The mechanism of soil-reinforcement interaction for a reinforced embankment on soft clay has been explored by conducting a parametric study using a coupled non-linear elastoplastic finite element program. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. Previous research using geotechnical centrifuge modelling and present research using finite element modelling has confirmed that the tension mobilized in the reinforcement is only of the order of active lateral thrust in the embankment. The parametric study has revealed that the soil-reinforcement interaction mechanism depends on the ratio of embankment height to the depth of the clay layer. The embankment behaves similar to a rigid footing in case of deep clay deposit. In this case, the failure mechanism is similar to a slip circle and there is very little contribution from the clay-reinforcement interface towards the mobilization of reinforcement tension. However, if the depth of clay deposit is small, the soil-reinforcement interaction mode is similar to direct shear failure and slip surface is located close to the clay-reinforcement interface. In this case, the contribution of clay-reinforcement interface towards the tension mobilized in the reinforcement is higher and therefore, the contribution of the reinforcement towards overall stability of the embankment is greater. Based on the results of the parametric study a novel serviceability criterion is proposed that aims to limit the lateral deformation of the clay foundation at the toe of the embankment by limiting the allowable mobilized tension in the reinforcement. A simple procedure for the evaluation of the efficiency of soil-reinforcement interface for reinforced embankments on soft clays is also proposed. The validity of the proposed serviceability criterion and the design charts was successfully tested using two field case studies. Sackville test embankment constructed to failure in 1989 and a levee test section that remained serviceable after construction in 1987 at Plaquemine, Louisiana were able to confirm the validity of the serviceability criterion proposed in the present study.

The mechanism of soil-reinforcement interaction for a reinforced embankment on soft clay has been explored by conducting a parametric study using a coupled non-linear elastoplastic finite element program. One of the major issues in the design of a reinforced embankment on soft clay is the magnitude of tension that can be mobilized in the geosynthetic reinforcement. Previous research using geotechnical centrifuge modelling and present research using finite element modelling has confirmed that the tension mobilized in the reinforcement is only of the order of active lateral thrust in the embankment. The parametric study has revealed that the soil-reinforcement interaction mechanism depends on the ratio of embankment height to the depth of the clay layer. The embankment behaves similar to a rigid footing in case of deep clay deposit. In this case, the failure mechanism is similar to a slip circle and there is very little contribution from the clay-reinforcement interface towards the mobilization of reinforcement tension. However, if the depth of clay deposit is small, the soil-reinforcement interaction mode is similar to direct shear failure and slip surface is located close to the clay-reinforcement interface. In this case, the contribution of clay-reinforcement interface towards the tension mobilized in the reinforcement is higher and therefore, the contribution of the reinforcement towards overall stability of the embankment is greater. Based on the results of the parametric study a novel serviceability criterion is proposed that aims to limit the lateral deformation of the clay foundation at the toe of the embankment by limiting the allowable mobilized tension in the reinforcement. A simple procedure for the evaluation of the efficiency of soil-reinforcement interface for reinforced embankments on soft clays is also proposed. The validity of the proposed serviceability criterion and the design charts was successfully tested using two field case studies. Sackville test embankment constructed to failure in 1989 and a levee test section that remained serviceable after construction in 1987 at Plaquemine, Louisiana were able to confirm the validity of the serviceability criterion proposed in the present study.

