大深度立坑の時間依存性挙動および破壊挙動の有限要素解析

Abstract

Shaft plays an important role in accessing or ventilating to deep underground, so it is necessary to assess its long-term stability. But little knowledge about the long-term behavior of shaft has been obtained from in-situ measurement, theoretical study and numerical simulation. In this study, time-dependent behavior and failure process of deep shaft was simulated with the aid of non-linear rheological constitutive equation of rock. This simulation focused on the effect of gravity and the deformation behavior parallel to the direction of excavation, which has hardly been examined with horizontal roadway or tunnel.Simulation with the model of 1000m deep shaft was carried out, and the effect of rock properties and rock stress conditions was examined. It was found that time-dependency, ductility, Poisson's ratio of rock mass and the ratio between horizontal and vertical rock stresses had an effect on failure process around the bottom of shaft. In addition, simulation with vertically and horizontally loaded disc-shaped model was carried out to investigate the effect of vertical rock stress and gravity in detail. It was found that the vertical deformation of shaft wall was much smaller than the radial one just before failure, but that the vertical rock stress and gravity had a large effect on failure process and long-term stability of shaft.