Abstract
At 8:43 a.m. on June 14, 2008, the Iwate-Miyagi Nairiku Earthquake, which centered on the southern inland of Iwate Prefecture, occurred. In the wake of this earthquake, a landslide caused by the specificity of the geological structure and the vulnerability of the ground occurred in the Ichinonobara region in Ichinoseki, Iwate. In order to determine the slip surface of the landslide, the behavior was observed by using a borehole with a pipe strain gauge. However, no obvious landslide movement was observed. Therefore, various indoor tests were conducted using boring core samples, and data that shows evidence of the slip surface was obtained from colluvial soil at a depth of 47 to 48 m as the result of a quantitative analysis of smectite and an improved swelling pressure test based on an oven drying method. It became apparent that these physical and chemical test methods are effective for determining the slip surface of a landslide where no landslide movement is observed.
