深埋隧道开挖过程动态及破裂形态分析

 地下工程开挖过程中，在洞室围岩中会产生拉压交替变化区，当地应力过大时，会产生分区破裂化现象。为了解释洞室围岩拉压交替变化和分区破裂化现象，根据隧道开挖卸荷这一动力学特征，建立隧道开挖过程的动态分析力学模型和计算模式，由此导出由开挖卸荷引起的扰动应力、扰动应变和扰动位移满足的平衡方程、物理方程、几何方程和边界条件。根据实际的位移约束条件，假设位移试函数，利用Hamilton时域变分原理，考虑时域变分条件和约束变分条件导出围岩体的积分–变分方程组，建立该方程组的模态矩阵。在给定开挖卸荷路径和零初始条件下采用Duhamel积分，得到离散振动方程组的稳态响应。通过矩阵变换，得到隧道围岩体扰动应力、应变和位移的解答函数式。算例分析表明，所给出的理论和方法能正确地反应出隧道开挖引起围岩内的动态过程，并能有效地对开挖引起的围岩的破坏形态进行评价。

ANALYSIS OF DYNAMIC AND FRACTURED PHENOMENA FOR EXCAVATION PROCESS OF DEEP TUNNEL

Tension-compression alternating regions can be formed around the rock mass during excavation process. The zonal disintegration phenomena may be brought when the geostress is too large. In order to interpret the tension-compression alternating and zonal disintegration phenomena，the dynamic mechanical model and calculation model of tunnel excavation are presented based on dynamic characteristics of tunnel excavation unloading. And the equilibrium physical equation，geometric equation and boundary condition equation are derived，which are satisfied by the disturbance stress，disturbance strain and disturbance displacement caused by the excavation unloading. Trial function of displacement is assumed considering the practical displacement constraints condition，and integral-variational equation group of the surrounding rock；and its modal matrix is induced by Hamilton time-domain variation principle considering time-domain variation and constraint conditions. The steady-state response of discrete vibration equation group is obtained using Duhamel integral in setting excavation unloading path and zero initial condition. By matrix transformation，the solutions of surrounding rocks disturbance stress，strain and displacement are obtained. The analyses of examples show that the theory and method can correctly reflect the dynamic process caused by excavation；and they effectively simulate the zonal disintegration phenomena of the rock mass.