Abstract
An extensive number of slopes failed in the 2004 Niigata-ken Chuetsu Earthquake. Among them, a dip slope containing a weak layer in Yamakoshi Village (currently Nagaoka City) was investigated intensively. Regarding its morphological characteristics, it is argued that the earthquake reactivated a pre-existing failure plane which then formed most of the present sliding plane. In order to reveal the strength properties of the weak layer that formed the sliding plane, including the behavior against cyclic loading, a series of triaxial compression tests and simple shear tests was performed on undisturbed specimens that were retrieved by block sampling from the site. Based on the test results, a stability analysis and the calculation of the earthquake-induced displacement were performed. By extending Newmark's sliding block analysis, while considering the effects of the irregular geometry of the sliding plane and its strain-softening properties, a reasonable simulation of the process of this slope failure could be provided.
