DESIGN OF RETAINING WALLS

Design of Retaining Walls

Abstract

A simplified method for the dynamic analysis of reinforced retaining walls during earthquakes is presented, based on the plane strain assumption and the concept of the equivalent material behind the wall. The dynamic soil-retaining wall interaction is included in this method and the system is divided into several subregions. The greatest merit of this simplified method lies in that it includes all the important factors which may affect the response of the reinforced retaining wall. Since this simplified method is based on the finite and infinite elements coupled method, not only can the natural soil and the reinforced retaining wall be simulated rigorously but also the wave propagation mechanism in the system can be modelled more realistically. Some numerical results from the analysis of a reinforced retaining wall under SV- and P-wave incidences demonstrate that the backfill soil behind the retaining wall has considerable effects on the dynamic response of the wall during higher frequency wave incidences and thus the change of material properties of the backfill should be considered in the seismic design of retaining projects.

Table of Contents

Abstract2

Introduction4

Statement and Solution Method of the Problem6

Effect of Backfill Soil on the Retaining Wall Response9

Analytical Studies12

Behavior of soil retaining walls on deformable foundations12

Dynamic active earth pressure on cantilever retaining walls14

Seismic stability of retaining walls with surcharge17

Active earth pressure in retaining walls with reinforced cohesive-frictional backfill19

Two-parameter beam-column model and back analysis for flexible earth retaining walls21

Conclusion23

References25

Appendix27

Design of Retaining Walls

Introduction

The evaluation of the dynamic response of a retaining wall is a very important topic in the design of the retaining project. Generally, a retaining wall is a finite structure and its surrounding soil is an infinite medium. Therefore, in the numerical simulation of the retaining wall-soil system, the finite element method is suitable to model the retaining wall as well as its near field of the soil and the infinite elements or some other special techniques are useful to consider the infinite extension of the far field of the soil. Since the surrounding soil of the retaining wall is divided into the near field and the far field, the no homogeneity of the soil in the near field can be easily modeled by finite elements (Zienkiewicz, 1975, pp.52).

On the other hand, an earthquake wave usually contains various wave types such as Rayleigh, SH-, SV- and P-waves. These waves originate from the epicenter and propagate from the far field to the retaining wall. Although some analytical work on this aspect has been done in other areas, the numerical simulation of the infinite extension of the soil and the wave propagation in the soil-retaining wall system was not considered in the previous studies of the dynamic response of the soil-retaining wall system. Without doubt the mechanism of input earthquake waves should be modeled more appropriately in a soil-retaining wall system so that realistic numerical results can be obtained.

The concept of the infinite element was presented by Bettess and Ungless in the ...