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Lateral earth pressures (LEP) that arise due to backfill on retaining structures are typically determined by extending the principles of saturated soil mechanics. However, there is evidence in the literature to highlight the LEP on retaining structures due to the influence of soil backfill in saturated and unsaturated conditions are significantly different. Some studies are reported in the literature to interpret the variation of LEP on the retaining structures assuming that the variation of matric suction in unsaturated backfill material is hydrostatic (i.e. matric suction is assumed to decrease linearly from the surface to a value of zero at the ground water table). Such an assumption however is not reliable when the backfill behind the retaining wall is an expansive soil, which is extremely sensitive to the changes in variation of water content values. Significant volume changes occur in expansive soils due to the influence of environmental factors such as the infiltration and evaporation. In addition to the volume changes, the swelling pressure of the expansive soils also varies with changes in water content and can significantly influence the LEPs behind the retaining wall. In this thesis, a framework for estimating the LEPs of unsaturated soils is proposed considering the variation of matric suction with respect to various water flow rates (i.e. infiltration and evaporation). The proposed approach is extended for expansive and non-expansive soils in this thesis taking into account of the influence of both the cracks and the lateral swelling pressure with changes in water content. A program code LEENES (Lateral pressure estimation on retaining walls taking account of Environmental factors for Expansive and Non-Expansive Soils) in MATLAB is written to predict the LEP. The program LEENES is valuable tool for geotechnical engineers to estimate the LEPs on retaining structures for various scenarios that are conventionally encountered in geotechnical engineering practice. The studies presented in this thesis are of interest to the practitioners who routinely design retaining walls with both expansive and non-expansive soils as backfill material.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Concrete water retaining structures (WRS) in South Africa are under scrutiny due to the numerous durability problems that they have experienced lately; despite the efforts by local and national authorities in conserving these structures. At the heart of these problems are the creep and shrinkage phenomena. While shrinkage is the reduction of concrete volume with time, creep is defined as the time-dependent increase of concrete strain under constant or controlled stress. Both phenomena are affected by conditions to which WRS are exposed hence their accurate prediction is required. Numerical models have been developed to calculate the extent to which concrete creeps or shrinks over time. The objective of this thesis is to identify which of these models is better equipped to be used in South African WRS design. This is achieved through a systematic method that involves an investigation into the contents of these models and a statistical comparison of model calculations to WRS representative data. In partnership with reputable universities, a pioneer experimental creep and shrinkage data base is created in this project from which the WRS related data is selected. While investigating the contents of the numerical models, their applicability to South African WRS is identified and the integrity of model contents is assessed. Indeed, a few irregularities are found in the process and are presented in this thesis. The model calculations are statistically compared to data in the form of individual experiments as well as in the form of groups of experiments with similar concretes to find the ideal prediction model for different types of concretes as well. Also pioneered in this project is a weighted criteria and point system in which the findings of the model content assessment and statistical evaluations are incorporated. It is based on this system that conclusions are drawn and the most suitable prediction model for WRS design in South Africa is selected.

