de mortes e dezenas de milhares de desabrigados no mundo inteiro. Os deslizamentos podem ocorrer em sua maioria devido aos fatores provenientes da infiltração de água no solo, gerando aumento das poropressões positivas de água. Mas o que se observa frequentemente, é que a infiltração e a redução das poropressões negativas muitas vezes não são, na prática, o suficiente para justificar todos os escorregamentos observados. Mecanismos menos convencionais como descargas atmosféricas e o aumento das poropressões de ar consequentes do efeito Lisse normalmente não são levados em consideração em análises de ruptura, mas podem contribuir para a diminuição do fator de segurança de taludes. Esta pesquisa tem como objetivos, portanto, estudar como os efeitos do avanço da frente de infiltração e das descargas atmosféricas irão afetar a estabilidade de taludes em encostas naturais de solos residuais. Além disso, cita-se como objetivos secundários o desenvolvimento de modelos numéricos para análises acopladas de fluxo de água e ar, e a verificação desses modelos por meio de análises de validação. Um estudo detalhado de como a onda de choque e os gradientes de temperatura de descargas atmosféricas se comportam ao atingir a superfície terrestre é desenvolvido para que se possam definir as condições de fronteira do problema. Equações diferenciais parciais acopladas para fluxo de água e ar são desenvolvidas. As análises são feitas com o auxílio do programa FlexPDE, versão 6. Os resultados mostraram que há um aumento das poropressões de ar na massa de solo provenientes de descargas atmosféricas ou do efeito Lisse. No entanto, tais acréscimos de poropressão de ar trabalham tanto a favor do ganho de coesão aparente como como na diminuição das tensões líquidas. No estudo da influência do aumento das poropressões de ar como consequência de descargas atmosféricas conclui-se que eventuais rupturas de taludes causadas por isso serão rasas. Com relação ao estudo do aumento de poropressão de ar em taludes como consequência do efeito Lisse, conclui-se que os acréscimos de poropressão de ar serão maiores na massa de solo quando mais próximo da saturação estiver o solo.

Vegetation can increase the resistance of slopes against landsliding. The mechanical contribution of roots to the shear strength of the soil is however difficult to measure in situ. Existing methodologies are time-consuming and therefore not suitable to quantify spatial variability on the slope. Furthermore, some existing methods, for example large in situ shear box testing, can be difficult to apply on remote sites with difficult access, e.g. steep slopes. Therefore in this thesis novel, simple and portable methods to quantify mechanical root-reinforcement in the field were developed. The ‘blade penetrometer method’, one of these new methods, was based on standard penetrometer testing but used an adapted tip shape to increase sensitivity to roots. Root depths and diameters could be quantified based on characteristics of the depth–resistance trace, both in the laboratory and in the field. Several new analytical interpretive models were developed to predict the force–displacement behaviour of roots loaded under various conditions: one assuming roots broke in tension and another assuming roots broke in pure bending. Both methods did take root–soil interaction into account. Based on these models, some roots were shown to have broken in bending and others in tension, depending on plant species and root diameter. Two new methods were developed to measure the root-reinforced soil strength directly. The ‘pin vane’ was an adaptation of a standard field shear vane, replacing the cruciform blades of the latter by prongs to minimise the effects of soil disturbance and root breakage during installation. This was one of the main problems encountered when using standard vanes in rooted soil. This ‘pin vane’ method was qualitatively shown to be able to measure the reinforcing effects of both fine and thick roots (or root analogues), both in the laboratory and the field. This method will be most useful when the strength of densely rooted surface layers is to be analysed, e.g. for erosion resistance purposes. Another newly developed shear device was the ‘corkscrew’. Rotational installation of the screw ensured minimal soil and root disturbance. During vertical extraction the root-reinforced shear strength was mobilised along the interface of the soil plug caught within the screw. The measured extraction force could be related to the reinforced soil strength. This method underestimated the strength in surface layers (especially at 0–125 mm and less so at 125–250 mm depth) but functioned well in deeper soil layers important for landsliding. Although laboratory results were promising, during in situ testing in deeper layers ( > 125 mm) local variation in soil stress, gravel content and water content, combined with low root volumes, made it difficult to accurately quantify the effect of the roots. Where the effect of roots was pronounced, e.g. in more heavily rooted surface layers (0–125 mm), significant positive trends between the measured soil strength and root strength and quantity were found. Measured reinforcements were small compared with various root-reinforcement model predictions but comparable to direct shear tests on rooted soil reported by others. These new methods, although still in the early stages of development, showed promising results for practical use in field conditions. The equipment was simple to use and portable, enabling measurements on sites with difficult accessibility. However, more work is required to validate the interpretive models developed and to calibrate these methods for a wider range of soil and root conditions.

Placing a geomembrane liner in the core of a dam is an alternative construction technique to traditional clay core types. This study aims to assess the performance of such internal geomembrane sealing systems in an earthen dam. Two-dimensional (2D) numerical analysis was performed to evaluate leakage through defective seams within an earthen dam. Five possible applications of internal geomembrane systems were initially modeled to locate the zero-pressure lines in an earthen dam. Then, another application where the geomembrane is placed on the upstream face was modeled to compare the upstream and internal geomembrane systems. The results of this study show that use of a geomembrane system, either upstream or internal, significantly decreases the pore pressure at the downstream face of the earthen dam. In addition, limit equilibrium analysis was performed to evaluate the effects of leakage through defects in geomembranes on the dam stability. The stability analyses for the upstream and downstream slopes were performed for three loading conditions: (1) end of construction, (2) long-term, and (3) rapid drawdown. The frequencies and locations of defective seams had a significant impact on the factors of safety of the downstream slope. It is shown that, in the case of upstream geomembrane systems, the factor of safety for the downstream slope has the highest value when the geomembrane hole occurs at a relatively lower location. On the other hand, in the case of internal geomembrane systems, the highest factor of safety occurs when the geomembrane hole is at a higher location. Additionally, rapid drawdown simulations show that the upstream slope of an embankment dam must be flat enough to overcome the upstream stability issues when geomembranes are placed within embankment dams. This study not only showed the advantages of using a geomembrane in the core of a dam as an impervious lining system but also provided comparative information on the performance of internal and upstream geomembrane systems with respect to the stability in earthen dams.

