Collapse mode of rock mass induced by a concealed karst cave above a deep cavity

Abstract

Reliable prediction of the potential collapse region of rock mass is a key challenge for deep underground cavity excavation, especially if a concealed karst cave is located above the excavated cavity. Because of the effect of the blast vibration, a possible collapse would occur at a certain region between the concealed karst cave and the excavated cavity. This paper aims to study the roof collapse of a deep buried cavity induced by a concealed karst cave base on a two-dimensional failure mechanism by using upper bound theorem. The failure mechanism is constituted by arbitrary curves which is similar to the collapse observed in an actual cavity excavation. The shape and range of the collapse block is determined by virtual work equation in conjunction with variational approach. The results obtained by the presented approach are approximate with the numerical results provided by finite difference code, which indicates that the proposed method in this work is valid.

摘要

可靠地预测由于地下工程施工导致的围岩塌落范围是地下工程施工中遇到的一个关键问题。尤 其当地下硐室上方存在隐伏溶洞时, 由于施工过程中爆破振动的影响, 增大了地下硐室与隐伏溶洞之 间围岩发生垮塌的可能性。针对这一现象, 利用任意线型的曲线构建了由于隐伏溶洞诱发深埋硐室顶 部围岩塌落破坏的二维破坏机制。在此基础上, 基于极限分析上限定理的虚功率方程和变分法计算得 到了深埋硐室顶部围岩塌落面的解析方程, 并绘制了不同参数作用下深埋硐室顶部围岩塌落面的形状 和范围。为了验证理论结果的正确性, 将计算得到的围岩塌落面理论解和数值模拟得到的数值解进行 了对比。分析表明: 理论解和数值解基本一致, 证明本文的理论计算结果是有效的。