Este trabalho apresenta a construção e instrumentação de uma estrutura de contenção reforçada com geotêxtil, com 4,0 m de altura, construída na cidade de Nova Odessa-SP. A instrumentação consistiu em medir os deslocamentos horizontais e verticais com barras de aço e placas magnéticas, respectivamente. Além disso, foram realizadas simulações numéricas para comparar os resultados medidos e simulados do protótipo e avaliar o comportamento da estrutura para alguns tipos de solo, rigidez da inclusão e arranjos das inclusões. Pode-se concluir que os resultados medidos e simulados estão concordantes. Através das análises paramétricas concluiu-se que aumentando-se a rigidez do solo reduz-se os deslocamentos horizontais da estrutura. Com o aumento na rigidez da inclusão obtém-se menores deslocamentos, no entanto, em solos muito rígidos esta redução é pouco significativa. As estruturas com maior número de reforços reduzem as tensões em cada inclusão e diminuem os deslocamentos horizontais da estrutura. As forças de tração máximas, mobilizadas nas inclusões, são maiores para solos menos rígidos. Alguns resultados de obras instrumentadas, encontrados na literatura, são apresentados e comparados com os medidos e simulados. Destas comparações concluiu-se que o tipo de solo é o fator que mais influencia no desempenho de estruturas de contenção reforçadas com geossintéticos / This work presents the construction and instrumentation of a geotextile reinforced retaining structure, with 4,0 m height, built in the city of Nova Odessa-SP. The instrumentation consisted of measuring the horizontal and vertical displacements with steel bars and magnetic plates, respectively. Numeric simulations were accomplished to compare the measured and simulated results of the prototype and to evaluate the behavior of the structure for some soil types, reinforcement rigidity and different reinforcement layout. It was concluded that the measured and simulated results are in good agreement. The parametric analyses showed that the amount of horizontal displacements of the structure are reduced when the rigidity of the soil increases. Although smaller displacements are obtained when the rigidity of the inclusion is increased, in very rigid soils this reduction is not very significant. Structures with larger number of reinforcements reduce the stresses in each inclusion, decreasing the horizontal displacements of the structure. The maximum tensile forces mobilized in the inclusions, are larger for less rigid soils. Some case record results documented in the literature are presented and compared with the measured and simulated results obtained in this work. These comparisons allowed to conclude that the soil type is the most relevant factor in the performance of reinforced retaining structure with geosynthetics

Este trabalho apresenta a construção e instrumentação de uma estrutura de contenção reforçada com geotêxtil, com 4,0 m de altura, construída na cidade de Nova Odessa-SP. A instrumentação consistiu em medir os deslocamentos horizontais e verticais com barras de aço e placas magnéticas, respectivamente. Além disso, foram realizadas simulações numéricas para comparar os resultados medidos e simulados do protótipo e avaliar o comportamento da estrutura para alguns tipos de solo, rigidez da inclusão e arranjos das inclusões. Pode-se concluir que os resultados medidos e simulados estão concordantes. Através das análises paramétricas concluiu-se que aumentando-se a rigidez do solo reduz-se os deslocamentos horizontais da estrutura. Com o aumento na rigidez da inclusão obtém-se menores deslocamentos, no entanto, em solos muito rígidos esta redução é pouco significativa. As estruturas com maior número de reforços reduzem as tensões em cada inclusão e diminuem os deslocamentos horizontais da estrutura. As forças de tração máximas, mobilizadas nas inclusões, são maiores para solos menos rígidos. Alguns resultados de obras instrumentadas, encontrados na literatura, são apresentados e comparados com os medidos e simulados. Destas comparações concluiu-se que o tipo de solo é o fator que mais influencia no desempenho de estruturas de contenção reforçadas com geossintéticos / This work presents the construction and instrumentation of a geotextile reinforced retaining structure, with 4,0 m height, built in the city of Nova Odessa-SP. The instrumentation consisted of measuring the horizontal and vertical displacements with steel bars and magnetic plates, respectively. Numeric simulations were accomplished to compare the measured and simulated results of the prototype and to evaluate the behavior of the structure for some soil types, reinforcement rigidity and different reinforcement layout. It was concluded that the measured and simulated results are in good agreement. The parametric analyses showed that the amount of horizontal displacements of the structure are reduced when the rigidity of the soil increases. Although smaller displacements are obtained when the rigidity of the inclusion is increased, in very rigid soils this reduction is not very significant. Structures with larger number of reinforcements reduce the stresses in each inclusion, decreasing the horizontal displacements of the structure. The maximum tensile forces mobilized in the inclusions, are larger for less rigid soils. Some case record results documented in the literature are presented and compared with the measured and simulated results obtained in this work. These comparisons allowed to conclude that the soil type is the most relevant factor in the performance of reinforced retaining structure with geosynthetics

