Seismic Response And Dynamic Stability Analysis Of Reinforced Retaining Wall

Reinforced retaining wall was developed with the increasing popularity due to its good performance, low price and aesthetic appearance.It had been proved by practices and experiments that reinforced retaining walls exhibited good seismic performance, however, it is still necessary to conduct seismic design of the structure when the earthquake excitation is strong.This paper investigates several key issues concerning seismic response and dynamic stability. Accordingly the contents of this dissertation include five parts as below:(1) In this study, reinforced soil is regarded as macroscopically well-distributed composite materials; reinforcement strip as reinforcing materials. Based on the shear beam model, the motion equation of backfill soil is established to get the horizontal shear strain of backfill soil under horizontal earthquake loads. In addition, reinforcement strip is simplified as one-dimensional no quantity elastic rod and it is assumed that there is no relative displacement between backfill soil and reinforcement. In view of these assumptions, axial strain of reinforcement strip equals the horizontal shear strain of backfill soil; tension equation of reinforcement strip under horizontal earthquake loads is established to analyze dynamic tension of reinforcement strip under the harmonic earthquake loads, thereby testing the internal stability of reinforced retaining wall. Finally, the method is applied to a case of reinforced retaining wall, and FEM (ADINA) is used to verify the computational model. The result shows that the computational model accurately reflects the actual stress the reinforcement strip bears and achieves the cooperation of the reinforcement strip, soil body and the panel.(2) Taking the role of reinforcement strip into account, and taking the slip surface as logarithmic spirals according to the upper bound limit theory, the study establishes an overall stability analysis model of reinforced retaining walls. A dynamical search model is set up for the slip surface to carry out the dynamic analysis in which the overall stability of the retaining wall changes with the design parameters. The application of the model to a project indicates that the location of critical slip surface varied with the design parameters of reinforced retaining wall. The overall stability analysis of the reinforced retaining wall based on the dynamic search model of slip surface precludes the irrationality of the stability analysis caused by the specification of the most dangerous slip surface through experiences, or by not taking into account the role of the reinforcement strip. Applying genetic algorithms to the dynamic search of the sliding center of the most dangerous slip surface avoids the search's running into a local minimum in optimal design. At last, the concept and the computational formula of reinforced retaining wall's sensitivity based on coefficient of the overall stability is made to get the computational formulas of the sensitivity of the parameters in coefficient of the overall stability. Then the sensitivity degree of each design parameter is obtained grounded on the analysis of the sensitivity of the overall stability factors.(3) On account of the overall stability analysis model, the hypothesis that the displacement of the retaining wall under earthquake loads is equal to the displacement during earthquakes and the displacement after earthquakes is proposed. The sliding block method– Newmark is adopted to calculate the displacement during earthquakes. According to the distortion characteristics of reinforcement strip, the stair distortion is applied to calculate the strip's slipping frictional resistance in its slipping along with the soil after earthquakes and the function principle is adopted to establish the computational model of the displacement after earthquakes; the designing procedures of the retaining wall controlled by the displacement is also given. At last, the model is applied to a project to be verified.(4) According to the actual damage of reinforced retaining wall, performance function is established for internal and external stability. Reliability of internal and external stability was calculated using respectively JC method and Monte Carlo Method by the MATLAB. Through the comparison of the results of the calculations, it is found that JC method is much more precise than Monte Carlo Method, thus being suitable for the widespread use in the analysis of the dynamic reliability of reinforced retaining wall.(5) Nonlinear FEM (ADINA) is used for the mechanical analysis of reinforced retaining walls. In this analysis, 3-D nonlinear FEM model is built in consideration of the cooperation and interaction among backfill soil, panel and reinforcement strip; The backfill soil is simulated by nonlinear static and dynamic elastic-plastic model; the reinforcement is simulated by the dual-phase enhanced linear elastic-plastic model which can describe the intensified features of the reinforcement; the interaction of soil and retaining structures is simulated by the friction-element.The application to a project yields the distribution law of the strip's most dollar point of force and the changing rules of the strip's pulling force around earthquake. Then the calculation, comparison and analysis of the seismic response of the retaining wall with EL-Centro waves and under different supporting and protecting operations are made to obtain the influences of different parameters towards the seismic response of the reinforced retaining wall.