Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

published_or_final_version / Applied Geosciences / Master / Master of Science

No description available.

Drystone walls have been used extensively around the world as earth retaining structures wherever suitable stone is found. Commonly about 0.6m thick (irrespective of height), there are about 9000km of drystone retaining walls on the UK road network alone, mostly built in the 19th and early 20th centuries, with an estimated replacement value in excess of £1 billion[1]. Drystone wall design is traditionally empirical, based on local knowledge of what has worked in the past. Methods vary from region to region, driven by both custom and the nature of the materials available. Design is not necessarily optimised, and includes unknown margins of safety. There is a recognised need for guidance on the assessment and maintenance of dry stone retaining walls, as no suchdocumentscurrentlyexist. Thisthesisdocumentstheconstructionofaseriesoffull-scaletestsdesignedto provide sufficient information to validate current theoretical and numerical analysis techniques. The development of a unique test rig is detailed, in addition to the testing regime and results from a programme of five 2.5m high drystone retaining walls. The walls were subjected to localised surcharging and foundation movements, recreating the conditions that many in-situ walls are subject to. Movements such as toppling, bulging and sliding were observed, and recorded using a broad range of instrumentation. This has provided high quality, quantitative data relating to the factors which influence these mechanisms, and their affect on wall stability. Also documented are the associated laboratory tests which have been conducted to determine the mechanical properties of backfill and the walls themselves, as well as the manner in which they interact together. To assist in the analysis of these full-scale tests, a limit equilibrium program has been developed. This package allows the rapid generation of a wall of any size and constructed with any materials. The limit equilibrium program has then been used in conjunction with the data from the full-scale and laboratory tests to analyse observed drystone wall behaviour. These include the phenomena of toppling, bulging, bursting, sliding and individual block rotation. In each case, the underlying causes of such movements have been determined, and the critical parametersidentified.

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 357-378).

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 181-186).

published_or_final_version / Civil Engineering / Master / Master of Philosophy

Thesis (Ph. D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves [268]-284).

Centrifuge modeling technique is widely used in geotechnical research. Due to the complexity of geosynthetic-reinforced soil retaining walls (GRS-RWs), the centrifuge models of such walls are typically constructed in one stage, where the model is prepared to full height under 1-g and then spun in a centrifuge to the desired g-level or till failure. However, for a retaining wall built in the field, the placement of new soil layer and compaction induces deformations on the previously constructed soil layers, and the wall facing is aligned according to the design at each construction stage. The different construction sequences will lead to differences in the wall performance, including the stress mobilized in the geosynthetic layers. In this study, a multi-stage constructed centrifuge modeling technique was proposed to simulate the construction sequence in the field. The wall facing deformation, tensile force in the geosynthetic layers, and lateral earth pressure behind the wall facing were measured and compared with the traditional one-staged centrifuge model. The results were verified with actual field measurements. The results obtained from multi-staged construction compared favorably to the field measurements. In addition to the construction sequence, the backfill close to the wall facing is usually not as well compacted in the field. The effects of such loose front backfill were also studied by a series of centrifuge models of reinforced soil retaining walls. In addition to the centrifuge modeling of the reinforced soil retaining walls, two series of finite element models were conducted to further study the wall performance. The first series of numerical models included a unified sand model, which was implemented into Abaqus to simulate the backfill. The sand model was firstly calibrated based on the triaxial test results; then, it was used to simulate the wall performance under gravity and dynamic loading. An additional series of FE models were constructed in OptumG2, a 2D finite element geotechnical software to numerically study the influence of loose front and construction sequence of the concrete block reinforced soil retaining walls. Based on the results of centrifuge modeling, simulation of the construction sequence is necessary to obtain a satisfactory assessment of GRS-RWs performance. In this study, the models prepared with multi-staged construction techniques showed better agreement with the field measurements than the models prepared with one-staged construction. In addition, the models with reinforcement simulating the stiffness of the prototype geogrid showed better agreement with field measurements than the models with reinforcement simulating the strength of the prototype geogrid. Besides, a loose front probably existed in the concrete block walls during the field construction based on the comparison of the test results and field measurements. Conclusions from the centrifuge modeling studies were verified by FEM analysis. The dynamic simulation results showed that the studied gabion walls are stable when subjected to a horizontal acceleration up to 0.4 at the bottom of the wall.

