Slope Failures Triggered by Heavy Rainfall

Abstract

Landslides occur frequently during or following periods of heavy rainfall. This is illustrated by the large-scale landslides and debris flows in Quezon Province which were triggered by a series of typhoons and tropical storms last November-December 2004. In order to understand the mechanism and conditions leading to these slope failures, a comprehensive testing program consisting of constant shear stress drained triaxial tests and model slope experiments was performed using sandy materials obtained from a former landslide site in Japan. Results of both element tests and model experiments clearly showed that slope failure is induced due to the development of pore-water pressure in slope. As soil moisture contents within the slope approach critical values, ground deformations are mobilized. Therefore, by properly selecting regions where soil moisture contents must be monitored, possibly in areas where seepage forces will develop, failure initiation in slopes can be predicted. Based on this,a simple monitoring scheme to predict in real-time the occurrence of failures in critical slopes was proposed.