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Water-retaining structures are commonly used in South Africa for the storage of potable water and waste water. However, a South African code pertaining to the design of concrete water-retaining structures do not currently exist and therefore use is made of the British Standard BS 8007 (1987). For the design of concrete water-retaining structures in South Africa, only the hydrostatic loads are considered while forces due to seismic activity are often neglected even though seismic excitations of moderate magnitude occur within some regions of the country. Hence, the primary aim of this study was to determine whether seismic activity, as it occurs in South Africa, has a significant influence on water-retaining structures and whether it should be considered as a critical load case. In order to assess the influence of seismic activity on the design of water-retaining structures the internal forces in the wall and the required area of reinforcement were compared. Comparisons were made between the seismic analyses and static analyses for both the ultimate and serviceability limit states. In order to obtain the internal forces in the wall use was made of an appropriate Finite element model. Three Finite element models were investigated in this study and the accuracy of each model was assessed based on the fundamental frequency, base shear force and overturning moment. These values were compared to the values obtained with the numerical method presented by Veletsos (1997) which was verified with Eurocode 8: Part 4 (2006). The results obtained indicated that seismic excitations of moderate magnitude do have a significant influence on the reinforcement required in concrete water-retaining structures. For both the ultimate limit state and serviceability limit state the required reinforcement increased significantly when seismic loads were considered in the design. As in the case for static design of water-retaining structures, the serviceability limit state also dominated the design of these structures under seismic loading. / AFRIKAANSE OPSOMMING: Beton waterhoudende strukture in Suid-Afrika word op ‘n gereelde basis gebruik vir die stoor van drink- sowel as afvalwater. ‘n Suid-Afrikaanse kode vir die ontwerp van hierdie strukture bestaan egter nie en dus word die Britse kode BS 8007 (1987) hiervoor gebruik. Vir ontwerp doeleindes word soms slegs die hidrostatiese kragte beskou terwyl kragte as gevolg van seismiese aktiwiteite nie noodwendig in berekening gebring word nie. Seismiese aktiwiteite van gematigde grootte kom egter wel voor in sekere dele van Suid-Afrika. Die hoofdoel van hierdie studie was dus om die invloed van seismiese aktiwiteite, soos voorgeskryf vir Suid-Afrikaanse toestande, op beton waterhoudende strukture te evalueer asook om te bepaal of dit ‘n kritiese lasgevalle sal wees. Vir hierdie doel is die interne kragte asook die area staal bewapening vir elk van die statiese en dinamiese lasgevalle vergelyk. Vergelykings is getref tussen die dinamiese en statiese resultate vir beide die swigtoestand en die diensbaarheidstoestand. Vir die bepaling van die interne kragte is gebruik gemaak van eindige element modelle. Tydens hierdie studie was drie eindige element modelle ondersoek en die akkuraatheid van elk geëvalueer op grond van die fundamentele frekwensie, die fondasie skuifkrag en die omkeermoment. Hierdie waardes was ondermeer bereken met twee numeriese metodes soos uiteengesit in Veletsos (1997) en Eurocode 8: Part 4 (2006). Die resultate dui daarop dat die invloed van seismiese aktiwiteite op beton waterhoudende strukture in Suid-Afrika nie weglaatbaar klein is nie en wel in berekening gebring behoort te word tydens die ontwerp. Die interne kragte vir beide die swigtoestand en diensbaarheidstoestand is aansienlik hoër vir die seismiese lasgeval as vir die statiese geval. Die diensbaarheidstoestand het deurentyd die ontwerp van beton waterhoudende strukture vir seismiese toestande oorheers.

Thesis (MScEng)--Stellenbosch University, 2013. / Durability and impermeability in a water-retaining structure are of prime importance if the structure is to fulfill its function over its design life. In addition, serviceability cracking tends to govern the design of water retaining structures. This research concentrates on load-induced cracking specifically that due to pure bending and to direct tension in South African reinforced concrete water retaining structures (WRS). As a South African design code for WRS does not exist at present, South African designers tend to use the British codes in the design of reinforced concrete water-retaining structures. However, with the release of the Eurocodes, the British codes have been withdrawn, creating the need for a South African code of practice for water-retaining structures. In updating the South African structural design codes, there is a move towards adopting the Eurocodes so that the South African design codes are compatible with their Eurocode counterparts. The Eurocode crack model to EN1992 (2004) was examined and compared to the corresponding British standard, BS8007 (1989). A reliability study was undertaken as the performance of the EN1992 crack model applied to South African conditions is not known. The issues of the influence of the crack width limit and model uncertainty were identified as being of importance in the reliability crack model.

