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Yes / The instability of soil slopes is directly related to both the shear parameters of the soil material and the groundwater, which usually causes some uncertainty. In this study, a novel method, the element failure probability method (EFP), is proposed to analyse the failure of soil slopes. Based on the upper bound theory, finite element discretization, and the stochastic programming theory, an upper bound stochastic programming model is established by simultaneously considering the randomness of shear parameters and groundwater level to analyse the reliability of slopes. The model is then solved by using the Monte-Carlo method based on the random shear parameters and groundwater levels. Finally, a formula is derived for the element failure probability (EFP) based on the safety factors and velocity fields of the upper bound method. The probability of a slope failure can be calculated by using the safety factor, and the distribution of failure regions in space can be determined by using the location information of the element. The proposed method is validated by using a classic example. This study has theoretical value for further research attempting to advance the application of plastic limit analysis to analyse slope reliability. / National Natural Science Foundation of China (grant no. 51564026), the Research Foundation of Kunming University of Science and Technology (grant no. KKSY201904006) and the Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province (grant no. ZJRM-2018-Z-02).

Based upon the upper bound limit analysis, the stability numbers have been developed for a two-layered soil slope both for an associated flow rule material and for a homogeneous slope with non-associated flow rule material. The failure surface was assumed to be an arc of logarithmic spiral and it automatically ensures the kinematics admissibility of the failure mechanism with respect to the rigid rotation of the soil mass about the focus of the logarithmic spiral. The effect of the pore water pressure and horizontal earthquake body forces was also included m the analysis. For a non-associated flow rule material, the stress distribution along the failure surface was developed with the assumption of interslice forces given by Fellenius and Bishop. The stability numbers have been found to reduce appreciably with increases m the (i) horizontal inclination (β) of slope, (ii) pore water pressure coefficient, ru and (iii) horizontal earthquake acceleration coefficient (kh). The values of the stability numbers for a non-associated co-axial flow rule, with dilatancy angle ψ =0, have been found to be considerably lower as compared to the associated flow rule material. For a given height of the slope, with associated flow rule, the values of the stability numbers have been found to increase with increase in the thickness of a layer with greater value of the friction angle Φ. The results have been given in the form of non-dimensional stability charts, which can be used for readily obtaining either the value of the critical height or the factor of safety The methodology can be easily extended even for multi-layered soil slopes with different values of cohesion (c), bulk unit weight (γ) and friction angle (Φ). An attempt has also been made in this thesis to study experimentally the effect of the frequency of the excitation and the addition of non-plastic fines on the liquefaction resistance of the material Shake table studies, generating uni-axial sinusoidal horizontal vibrations, were earned out for this purpose. During the period of excitation of the material, the settlement at the surface of the sample increases continuously with time up to a certain peak value and thereafter, it becomes almost constant. For the excitation of the material with higher frequency, more number of cycles was seen to reach the final settlement. With the continuous excitation of the material, the magnitude of the pore water pressures increases up to a certain peak value and there after, its magnitude decreases till it again becomes the hydrostatic pressure as it was before the excitation of the material. The peak magnitude of the pore water pressure tends to be higher for the excitation with smaller frequency especially at greater depths from the ground surface. The addition of non-plastic fines tends to increase the magnitude of the settlement as well as the increase in the pore water pressure.