Slope stability is an important aspect of geotechnical engineering. Input parameters for the analysis are the governing factors and they must be determined accurately and precisely. Field investigations, laboratory testing and back analyses are vital instruments for the input parameters. This study presents the results of slope stability analysis for the soil slopes at Elbistan-&Ccedil / &ouml / llolar lignite mine. After executing the drilling programme, samples taken from the drilling work, delivered to soil mechanics laboratory for testing. The basic input parameters, namely cohesion and friction angle determined at soil mechanics laboratory were compared to the parameters obtained from back analysis of a large scale slope failure. Input parameters for the analysis are determined by this way. After determining the input parameters, slope stability analyses were carried out both for the permanent and temporary slopes in AfSin-Elbistan lignite basin, &Ccedil / &ouml / llolar sector. The effect of ground water on the stability of slopes was investigated in detail and maximum safe slope angles were determined for different water levels. For limit equilibrium analysis, Rocscience SLIDE software, for finite difference analysis in 3-D, Itasca FLAC3D was used. In the limit equilibrium analyses both circular and composite failures were considered. Shear strength reduction method is used for the finite difference method. The results between limit equilibrium and 3-D finite difference methods were compared. When the failure surfaces obtained from the finite difference analyses were imposed to limit equilibrium analysis, computations are resulted in lower factor of safety values for limit equilibrium analysis.

Shear strength characterization of discontinuities is an important concept for slope design in discontinuous rocks. This study presents the development of a methodology for implementing Barton-Bandis empirical shear strength failure criterion in three dimensional distinct element code, 3DEC, and verification of this methodology. Normal and shear deformation characteristics of discontinuities and their relations to the discontinuity surface characteristics have been reviewed in detail. First, a C++ dynamic link library (DLL) file was coded and embedded into 3DEC for modelling the Barton-Bandis shear strength criterion. Then, a numerically developed direct shear test model was used to verify the normal and shear deformation behaviour with respect to empirical results of the Barton-Bandis shear strength criterion. A three dimensional simple discontinuous rock slope was modelled in 3DEC based on Barton-Bandis shear strength criterion. The slope model was first utilized by Mohr-Coulomb failure criterion. Then, with the use of the new model developed here, the effects of the discontinuity surface properties on shear strength were introduced to the slope problem. Applicability of the developed model was verified by three large scale real case studies from different open pit lignite mines of Turkish Coal Enterprises (TKi), namely Bursa Lignites Establishment (BLi) &ndash / 2 cases and &Ccedil / an Lignite Establishment (&Ccedil / Li). The results with the new model option, which allows users to use important discontinuity surface properties like joint roughness coefficient and joint wall compressive strength, compared well with results of previous studies using Mohr-Coulomb failure criterion.

Groundwater can be a critical issue to be considered in civil engineering, mining engineering and interdisciplinary fields. Karstic structures and aquifers enclosing groundwater are potential risks in case they are not studied in detail. Enclosed groundwater can result in floods at pit bottom or can cause instabilities of permanent pit slopes. This study is about analyses of flooding possibility at the pit bottom and possible instabilities of pit slopes in the Elbistan-&Ccedil / &ouml / llolar open cast coal mine due to the presence of a karstic aquifer under the lignite formation. Thickness and permeability of the bottom clay formation under the lignite bed are necessary critical parameters for investigating a possible water rush from a confined aquifer in limestone formation underneath the bottom clay. These parameters were changed, and water flow quantities towards the pit bottom were determined by finite element models. Critical values of these parameters were investigated considering the lack of accurate site investigation information regarding the thickness and permeability of bottom clay. Possible strength loss, fracturing, and thus permeability increase in bottom clay due to a confined aquifer were studied. In flooding and slope stability analyses Phase2 software based on finite element method is used. Results of analyses showed that as reported thickness of bottom clay is around 120 m at the pit bottom and permeability values are in orders of magnitudes of 10-8 m/s, no serious flooding problems are expected to occur unless the thickness of bottom clay layer drops down to around 20 m, and the permeability of this layer reaches an order of magnitude of 10-5 m/s. Mechanical effects of confined aquifer on slopes and bottom clay displacements were investigated, and thus fracturing and failure possibilities of bottom clay and permanent slope were assessed. Slope and pit bottom displacements increased to meter levels for less than 60 m bottom clay thicknesses. Whereas 50-60 m bottom clay thickness can be critical for cracking, 20 m bottom clay thickness was found to be critical for water rush to the pit bottom. With reported bottom clay thickness of 120 m and with 25o slope angle permanent slope factor of safety was found to be 1.2, and this value was not effected unless clay layer thickness drops below 70 m levels. Higher than 32o overall slope angle there will be a risk of slope failure for permanent and production slopes, reflected by safety factors less than one, in the stability analyses.