[pt] O projeto de estruturas de contenção de solos submetidas a carregamentos dinâmicos é um importante tema da engenharia geotécnica, principalmente nos países andinos. A abordagem mais comum consiste no emprego de métodos de equilíbrio limite (pseudo-estáticos) ou de técnicas baseadas na formulação de Newmark (1965) para cálculo de deslocamentos permanentes da estrutura. Um método pseudo-estático clássico é o apresentado por Mononobe-Okabe (1929) como uma extensão da teoria de Coulomb (1773), enquanto que Richards e Elms (1979) sugeriram um método de projeto baseado em deslocamentos permanentes. Nesta dissertação os resultados da aplicação do método dos elementos finitos na análise dinâmica do comportamento de um muro de gravidade são comparados com aqueles previstos por diversos outros métodos analíticos propostos na literatura, tanto em termos do cálculo de empuxos quanto de deslocamentos permanentes. As vantagens e limitações destes métodos são discutidas, bem como são discutidos vários aspectos da modelagem numérica que devem ser cuidadosamente considerados pelo engenheiro geotécnico para obter uma simulação representativa do problema dinâmico. / [en] The design of earth retaining structures during earthquakes is an important subject of the geotechnical engineering, mainly in the Andesian countries of South America. The most common approach consists in the use of some quasi-static method or technique based on Newmark s (1965) model to estimate inelastic displacements of the structure. The classical quasi-static method is the one proposed by Mononobe -Okabe (1926, 1929), as an extension of the Coulomb s (1773) theory to a dynamic context, while Richards and Elms (1979) suggested a design method based on inelastic displacements. In this thesis the dynamic response of a gravity retaining wall obtained through the finite element method are compared with those predicted by several other analytical formulation proposed in the literature, concerning both the resultant of the earth pressures and the wall displacements experienced during the earthquake. The advantages and shortcomings in the application of all these methods are discussed herein, as well as several modeling aspects are discussed that must be carefully considered by the geotechnical engineer in order to obtain a representative simulation of the dynamical problem.

Orientador: Mauro Augusto Demarzo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-07T08:31:00Z (GMT). No. of bitstreams: 1 Tacitano_Marcelo_D.pdf: 8426940 bytes, checksum: 2052cac2233a599ef85b5133ca5ceec4 (MD5) Previous issue date: 2006 / Resumo: As estruturas de contenção de valas, normalmente de madeira, aço ou concreto, podem ser constituídas por estacas-prancha, estacas com pranchões, estacões, paredes-diafragma entre outras e precisam ser dimensionadas, de que maneira que atinjam adequadamente os requisitos de funcionalidade, exeqüibilidade, segurança e economia a que se propõem. Dentre os métodos para o seu dimensionamento é possível enquadrá-los em três grandes grupos. Os Métodos Empíricos que se baseiam em resultados de medidas experimentais, os Métodos Semi-Empíricos que admitem como carregamento um diagrama de pressões para ambos os lados da parede, em cada fase de escavação, pressupondo o tipo de grandeza dos deslocamentos e considerando as estroncas e tirantes como apoios fixos e, finalmente, os Métodos Analíticos, que levam em conta as características de resistência e rigidez da estrutura e do maciço e possibilitam o cálculo evolutivo em que os esforços e deslocamentos das fases anteriores são efetivamente levados em conta nos cálculos das fases seguintes. Inicialmente uma ampla revisão bibliográfica sobre os métodos de cálculo de paredes de contenções é apresentada. Após, este trabalho adota como foco de estudo o Modelo de Winkler, através de Método Analítico Unidimensional, que tem sua aplicação prática pela construção do programa CEDEVE (Cálculo Evolutivo de Deslocamentos e Esforços em Valas Escoradas). Este método assimila a parede como uma viga de largura unitária, sendo o solo modelado como molas de comportamento elasto-plástico perfeito incluindo histerese. Estroncas e tirantes, de comportamento elástico, com ou sem esforços iniciais, podem ser introduzidos na estrutura. As ações sobre a estrutura advêm dos empuxos de solo, de água e das eventuais sobrecargas presentes na superfície. Os cálculos são conduzidos de acordo com as fases de escavação, retirando-se as ações (empuxos) e molas correspondentes ao solo escavado e introduzindo-se as estroncas e/ou tirantes a serem instalados, sendo que os esforços e deslocamentos ocorridos nas fases anteriores são devidamente