ANALYTICAL STUDY OF SEISMIC RESPONSE OF RETAINING WALL IN INHOMOGENEOUS SOIL

Results obtained from geotechnical studies show that the amount of shear wave velocity in various parts of soil is dependent on location of each particle. Therefore, changes of shear wave velocity in soil depth introduce soil as an inhomogeneous material. This research studies the seismic performance of retaining wall in inhomogeneous soil through presenting a proper model which considers mechanism of soil-wall system. In this study, analytical studies have been done in plane strain with rigid retaining wall and linear viscoelastic soil. In order to understand seismic performance of retaining wall, lateral pressure of soil on wall, shear force of retaining structure and bending moment on the wall are presented. Results of this research show that the amount of lateral earth pressure on the wall is dependent on changes of soil shear wave velocity, seismic excitation frequency and geometric parameters of system and response of system is different from homogenous soil. Distribution of inhomogeneous soil lateral pressure expresses that by increasing shear wave velocity at soil surface to shear wave velocity at soil base, location of maximum horizontal stress change from 0.55H to 1H (H: height of retaining wall). In addition, by increasing the damping coefficient of the soil, the lateral pressure exerted on the structure decreases. In the case where the damping coefficient is equal to zero, the amount of horizontal stress increases significantly. The vertical stress of soil is maximum in the wall toe while the amount of horizontal stress is minimum at the same point. Critical vertical pressure distribution occurs in a specific excitation frequency and at the same frequency maximum amount of lateral pressure is applied on the wall. Results also show that lateral earth pressure on retaining wall makes it similar to the behavior of cantilever beam. Thus, implementing the inhomogeneous properties of soil presents a more realistic image of retaining structures and improves design of these types of structures.