Study on Dip Slope Failure at Higashi Takezawa Induced by 2004 Niigata-Ken Chuetsu Earthquake

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 eŠects of the irregular geometry of the sliding plane and its strainsoftening properties, a reasonable simulation of the process of this slope failure could be provided.

Constitutive and multi-block modeling of landslides on saturated sands along slip surfaces

“…The effect (b) above is the usual state in slides in the field, and is caused by the law of physical equilibrium where masses move toward a more stable configuration. It has been modeled in a cost-effective manner by an iterative procedure using the Jambu stability method by Deng et al (2011), as well as by the multi-block model by Stamatopoulos et al (2011). The multi-block model, described below, has the advantage of ensuring displacement compatibility during motion and will be applied in the present work.…”

“…Earthquake shaking has caused significant deformations, and even large scale failures, in slopes consisting of saturated sands (Sassa et al, 1996;Deng et al, 2011). The sliding-block model (Newmark, 1965) is frequently used to simulate movement of landslides triggered by earthquakes (Gerolymos and Gazetas, 2007) and other causes (Davies et al, 1993).…”

Simplified Multi-Block Constitutive Model Predicting the Seismic Displacement of Saturated Sands along Slip Surfaces with Strain Softening

“…In addition, table 1 and Fig. 3 gives two tests performed in a simple shear device that represent adequately the undrained response of the saturated sand along the slip surface of the Higashi Takezawa Earthquake Engineering -From Engineering Seismology to Optimal Seismic Design of Engineering Structures landslide [1]. It can be observed that in all tests the shear stress first increases at a decreasing rate with shear displacement and reaches its peak value in a few millimeters or centimeters.…”

“…Slopes consisting of saturated sands have recently moved down-slope tens or hundreds of meters under the action of earthquakes [1][2][3]. This large slide movement is usually associated with the generation of large excess pore pressures, as a result of grain crushing [3].…”

“…This response depends on the drainage conditions and may alter as a result of dissipation of excess pore pressure in saturated sand. Yet, under earthquakeinduced slides, triggering and slide movement are so rapid that dissipation of excess pore pressure does not occur and saturated sands behave in an undrained manner [1][2][3], [16]. It is inferred that for predicting the triggering and the slide movement of such slides, only the shear resistance versus shear displacement soil response under undrained conditions may be predicted.…”