境界要素特性曲線結合法による岩盤斜面の弾塑性解析

抄録

The coupled boundary element-characteristics method is successfully applied to thecut slope problem. The elasto-plastic behaviour of drained homogeneous rock slopes of slope angle greaterthan 50 degrees has been analyzed to investigate the failure mechanism and premonitory phenomena. Rock massis assumed, in the present analysis, to be a dilatant Mohr-Coulomb material with weight, and the associated flow rule is used to compute the displacement within the plastic zone. Firstly, analyzing the boundary between the elastic zone and the passive plastic zone, it is clearly shown that the initial lateral stress, as well as the gravity, plays an important role in determining the depth of plastic zone downward from the toe of slope, and the high lateral stress results the tension failure in upper slope surface and the growth of plastic zone downward from the toe of slope. Secondly, from the analysis of displacement and plastic strain within the plastic zone, it is clarified that a small depth of plastic-zone downward from the toe of slope is always associated with the concentration of plastic shear strain on a slip line through the toe of slope. The angle between the slip line and the slope surface generally coincides with the fracture angle of rock, and this analytical result is compatible with the sliding of a wedge-shaped territory observed by the centrifuge experiment. Moreover, it is analytically clarified that the expansion of plastic slope surface is mainly associated with the dilatancy on the slip line, which finally grows into the slide plane, and such a dilatant behaviour is available for the prediction of subsequent progressive failure.