Esta pesquisa investigou os processos de gênese dos NITOSSOLOS VERMELHOS Férricos, buscando compreender quais os fatores que levam a diferenciação entre Nitossolos típicos, nos quais encontramos a sequência de horizontes A-Bni-C e Nitossolos latossólicos, mais comuns, de sequência A-Bni-Bw-C. A área de estudos é a bacia do córrego Miringuava, situada no município de Maringá-PR. Esta pequena bacia se insere em um setor da bacia do ribeirão Pinguim no qual ocorre uma transição, entre duas áreas de domínio latossólico, uma no alto curso do Pinguim, outra no baixo curso. A área apresenta-se dominada por Nitossolos e por associações entre Cambissolos e Neossolos Litólicos, que ocorrem devido à presença de diques de diabásio relacionados aos derrames basálticos da Formação Serra Geral. Para atingir este objetivo, investigamos a relação entre a declividade e a posição destes solos nas vertentes, a ocorrência de transporte de argila no interior destes perfis e sua eventual relação com a formação dos horizontes B níticos (Bni) e por fim, a relação da evolução destes sistemas pedológicos com a evolução do relevo regional. Os procedimentos adotados no estudo seguem a abordagem da Análise Estrutural da Cobertura Pedológica, proposta por Boulet (1982 a, b, c). Os resultados mostram que há uma relação entre declividade e a posição destes solos na vertente, embora não seja possível estabelecer um limite que possa ser extrapolado para toda a bacia do Pinguim. Revelam ainda indícios que apontam para processos de eluviação/iluviação nos perfis estudados e, por fim, que provavelmente os horizontes Bni se formaram a partir de antigos horizontes B latossólicos (Bw), como os encontrados no alto curso do ribeirão pinguim, e que há um processo atual de degradação dos horizontes Bni, que ocorre através da fragmentação de sua estrutura poliédrica em uma estrutura microagregada, sugerindo que há um processo de latossolização destes sistemas, que provavelmente evoluirão para uma cobertura pedológica semelhante à encontrada no setor do baixo curso do ribeirão Pinguim, dominado por Latossolos eutróficos. / This research investigated the genetic processes which give origin to the Red ferric Nitisols, trying to understand which factors lead to the differentiation between the typical Nitisols, with a horizon sequence A-Bni-C and the latosolic Nitisols, the most common type, with an A-Bni-Bw-C horizon sequence. The study area is the Miringuava Creek basin, located in the municipality of Maringá-PR, Brazil. This small hydrographic basin is placed in a sector of the Pinguim Creek basin, in which occurs a transition between two sectors dominated by Latosols, one in the high course of the Pinguim Creek and the other in the low course. The area is dominated by Nitisols and associations of shallow, poorly developed soils, which occur due to the presence of diabase dikes related to the basalts of the Serra Geral Formation. In order to accomplish the goal of this work, we investigated the relationship between slope and the positions of the soils in the hillslopes, clay transportation within the soil systems and finally, the relation between soil coverage and regional landform evolution. The procedures adopted for this research are based on the Structural Analisys of the Pedologic Coverage, proposed by Boulet (1982, a, b, c). The results show a relationship between slope and soil position, although it wasn´t possible to establish a limit which could be extrapolated for the entire area of the Pinguim Creek basin. The results also reveal evidence which point towards clay migration within the soil profiles studied in this work and finally, point to an evolution process in which the nitic horizons are formed from older latosolic horizons, such as the ones found in highest sectors of the Pinguim Creek basin, and that there is a present process of degradation of the nitic horizons, which through the fragmentation of the blocky structures into microgranular ones, suggesting that the Nitisols are evolving into younger eutrofic Latosols, similar to the ones found in the sectors of the low course of the Pinguim Creek.

The performance and safety assessment of geo-structures is strongly affected by uncertainty; that is, both due a subjective lack of knowledge as well as objectively present and irreducible unknowns. Due to uncertainty in the non-linear variation of the matric suction induced effective stress as a function of the transient soil-atmosphere boundary conditions, the unsaturated state of the subsoil is generally not accounted for in a deterministic slope stability assessment. Probability theory, accounting for uncertainties quantitatively rather than using "cautious estimates" on loads and resistances, may aid to partly bridge the gap between unsaturated soil mechanics and engineering practice. This research investigates the effect of uncertainty in soil property values on the stability of unsaturated soil slopes. Two 2D Finite Element (FE) programs have been developed and implemented into a parallelised Reliability-Based Design (RBD) framework, which allows for the assessment of the failure probability, failure consequence and parameter sensitivity, rather than a deterministic factor of safety. Utilising the Random Finite Element Method (RFEM), within a Monte Carlo framework, multivariate cross-correlated random property fields have been mapped onto the FE mesh to assess the effect of isotropic and anisotropic moderate heterogeneity on the transient slope response, and thus performance. The framework has been applied to a generic slope subjected to different rainfall scenarios. The performance was found to be sensitive to the uncertainty in the effective shear strength parameters, as well as the parameters governing the unsaturated soil behaviour. The failure probability was found to increase most during prolonged rainfall events with a low precipitation rate. Nevertheless, accounting for the unsaturated state resulted in a higher slope reliability than when not considering suction effects. In a heterogeneous deposit failure is attracted to local zones of low shear strength, which, for an unsaturated soil, are a function of both the spatial variability of soil property values, as well as of the soil-water dynamics, leading to a significant increase in the failure probability near the end of the main rainfall event.