Consolidation theory states that decreasing the spacing of prefabricated vertical drains will decrease the time required to achieve primary consolidation. Previous field tests have shown that there exists a "critical" drain spacing, which is the point at which further spacing decrease does not decrease the time of primary consolidation. This "critical" spacing is thought to be due to disturbance effects from installation of the drains. Previous studies have found that the "critical" drain spacing may be dependent upon soil layering and drain and mandrel dimensions. Thin, interbedded clay layers have been found to be affected greatly due to the smear zone, while few tests have been conducted to determine the validity for thick bedded clays. Currently two design and analysis methods are in existence, neither of which is standardized. The two methods are the modeling of the smear zone, which requires knowledge of soil parameters within that zone, and the modeling using a back-calculated Ch/Cv ratio.In order to evaluate the validity of these design methods and to obtain more data that can be used in determining the relationship between anchor type, drain spacing, and soil profile, full-scale field tests were conducted at Mountain View Corridor in Lehi, Utah. These field tests were performed along a test section that was divided into sections containing 5.8, 5.0, 4.0 and 3.0 ft triangular spacings and rebar or plate anchors. By using the smear zone model, with a Ch/Cv ratio of 1.25 and ds of 3.07 times dm, the time rate of settlement was able to be predicted reasonably well, while using the back-calculated Ch/Cv ratio, with no smear zone, also predicted the time rate reasonably well. From the testing, it was found that the thick clay profile can facilitate closer spacings than a thin clay profile. Also, it was found that the rebar anchor type causes about twice the disturbance of the plate anchor. The results helped validate the existing models and show that the effectiveness of the drains is dependent upon drain spacing, soil profile, and anchor type

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-10-01T17:39:29Z No. of bitstreams: 1 ANTONIO CRISTINO DA CONCEIÇÃO - DISSERTAÇÃO PPGECA 1977..pdf: 27409984 bytes, checksum: 5912f51eef9d8359747739e237cf1e66 (MD5) / Made available in DSpace on 2018-10-01T17:39:29Z (GMT). No. of bitstreams: 1 ANTONIO CRISTINO DA CONCEIÇÃO - DISSERTAÇÃO PPGECA 1977..pdf: 27409984 bytes, checksum: 5912f51eef9d8359747739e237cf1e66 (MD5) Previous issue date: 1977-07 / Este praqalho, trata do estudo dos parâmetros de resistência e consolidação de uma argila mole que faz parte do subsolo da cidade de João Pessoa. Da literatura consultada, apresentam-se dados e conclusões de estudos realizados em outras regiões, relacionados com o presente trabalho, onde destacamos principalmente os fatores fundamentais que influenciam sobre a resistência ao cisalhamento e a compressibilidade do solos argiloso. presenta-se uma pequena descrição dos aspectos geológicos do subsolo da região em estudo. Em uma camada de 12.00 metros de espessura, foram colhidas amostras do subsolo a cada metro de profundidade pelo uso de tubos de paredes finas tipo Shelby. Os ensaios de laboratório consistiram de: ensaio de caracterização do solo, ensaio de palheta (Vane Test), consolidação, compressão não confinada, triaxial não consolidado não drenado e consolidado drenado. As avaliações de resistência no campo, foram efetuadas através de três tipos de ensaios: ensaio de palheta (Vane Test), penetrõmetro estático (Deep Sounding) e o penetrômetro dinâmico (SPT). O solo é caracterizado como uma argila siltosa, apresentando alta plasticidade e compressibilidade. 0 estudo mostra ainda, que a argila apresenta um pequeno aumento da resistência ao cisalhamento ao longo da profundidade. A argila exibe baixa permeabilidade. Utilizou-se o processo estatístico de regressão linear, para analisar possíveis correlações entre os parâmetros encontrados in situ e no laboratório. Esta análise mostra que dentro das limitações do estudo, existem boas correlações entre alguns parâmetros determinados. / his research studies the strength and consolidation parameters of a soft clay that forms part of the subsoil of the city of João Pessoa. From the literature consulted those topics which have direct bearing on this study were presented, the funda mental factors which influence the shear strength and the compressibility of this soil were elaborated. The geological aspects of the sub soil are described briefly. From a soil layer of 12.00 m thickness samples were collected from each meter of depth using thinwalled Shelby tubes. The laboratory tests consisted of: vane shear, consolidation , unconfined compression, unconsolidated undrained and Consolidated drained triaxial tests, soil classification tests were also performed. In the field: vane shear, static ánd dynamic penetrometer tests were carried out. The soil was classified as a silty clay, having a high plasticity and compressibi1ity. The 1ow shear strength increased slightly with depth. The clay exhibited a low permeability.

