A STUDY ON DETECTION OF POTENTIAL RISK OF SLOPE FAILURE BY MONITORING OF SHEAR STRAIN IN SHALLOW SUB-SURFACE OF A SLOPE AT EXCAVATIONS

Abstract

 This study discusses on availability of simplified monitoring of slopes for prevention of workers being buried in soil at excavations. A compact strain meter was developed to measure increment of shear strain θ in shallow sub-surface of slopes. A full scale model test was carried out in a model slope composed of soft deposit of Kanto-loam and 45 degrees of inclination and 3.5m of height. The model slope did not fail immediately after a completion of the final excavation, and 24minutes of time lag existed prior to failure. The relationship between θ and the displacement shows good agreement in the increase. Similar reactions to the creep strain curve were observed in θ. A couple of minute time could be provided for escape by identifying either 2nd or 3nd creep. In addition, numerical analyses were performed to investigate the distribution of θ in slopes. A clear increase of θ was confirmed especially at the inside of failure block when the slopes were getting to fail. It was clarified that the potential risk of slope failure is detectable by the monitoring. It is also considered that warning by the monitoring can save workers' lives by escape.