Esta pesquisa investigou os processos de gênese dos NITOSSOLOS VERMELHOS Férricos, buscando compreender quais os fatores que levam a diferenciação entre Nitossolos típicos, nos quais encontramos a sequência de horizontes A-Bni-C e Nitossolos latossólicos, mais comuns, de sequência A-Bni-Bw-C. A área de estudos é a bacia do córrego Miringuava, situada no município de Maringá-PR. Esta pequena bacia se insere em um setor da bacia do ribeirão Pinguim no qual ocorre uma transição, entre duas áreas de domínio latossólico, uma no alto curso do Pinguim, outra no baixo curso. A área apresenta-se dominada por Nitossolos e por associações entre Cambissolos e Neossolos Litólicos, que ocorrem devido à presença de diques de diabásio relacionados aos derrames basálticos da Formação Serra Geral. Para atingir este objetivo, investigamos a relação entre a declividade e a posição destes solos nas vertentes, a ocorrência de transporte de argila no interior destes perfis e sua eventual relação com a formação dos horizontes B níticos (Bni) e por fim, a relação da evolução destes sistemas pedológicos com a evolução do relevo regional. Os procedimentos adotados no estudo seguem a abordagem da Análise Estrutural da Cobertura Pedológica, proposta por Boulet (1982 a, b, c). Os resultados mostram que há uma relação entre declividade e a posição destes solos na vertente, embora não seja possível estabelecer um limite que possa ser extrapolado para toda a bacia do Pinguim. Revelam ainda indícios que apontam para processos de eluviação/iluviação nos perfis estudados e, por fim, que provavelmente os horizontes Bni se formaram a partir de antigos horizontes B latossólicos (Bw), como os encontrados no alto curso do ribeirão pinguim, e que há um processo atual de degradação dos horizontes Bni, que ocorre através da fragmentação de sua estrutura poliédrica em uma estrutura microagregada, sugerindo que há um processo de latossolização destes sistemas, que provavelmente evoluirão para uma cobertura pedológica semelhante à encontrada no setor do baixo curso do ribeirão Pinguim, dominado por Latossolos eutróficos. / This research investigated the genetic processes which give origin to the Red ferric Nitisols, trying to understand which factors lead to the differentiation between the typical Nitisols, with a horizon sequence A-Bni-C and the latosolic Nitisols, the most common type, with an A-Bni-Bw-C horizon sequence. The study area is the Miringuava Creek basin, located in the municipality of Maringá-PR, Brazil. This small hydrographic basin is placed in a sector of the Pinguim Creek basin, in which occurs a transition between two sectors dominated by Latosols, one in the high course of the Pinguim Creek and the other in the low course. The area is dominated by Nitisols and associations of shallow, poorly developed soils, which occur due to the presence of diabase dikes related to the basalts of the Serra Geral Formation. In order to accomplish the goal of this work, we investigated the relationship between slope and the positions of the soils in the hillslopes, clay transportation within the soil systems and finally, the relation between soil coverage and regional landform evolution. The procedures adopted for this research are based on the Structural Analisys of the Pedologic Coverage, proposed by Boulet (1982, a, b, c). The results show a relationship between slope and soil position, although it wasn´t possible to establish a limit which could be extrapolated for the entire area of the Pinguim Creek basin. The results also reveal evidence which point towards clay migration within the soil profiles studied in this work and finally, point to an evolution process in which the nitic horizons are formed from older latosolic horizons, such as the ones found in highest sectors of the Pinguim Creek basin, and that there is a present process of degradation of the nitic horizons, which through the fragmentation of the blocky structures into microgranular ones, suggesting that the Nitisols are evolving into younger eutrofic Latosols, similar to the ones found in the sectors of the low course of the Pinguim Creek.

