COMPARISON OF SEISMIC DISPLACEMENT OF GRAVITY RETAINING WALL AND REINFORCED SOIL WALL ACCORDING TO PERFORMANCE BASE

The performance design procedure of retaining wall is based on the permanent deformation of walls after the earthquake. During earthquake, wall acts as a solid element with coupled rotation and sliding movements on non-elastic base. This mechanism develops yield surface in wall and backfill. The expected performance of the gravitational wall in earthquake is dependent on amount of load and lateral displacement. In this study, two types of walls considered for follow up, non-reinforced gravitational wall (NRGW) and reinforced gravitational (RGW) wall reinforced with geosynthetic. The NRGW modelled in FLAC software with finite difference method. Nonlinear time history analysis with six different earthquake record (Azmit 1997-1998, Tabas 1997 and Montenegro 1997), applied in the model. The geotechnical characteristics of the wall with two types of soil are declared in Table 1. The geometrical dimension and analytical model is depicted in Figure 1.The performance of RGW reinforced by geosynthetic, predicted by dynamic methods through limitations on lateral forces. The slope of wall façade (b), angle of shearing resistance of the backll (f'), apparent soil-reinforcement frictionfactor (fs/GSY), ratio of reinforcement length to wall height (L/H), ratio of reinforcement spacing to wall height (s/H),critical seismic coefficient (kc), were the assumed parameters in the parametric study of the wall performance, as depicted in Figure 2. Table 2 declares the amount of assigned values for assumed parameters in the parametric study.The analysis of the NRGW indicated that two mechanism of failure would be occur; a) failure due to the great displacement of soil beneath the foundation around the toe, will lead to huge distortion of the wall, b) failure is attributed to the residual displacement of the wall greater than 10 percent of wall height. The analysis of the RGW indicated that the failure is initiated on the sliding surface and all the geosynthetic reached to the ultimate capacity. Total collapse would occur in the backfill and propagate in the wall. Through this approach, the maximum acceleration and its equivalent displacement as the critical parameters for the failure of the RGW stated.

Keywords:

Permanent deformation , Earthquake , Performance level