[pt] Um amplo trabalho de pesquisa, envolvendo extensivas investigações de campo e laboratório de um depósito de argila mole localizado na Zona Industrial de Santa Cruz, Rio de Janeiro, RJ, vem sendo desenvolvido pela PUC-Rio desde meados de 2005. Evidências de recalques em estruturas construídas nessa região têm sido reportadas desde o final da década de 70. O presente trabalho apresenta resultados de estudos de laboratório realizados visando à caracterização do depósito argiloso e a determinação de seus parâmetros de compressibilidade e adensamento. Para tanto, desenvolveu- se um programa experimental compreendendo a caracterização físico-químico- mineralógica de amostras do perfil e a execução de ensaios de adensamento edométrico e triaxial hidrostático e anisotrópico. Os experimentos em células edométricas envolveram ensaios convencionais, com medida de permeabilidade e com determinação de compressão secundária. Aspectos de qualidade das amostras ensaiadas são discutidos. Os resultados obtidos propiciaram uma estimativa do K0 do material normalmente adensado, um entendimento do estágio de adensamento hoje existente e uma estimativa preliminar de recalques que podem ainda vir a ocorrer sob as presentes condições de carregamento. / [en] A large research work comprising extensive field and laboratory investigations on a soft clay deposit located in the Industrial Zone of Santa Cruz, Rio de Janeiro, RJ, is being developed at PUC-Rio since 2005. Occurrences of settlement of structures built in this region have been reported since the end of the decade of 1970. This work presents results of laboratory studies aiming at the characterization of the soft clay deposit and the determination of compressibility and consolidation parameters of the clay. The experimental program developed comprised physical-chemical- mineralogical characterization of samples from the soil profile and the execution of oedometric consolidation tests and hydrostatic and anisotropic triaxial tests. The experiments in oedometric cells comprised conventional tests and tests with measurement of permeability and determination of secondary compression. Aspects of quality of the samples are highlighted. The obtained results propitiated an estimation of the K0 of the normally consolidated material, an understanding of the present stage of consolidation of the deposit and a preliminary assessment of settlements that may still occur in the site under the present loading conditions.

[pt] A caracterização geotécnica de um depósito de argila mole da Baixada Fluminense foi realizada neste trabalho. Sobre o depósito, foi executado um extenso aterro para implantação da Indústria Rio Polímeros, abrangendo aproximadamente 500.000m2. Uma ampla campanha de ensaios de laboratório foi realizada em amostras extraídas da camada de argila mole, antes do lançamento do aterro. Este programa de investigação incluiu ensaios de caracterização, ensaios de adensamento convencionais (SIC) e contínuos (CRS) e ensaios triaxiais drenados e não drenados. Os ensaios CRS foram realizados sob diferentes velocidades de deformação, a fim de avaliar a sua influência nas características de compressibilidade e de adensamento do material. Foi também realizado um ensaio CRS em amostra previamente amolgada. Os parâmetros geotécnicos obtidos foram confrontados e mostraram-se razoavelmente concordantes com os valores reportados na literatura, para a Baixada Fluminense. A influência da velocidade de deformação dos ensaios CRS foi significativa. Entretanto, para a faixa de velocidades adotada no presente trabalho, os parâmetros resultantes situaram-se dentro da dispersão observada na área. O amolgamento prévio da amostra resultou numa redução dos parâmetros de compressibilidade e de adensamento. / [en] This work has focused on the geotechnical characterization of a soft clay deposit in Baixada Fluminense, Rio de Janeiro. In this area, a large embankment of approximately 500.000m2 was executed for implantation of Rio Polimeros Industry. An extensive laboratory program was carried out on undisturbed samples, extracted from the soft clay layer before embankment construction. The geotechnical investigation consisted of characterization tests, conventional (SIC) and controlled deformation (CRS) consolidation tests, and drained and undrained triaxial tests. CRS tests were carried out under different deformation velocities, in order to evaluate its influence on compressibility parameters and on consolidation rates. An additional CRS test was also performed using a disturbed sample. The geotechnical parameters were analysed and revealed a resonable agreement with the results reported in the literature, for the Baixada Fluminense soft clay deposit. The strain rate of CRS tests has a significant influence on compressibility parameters. However, the results still remain within the range of experimental data, avaliable for the soft clay deposit of Baixada Fluminense. It is worthwile to notice that a limited range of velocities was used in this research. The sample disturbance resulted in a reduction of both compressibility parameters (cr, cc) and coefficient of consolidation.

