Seismic response analysis of tailing dam foundation on discontinuous rock masses and counter measure design

Sasaki, Takeshi*; Koshigai, Masaru*; Horikawa, Shigeo*; Fukushima, Shigeru ; Ohara, Yoshiyuki

The authors report an earthquake response analysis of a tailing dam with the foundation of the jointed rock masses. The non-linear deformation characteristics of the rock joints are assumed the combination of different angle of joint sets as Multiple Yield Model introduced by Sasaki et al. (1994). The geology of dam foundation of granite is classified as CH, CM, CL and D with two joint sets. The vertical and the horizontal angle of joints are combined in the granite. The height of the tailing dam is 10 meters and the width is 30 meters. The water gathering basin is constructed in front of the dam to collects the leakage water throw the rock joints of dam foundation with gravity type retaining wall. The input earthquake motion is assumed the several faults existing around the dame site were moved and the wave motions is calculating the statistic green function theory (Irikura et al.,1991). The non-linear deformation of joint of the normal and the shear direction are both depends on of the confining pressure presented by Bandis et al. (1981) and Kulhawy (1975), respectively. The two section models of the flowing down direction are analyzed by finite element method as the present state and the measures state. Collapse of the water gathering basin is fear misgivings by the earthquake motions. Therefore, in order to control of the collapse of water gathering basin with gravity type retaining wall, the additional new small gravity dam will be planed in front of the gravity wall. And section of the orthogonal axes of the dam is analyzed. According to the results, the tailing dam is sound, and the water gathering basin with gravity type wall is collapsed. And the additional small gravity dam considering counter measures is sound and the acceleration at the gravity type wall is one/ third reduction compare with non-counter measures. Therefore, the effect of the additional small gravity dam is very well for the strong earthquake in this analysis.