Abstract

Reinforced soil retaining walls are important public structures. Typically there are two kinds of reinforced soil retaining walls: cantilever retaining walls and Geosynthetic reinforced soil retaining walls. While seismic performance of retaining walls is very important for public safety in the event of an earthquake, there are very limited studies on that. The main objectives of the present thesis are to (i) examine the behavior of the interface between structure and soil under various loading and boundary conditions for RC cantilever retaining walls; (ii) conduct sensitivity study on the seismic response of such walls considering the key parameters such as the cohesion (C), friction angle (φ), shear stiffness (Ks), normal stiffness (Kn) and dilation (ψ); and (iii) study the size (height) effect of the relating walls on the seismic performance of such walls.
In order to achieve the above objectives, a baseline model of an RC cantilever retaining wall has been constructed for static and dynamic analysis using the Finite Difference Method (FDM). The data for the baseline model are obtained from a published work on seismic response such a wall subjected to an earthquake in India (1991 Uttarkashi earthquake, 20th October), which used the Finite Element Method (FEM) for analysis. The validated baseline model is then used for an extensive parametric study on the static and dynamic behavior of the system which is not available in the literature.
Based on the results of numerical modeling, in the static condition, wall deformation was decreased by increasing the cohesion (C), friction angle (φ), shear stiffness (Ks), normal stiffness (Kn) and dilation (ψ) values. The dynamic behavior of the wall was quite different from the static behavior. With increasing the values of shear strength parameters (Cohesion and friction angle) and also shear stiffness (Ks), the wall displacements increased whereas with increasing normal stiffness (Kn) value, the wall deformation decreased.
A sensitivity analysis of wall-soil interface parameters on seismic response of the retaining wall was carried out using the ground motion records from Canada earthquake motion database (6th March, Quebec, 2005) and the results were compared to the Uttarkashi earthquake in India. The results of this comparison showed that the response parameters in terms of the retaining wall deformation are similar for both earthquakes.
Moreover, parametric studies on the behavior of the soil retaining walls under Montreal earthquake with three different heights (3 m, 6 m and 9 m), and two different types of soil (clay and sand) and eight input earthquakes motions were performed. Results show that the behavior of wall facing in terms of displacement in both horizontal and vertical direction is different, and the type of soil has a main role in the wall deformation.
Finally, a statistical estimation of parameters between soil and retaining wall structure was done. According to this statistical study, cumulative percentage distribution of cohesion (C) and stiffness parameters (shear and normal) against wall deformation were calculated. Then, lower and upper boundary ranges of wall-soil parameters were established for both static and dynamic condition.