Stone column technique is mostly used to reinforce soft cohesive soils. Settlements are decreased under foundations and bearing capacity is increased. This study initially focuses on a comprehensive review of literature about stone column reinforced soils. Afterwards, numerical modeling of stone column reinforced soft clays is done. Three different cases are chosen on different foundation soils mainly soft clays. Parametric studies are done to determine influence of parameters on settlement reduction ratio under three different foundation conditions. Analyses are converted to two dimensional conditions and this conversion is also compared within the scope of this study. Settlement reduction ratio response to variation in parameters revealed similar results under three different foundation conditions.

[pt] Este trabalho apresenta os resultados de uma investigação sobre as características geotécnicas do depósito de argila mole da enseada do Cabrito em Salvador-Bahia. Nesta área está em curso a implantação de uma obra de urbanização, visando o assentamento de famílias que habitavam anteriormente no local, em casas construídas sobre palafitas. A determinação das propriedades geotécnicas do solo foi feita através de ensaios de campo e de laboratório. No campo, foram realizados ensaios de piezocone e de dissipação de poro-pressão, além de sondagens com medida de SPT e ensaios de palheta. Para a realização dos ensaios de dissipação de poropressões in situ, foi desenvolvida uma sonda piezométrica, que está apresentada neste trabalho. No laboratório, o programa experimental constou de ensaios de caracterização, triaxiais e de adensamento (incrementais e contínuos). Para os ensaios de adensamento contínuos, foram realizadas algumas modificações no equipamento convencional, que também são descritas neste trabalho. / [en] This work presents and discusses the geotechnical characteristics of the Cabrito's inlet soft clay in Salvador-Bahia. On this area is in course the implantation of an embankment, seeking to locate families that inhabited previously in the place, in houses built on wood piles. The determination of the soil properties was made through geotechnical tests of field and laboratory. For the accomplishment of the tests of dissipation of poropressure in situ, a piezometer probe was developed, that is presented in this work. For the continuos oedometer tests, some modifications were accomplished in a conventional cell, that are also presented in this volume. Finally, the obtained results of physical , of consolidation, of deformation and of resistance characteristics, are analyzed together, in such a way to obtain a better characterization of the properties of the deposit.

[pt] No presente trabalho é realizado um estudo experimental das características de compressibilidade e adensamento de argilas moles. Foram realizados ensaios convencionais de adensamento (SIC) e ensaios de adensamento com velocidade constante de deformação (CRS) - em diferentes velocidades - ensaios de adensamento com uma face drenante e ensaios traxiais. As amostras foram remoldadas em laboratório, a partir de uma mistura de bentonita e caulim, na proporção de 98 : 2 em peso, e adensadas istoropicamente, a fim de se garantir uma melhor qualidade quanto à homogeneidade e isotropia do material. Os resultados são obtidos e analisados através das curvas típicas para os ensaios de adensamento. São obtidos os valores dos parâmetros de compressibilidade e de adensamento do material. Por fim é proposto um novo método para obtenção coeficiente de adensamento vertical (Cv) e feita uma análise comparativa com métodos existentes na literatura. / [en] In the present work it is carried out an experimental study of the compressibility characteristics and consolidation of a soft clay. Standard Incremental Consolidation (SIC) and Constant Rate of strain (CRS) - in different speeds - triaxiais tests and consolidation with one drenate tests had been carried trough. The samples had been remoulds in laboratory, from a mixture of bentonita and kaolin, in the ratio 98 : 2 In weight, and confined under isotropic conditions, in order to guarantee one better quality how much to the homogeneity and isotropy of the material. The results are gotten and analyzed through the typical curves for consolidation tests. The values of the parameters of compressibility and consolidation of the material are gotten. Finally a new method for attainment of the vertical consolidation coefficient (Cv) and made a comparative analysis with existing methods in literature is considered.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15646号 / 工博第3304号 / 新制||工||1499(附属図書館) / 28183 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 勝見 武, 准教授 木元 小百合 / 学位規則第4条第1項該当