Elasto-Viscoplasticity Dynamic FEM Analysis For Geogrid Reinforced Soil Retaining Wall

Reinforced soil retaining wall (RSRW) is a kind of composite structure composed with panel, reinforcement and fill. It was used widely as retaining structure in many types of civil engineering, such as highway engineering, water transport engineering, water conservancy project, railway engineering and so on, enormous economic benefits, social benefits and environmental benefits were obtained. Nevertheless, the deformation behaviour and working mechanism of reinforced earth structures have not well understood and rational analysis theory and design methods for these structures are not available. The theoretical study cannot fulfill the rapid and wide requirements in engineering design and construction. Moreover, as mixture made of the high molecular polymers, the geosynthetics usually display noticeable rheologic behaviour under long-term application of tensile forces at a given environmental temperature. Such creep characteristics will affect the long-term performance of reinforced earth structures. As consequence, an intensive study is required for rationally evaluating the long-term performance of reinforced earth structures when rheologic behaviour of geosynthetics is taken into consideration.Therefore, in this dissertation, the retaining wall reinforced by geogrids is taken as a representative reinforced earth structures. The geogrid and soil are synthesized as composite materials. The interaction between geogrid and soil is overlooked so as to resolve the wideness problem of string material. It is convenient for numerial calculation. By this way, the creep property of geogrid is inverted as elastoplastic and researched. The interaction between soil and geogrid is not advised in order to do numerial calculation about geogrid wall.In this dissertation, based on research findings at home and abroad on RSRW, using methods of theoretical analysis and numerical simulation, the structural characteristics and failure mechanism of geogrid RSRW were studied. The main work and conclusions in this dissertation are as follows:(1) The important research findings of RS theory were reviewed,such as interaction mechanism between soil and reinforcement, analysis theory of RS. The Mode of fracture on analysis of RSRW were clarified.The main contents and analysis method on stability analysis of RSRW were clarified.(2) The rheology theory, constitutive equation about soil and geogrid and linear elastie-viseoplastie theory are discussed. Besides, the nonlinear rheology property of the viscoelastic, viscoplasticity or elastie-viseoplastie about soil and geogrid is discussed so as to study the nonlinear creep displacement. In the end, the calculation of rheology theory is seriously researched.(3) The elastoplastic constitutive model of soil were discussed. Based on different yield criterion, the elastoplastic constitutive matrix of soil was obtained for numerical analysis. Strain consistency concept was introduced as a model for soil-reinforcement interaction in strength analysis of geogrid RSRW. Then the elastic matrix of soil-reinforcement composite material was achieved by composite theory and self-consistent method. Finally, the deformation and failure process of soil-reinforcement composite material was analyzed, accordingly an yield criterion which can be served for frontal three phases of the process was obtained.(4) Using constitutive model of soil and soil-reinforcement composite material, a elastoplastic dynamic numerical analysis program was compiled by FEM. Using it, the structural characteristics of the step wall with equal-height were analyzed. Through numerical analysis, the distribution and evolvement disciplinarian on displacement, stress, reinforcement pull and plastic zone of RSRW were exhibited roundly, and consistent with the results. It is proved that the present numerical analysis method is correct and reliable.(5) The constitutive relation of geogrid and soil creep is studied and the creep constitutive relation is derived based composed material theory. The increment-iterate method is used for resolving 2-D rheology problem. Comepared to numerical calculation not considered creep property of geogrid, the software of ABAQUS is used to resolve variant regularity of displacement, stress, pulling force and plastic zone of geogrid retaining wall. The calculation declares that the creep property is not overlooked in the project practice.