MECHANICAL SIGNIFICANCE OF PROBABILITY OF FAILURE AS AN INDEX FOR PREDICTION OF SLOPE FAILURE

Abstract

The disaster due to the slope failure at the heavy rainfall is one of the most important social problems in the mountainous countries like Japan. The object of this study is the relatively shallow slope failure in the surface soil layer of the slope, since this kind of slide occurs very frequently at the rainfall. There are two approaches to prevent or decrease the disaster : One is to perform the mechanical defensive works such as a retaining wall and the other is to find out the good prediction method of slope failure in order to minimize the damage. It is well known that the measurement of deformation and pore pressure of a slope is very effective for the prediction of slope failure, but it is practically impossible from the economical and technical aspects to measure these factors for a very big number of steep slopes during the heavy rainfall. From this viewpoint, the authors developed the new prediction method of slope failure by using the probability of failure in which only the rainfall intensity is needed as the information during a rainfall.The present paper firstly shows the validity of this method based on many analytical results for the actual failure and the non-failure slopes and after that the mechanical significance of the probability of failure which is just only a conceptional index is verified by the laboratory and the field experiments.