[pt] O comportamento sísmico de taludes tem sido um tópico de grande interesse da engenharia geotécnica nos últimos 40 anos. Durante este período, a prática da engenharia nesta área evoluiu do emprego de técnicas elementares para procedimentos numéricos bastante complexos. A abordagem mais simples é a análise pseudo-estática na qual o carregamento do terremoto é simulado por uma aceleração horizontal estática equivalente atuando na massa de solo deslizante, utilizando-se um procedimento de equilíbrio limite (método das fatias), geralmente conservativo. O parâmetro que descreve o comportamento dinâmico do solo é referido como coeficiente sísmico k, e sua seleção depende fortemente da experiência e normas técnicas locais, porque não há maneira simples e segura de se escolher um valor adequado. O segundo procedimento é conhecido como método de Newmark, que envolve o cálculo de uma aceleração de escoamento, definida como a força inercial necessária para o fator de segurança atingir 1 em uma análise pseudo-estática pelo método de equilíbrio limite. O procedimento então usa os registros de aceleração do terremoto de projeto e o integra duplamente no tempo para calcular os deslocamentos permanentes acumulados. O terceiro método é referido como análise de Makdisi- Seed, que procura definir a estabilidade sísmica do talude em termos de deslocamentos aceitáveis em vez de um fator de segurança tradicional através de uma versão modificada do método de Newmark. Esta técnica apresenta uma maneira racional de calcular uma aceleração de escoamento média, necessária para produzir um valor do coeficiente de segurança do talude igual a 1. Gráficos específicos foram também desenvolvidos para estimativa dos deslocamentos permanentes, tendo sido bastante aplicados em aterros rodoviários, barragens e aterros sanitários. Finalmente, o mais sofisticado método para análise de estabilidade sísmica de taludes é conhecido como análise dinâmica, que normalmente incorpora modelos de elementos finitos e relações tensão x deformação complexas numa tentativa de obter melhores representações para o comportamento mecânico de taludes sob cargas cíclicas Os resultados destas análises podem incluir a história no tempo dos deslocamentos e tensões, bem como das freqüências naturais, efeitos de amortecimento, etc. Este trabalho apresenta uma comparação entre os métodos mencionados anteriormente, analisando o comportamento sísmico dos taludes da estrutura de contenção dos resíduos de lixiviação de minério de urânio, na Bahia, e dos taludes do bota-fora sul da mina de cobre Toquepala, situada no Peru. / [en] The seismic stability of slopes has been a topic of considerable interest in geotechnical engineering for the past 40 years. During that period, the state of practice has moved from simples techniques to more complicated numerical procedures. The simplest approach is the pseudo-static analysis in which the earthquake load is simulated by an equivalent static horizontal acceleration acting on the mass of the landslide, according to a generally conservative limit equilibrium analysis. The ground motion parameter used in a pseudo-static analysis is referred to as the seismic coefficient k, and its selection has relied heavily on engineering judgment and local code requirements because there is no simple method for determining an appropriate value. The second main procedure is known as the Newmark displacement analysis which involves the calculation of the yield acceleration, defined as the inertial force required to cause the static factor of safety to reach 1 from the traditional limit equilibrium slope stability analysis. The procedure then uses a design earthquake strong-motion record which is numerically integrated twice for the amplitude of the acceleration above the yield acceleration to calculate the cumulative displacements. These displacements are then evaluated in light of the slope material properties and the requirements of the proposed development. The third method is referred to as the Makdisi-Seed analysis sought to define seismic embankment stability in terms of acceptable deformation instead of conventional factors of safety, using a modified Newmark analysis. Their method presents a rational means to determine yield acceleration, or the average acceleration required to produce a factor of safety of unity. Design curves were developed to estimate the permanent earthquake- induced deformations of embankments, which have since been applied to sanitary landfill and highway embankments. Finally, the most sophisticated method for seismic slope stability calculations is known as the dynamic analysis, which normally incorporates a finite element model and a rather complex stress-strain behavior for geological materials in an attempt to obtain a better representation of the behavior of soils under cyclic loading. The results of the analysis can include a time history of displacements and stresses, as well as natural frequencies, effects of damping, etc. This work presents a comparison of the results obtained by the aforementioned approaches, considering the seismic behavior of the slopes of an uranium lixiviation pad situated in Bahia, Brazil, and the South embankment of the waste landfill of the Toquepala Mine, Peru.