2014 Volume 70 Issue 2 Pages I_397-I_408
Case study regarding a shallow slope failure by heavy rainfalls is described in this paper. The site where the slope failure took place is located in Chita Peninsula, Aichi Prefecture in Japan. The catastrophic failure occurred on a slope consisting of strongly weathered Conglomerate and Siltstone with the inclined angle of 40 to 45 degrees. The collapse was definitely triggered by heavy rainfall brought by Typhoon No.18 in 2009. In an attempt to manifest a possible scenario of the slope failure, the geological profile of the slope was in detail examined by in-situ tests, together with the engineering properties of the surface soil by various laboratory tests using undisturbed soil sample. Two-dimensional saturated-unsaturated seepage flow analysis simulating the rainfall record before and at the collapse was also carried out. Similar analysis was performed for a heavy rainfall recorded in the preceding year of 2000, for which no collapse was observed. It was manifested that the slope collapsed involving with some loss of apparent cohesion of the surface soil due to saturation of the surface soil. In a comparison with similar heavy rainfall in 2000, it was suggested that the amount of preceding rainfall before the collapse seems vitally important to govern the occurrence of the slope failure.