considerados nos cálculos das fases seguintes. O reaterro, quando existir, também é considerado. Um diferencial importante do método de cálculo proposto com relação a outros similares é a possibilidade da inclusão dos efeitos de temperatura nos cálculos dos deslocamentos e esforços, sendo que tais efeitos térmicos podem ser considerados sobre as estroncas, o que promove a tendência de seu alongamento, que sendo parcialmente impedido, gera conseqüentes esforços de compressão e também na própria parede de contenção através de gradientes que induzem flexão, e, portanto também influindo nos esforços sobre o sistema de estroncas. Um estudo prático e numérico é conduzido com o intuito de se validar e verificar o programa CEDEVE, primeiramente testando seus resultados com o programa SAP 2000 e, após, comparando os resultados por ele gerados com vários outros programas disponíveis (SPW2003, DEEP e ESTWIN). O efeito da temperatura sobre as estroncas, calculado pelo CEDEVE, é comparado com alguns resultados de instrumentações disponíveis na bibliografia consultada. Além disso, um estudo comparativo com alguns Métodos Empíricos e Semi-Empíricos é conduzido. De uma forma geral, é possível concluir que o Modelo de Winkler utilizado na modelagem do problema gera resultados satisfatórios e sua relação custo benefício é bastante atraente na análise de paredes de contenção / Abstract: The retaining structures, usually of wood, steel or concrete, can be constituted by sheet pile wall, piles with lagging, ¿in cast¿ pile walls and diaphragm walls among others and need to be designed, so that they reach the requirements about functionality, execution, safety and economy an appropriate way. It is possible divide the design methods in three great groups. The Empirical Methods that has been based on results of experimental measures, the Semi-Empirical Methods that admit as loading a diagram of earth pressures for both sides of the wall, in each excavation phase, presupposing the displacements and considering the struts and anchorage as fixed supports and, finally, the Analytical Methods that take into account the characteristics of strength and stiffness of the structure and soil and they make possible the evolutionary calculation of internal efforts (strut forces, bending moments and shear forces) as well as the displacements, so the previous phases are taken indeed into account in the calculations of the following phases. Initially a wide bibliographical revision on the methods of calculation of retaining structures is presented. After that, this work adopts as focus the Winkler¿s Model, through One-Dimensional Analytical Method that bases the development of the CEDEVE program (Evolutionary Calculation of Displacements and Efforts in Braced Trenches). This program assimilates the wall as a beam of unitary width, being the soil modeled as springs with linear perfectly elastic-plastic behavior including histeresis. Struts and anchorages, of elastic behavior, with or without initials forces, can be introduced in the structure. The actions on the structure occur by the soil pressures, water pressures and eventually overloads in the soil surface. The calculations are performed in agreement with the excavation phases, leaving the actions (soil pressures) and springs corresponding to the dug soil as well as introducing the struts/anchorages, so that the efforts and displacements happened in the previous phases are properly considered in the calculations of the following phases. The process of cover the trench with earth, when it exists, is also considered. A important differential of the CEDEVE program regarding other similar ones is the possibility of the inclusion of the temperature effects in the calculations of the displacements and efforts, and such thermal effects can be considered on the struts, what promotes the tendency of its stretch, that being impeded partially, generates consequent compression and also in the own retaining wall through gradients that induce bending and, therefore, also influencing on the loads on the struts system. A practical and numerical study is done with the intention of validate and verify the CEDEVE program, firstly testing their results with the program SAP 2000 and, after that, comparing the results generated with several other available programs (SPW2003, DEEP and ESTWIN). The effect of the temperature on the struts, calculated by CEDEVE, is compared with some results of available instrumentations in the consulted bibliography. Besides this, a comparative study with some Empirical and Semi-Empirical Methods was done. In general, it is possible to conclude that the Winkler¿s Model used in the modeling of the problem generates satisfactory results and its relationship cost benefit is quite attractive in the analysis of retaining structures / Doutorado / Estruturas / Mestre em Engenharia Civil