[pt] Nesta dissertação é apresentada uma nova técnica para estabilização de encostas através da construção de um muro de gravidade usando pneus e solo. Esta técnica foi desenvolvida dentro de um trabalho de pesquisa realizado pela PUC-Rio, em colaboração com a Fundação Geo-Rio e a Universidade de Ottawa (Canadá). O trabalho consistiu na construção e análise de um muro experimental de solo- pneus localizado em Jacarepaguá, Rio de Janeiro. O muro possui 60m de comprimento e 4m de altura, sendo constituído por camadas horizontais de pneus preenchidos com solo residual compactado e amarrados entre si com corda ou arame. Atrás do muro de pneus foi executado um retro-aterro com 6m de altura, constituído do mesmo solo utilizado no muro de solo- pneus. O muro é composto por 4 seções com características diferentes quanto ao tipo de amarração, geometria e configuração dos pneus (cortados ou inteiros). Apresenta- se neste trabalho um estudo do comportamento tensão vs deformação do material solo-pneus das 4 seções do muro. Os valores previstos numericamente foram comparados aos resultados da instrumentação de campo, com o objetivo de obter os parâmetros de deformabilidade do material. Para a representação do comportamento tensão vs deformação do material solo-pneus, utilizou-se o modelo elástico linear. Foi considerada a existência de 7 camadas distintas do material solo-pneus, permitindo a variação do módulo E ao longo da altura do muro. O solo do retro-aterro foi representado pelo modelo elástico não linear (hiperbólico). Dentre as principais conclusões, pode-se ressaltar que o uso de pneus cortados facilita o processo construtivo e reduz a deformabilidade do muro. A amarração dos pneus com corda, apesar de menos eficiente que a amarração com arame, apresenta-se como a melhor alternativa quando se considera a relação custo vs benefício. A utilização de solo-pneus apresenta-se como uma alternativa que combina a eficiência mecânica do pneu e o baixo custo de execução quando comparada às técnicas convencionais de estabilização de encostas. / [en] Construction of a retaining wall using scrap tires and soil is presented in this thesis. The technique was developed as part of a research program at PUC-Rio in collaboration with University of Ottawa and Geo-Rio. The present work consisted of building and analyzing an experimental retaining wall which was constructed in Jacarepaguá, Rio de Janeiro and made of scrap tires and soil. The wall is 60m long and 4 meters high, made of horizontal layers tire, tied with ropes or wires, filled with compacted residual soil. The backfill was 6 meters high using the same residual soil. The wall has four different cross sections which have distinct geometry, tire configurations (cut tires and entire tires) and tire connections.It is also presented a study on the stress strain behavior of the soil tire composite, which shapes the four different cross sections. The numerical results were compared with field measurements in order to obtain the deformation characteristics of backfill. The retaining wall material was considered to exhibit a linear elastic behavior. The construction procedure was numerically simulated in seven increments and allowing variation of modulus of deformation of the wall with the height of the wall. The stress strain behavior of the backfill was simulated with the use of the hiberbolic model.Among the major conclusions it worth mentioning that the use of cut tires facilitates the construction procedure consequently reducing the deformation of the wall. The use of rope to tie the tires, although less efficient than the use of wire, is a better alternative from the cost effectiveness point of view. The use of tires and soil is an attractive alternative to build retaining walls, which associates efficient mechanical performance with low cost, when compared to the conventional methods to stabilize slopes. / [es] En esta disertación se presenta una nueva técnica para estabilización de encostas a través de la construcción de un muro de gravedad usando neumáticos y suelo. Esta técnica fue desarrollada dentro de un trabajo de investigación realizado por la PUC Rio, en colaboración con la Fundación Geo Rio y la Universidad de Ottawa (Canadá). El trabajo consistió en la construcción y análisis de un muro experimental de suelo y neumáticos localizado en Jacarepaguá, Rio de Janeiro. EL muro posee 60m de largo y 4m de altura, y esta compuesto por camadas horizontales de neumáticos llenos de suelo residual compactado y amarrados entre sí con cuerdas o alambre. Detrás del muro de neumáticos se ejecutó un retro aterro con 6m de altura, con el mismo suelo utilizado en el muro de suelo neumático. El muro está compuesto por 4 secciones con características diferentes respecto al tipo de amarre, geometría y configuración de los neumáticos (cortados o enteros). Se presenta en este trabajo un estudio del comportamiento tensión vs deformación del material suelo neumático de las 4 secciones del muro. Los valores previstos numéricamente fueron comparados con los resultados de la instrumentación de campo, con el objetivo de obtener los parámetros de deformabilidad del material. Para la representación del comportamiento tensión vs deformación del material suelo neumáticos, se utilizó el modelo elástico lineal. Fue considerada la existencia de 7 camadas distintas del material suelo neumáticos, permitindo la variación del módulo Y a lo largo de la altura del muro. El suelo del retro aterro fue representado por el modelo elástico no lineal (hiperbólico). Entre las principales conclusiones, cabe resaltar que el uso de neumáticos cortados facilita el proceso constructivo y reduce la deformabilidad del muro. El amarre de los neumáticos con cuerdas, a pesar de menos eficiente que el amarre con alambre, resulta ser la mejor alternativa cuando se considera la relación costo vs beneficio. La utilización de suelo neumático se presenta como una alternativa que combina la eficiencia mecánica del neumático y el bajo costo de ejecución cuando se compara a las técnicas convencionales de estabilización de encostas.