A SIMPLE METHOD FOR EVALUATING SEISMIC FAILURE POTENTIAL OF RETAINING WALLS ON SLOPES

Abstract

In the design practice of retaining walls which support road embankments, stability under the action of strong earthquake ground motion is usually not examined. However, collapse of road embankments in mountainous area often results in cutting off road traffic and complete isolation of people in the neighborhood for a long time. The author surveyed a number of damaged and undamaged road embankments in the mountainous area where strong ground motions were recorded during the 2004 Niigataken-Chuetsu Earthquake. It was revealed that catas trophic failure of embankments constructed on sloping foundation soils were in many cases triggered by damage of retaining walls and most of such damaged retaining walls failed in the mechanism of the bearing capacity failure of the foundation soil. In this study a simple method to examine the seismic stability of existing retaining walls is developed, which evaluates a factor of safety for the bearing capacity failure of foundation on slope under combined loading in conjunction with soil strength parameters obtained by dynamic cone penetration tests using a portable testing device. A good correlation was found between the factor of safety of the surveyed walls derived from the method and the observed deformation of the walls, confirming the effectiveness of the method to identify seismically unstable walls out of existing walls.