Design of retaining structures depends upon the load which is transferred from backfill soil as well as external loads and also the resisting capacity of the structure. The traditional safety factor approach of the design of retaining structures does not address the variability of soils and loads. The properties of backfill soil are inherently variable and influence the design decisions considerably. A rational procedure for the design of retaining structures needs to explicitly consider variability, as they may cause significant changes in the performance and stability assessment. Reliability based design enables identification and separation of different variabilities in loading and resistance and recommends reliability indices to ensure the margin of safety based on probability theory. Detailed studies in this area are limited and the work presented in the dissertation on the Optimum design of retaining structures under static and seismic conditions: A reliability based approach is an attempt in this direction. This thesis contains ten chapters including Chapter 1 which provides a general introduction regarding the contents of the thesis and Chapter 2 presents a detailed review of literature regarding static and seismic design of retaining structures and highlights the importance of consideration of variability in the optimum design and leads to scope of the investigation. Targeted stability is formulated as optimization problem in the framework of target reliability based design optimization (TRBDO) and presented in Chapter 3. In Chapter 4, TRBDO approach for cantilever sheet pile walls and anchored cantilever sheet pile walls penetrating sandy and clayey soils is developed. Design penetration depth and section modulus for the various anchor pulls are obtained considering the failure criteria (rotational, sliding, and flexural failure modes) as well as variability in the back fill soil properties, soil-steel pile interface friction angle, depth of the water table, total depth of embedment, yield strength of steel, section modulus of sheet pile and anchor pull. The stability of reinforced concrete gravity, cantilever and L-shaped retaining walls in static conditions is examined in the context of reliability based design optimization and results are presented in Chapter 5 considering failure modes viz. overturning, sliding, eccentricity, bearing, shear and moment failures in the base slab and stem of wall. Optimum wall proportions are proposed for different coefficients of variation of friction angle of the backfill soil and cohesion of the foundation soil corresponding to different values of component as well as lower bounds of system reliability indices. Chapter 6 presents an approach to obtain seismic passive resistance behind gravity walls using composite curved rupture surface considering limit equilibrium method of analysis with the pseudo-dynamic approach. The study is extended to obtain the rotational and sliding displacements of gravity retaining walls under passive condition when subjected to sinusoidal nature of earthquake loading. Chapter 7 focuses on the reliability based design of gravity retaining wall when subjected to passive condition during earthquakes. Reliability analysis is performed for two modes of failure namely rotation of the wall about its heel and sliding of the wall on its base are considering variabilities associated with characteristics of earthquake ground motions, geometric proportions of wall, backfill soil and foundation soil properties. The studies reported in Chapter 8 and Chapter 9 present a method to evaluate reliability for external as well as internal stability of reinforced soil structures (RSS) using reliability based design optimization in the framework of pseudo static and pseudo dynamic methods respectively. The optimum length of reinforcement needed to maintain the stability against four modes of failure (sliding, overturning, eccentricity and bearing) by taking into account the variabilities associated with the properties of reinforced backfill, retained backfill, foundation soil, tensile strength and length of the geosynthetic reinforcement by targeting various component and system reliability indices is computed. Finally, Chapter 10 contains the important conclusions, along with scope for further work in the area. It is hoped that the methodology and conclusions presented in this study will be beneficial to the geotechnical engineering community in particular and society as a whole.