Dynamic response and failure of rock in initial gradient stress field under stress wave loading

Abstract

Once an opening is created in deep underground, the stresses surrounding the opening will be redistributed, inducing a gradient stress field. To understand how the ground rock in such a gradient stress field responses to dynamic stress loading, the gradient stress distribution at a circular opening was first analyzed and the propagation of 1D stress wave in rock mass under gradient stress field was theoretically derived. By using an implicit to explicit solution method in LS-DNA code, the dynamic mechanical behaviors of rock in gradient stress field were numerically investigated. The results indicate that the damage is mainly produced at or near the free face, partly due to the straight action of compressive stress wave and the tensile stress wave generated at the free face. The range of the induced damage zone is narrowed under the conditions of higher gradient stress rate and lower dynamic stress amplitude. However, under lower gradient stress field and higher dynamic stress, the damage becomes severer and wider with discontinuous failure regions.

摘要

深部岩体开挖后, 受应力重分布的影响, 临空面附近的岩体处于梯度应力状态。为研究含梯度 应力场岩体的动态力学响应特征, 首先对圆形硐室的梯度应力分布规律进行分析, 从理论上推导出梯 度应力场岩体在一维应力波作用下的波动方程。通过LS-DYNA 程序的隐式-显式连续计算方法, 对梯 度应力场岩体的动力响应行为进行模拟研究。结果表明, 在岩体受压缩应力波和反射拉伸波共同作用 下, 岩体的损伤主要发生在自由面附近。数值模拟结果表明, 更高的应力梯度率以及更小的应力波幅 值导致损伤区范围更小。然而, 在较小的梯度应力场以及较强的应力波加载下, 岩体损伤更严重, 范 围更广, 并且会产生非连续破坏的现象。