深部洞室开挖卸荷分区破裂机制的动力分析

随着地下工程开挖深度的增加，深部岩体将处于高应力和复杂的地质环境中，产生与浅埋洞室破坏模式迥异的分区破裂现象。深部洞室在动力卸荷作用下，基于应变梯度理论和损伤软化模型，建立了弹塑性损伤软化动力模型，推导了含有应变梯度项的运动方程、平衡方程和边界条件，提出相应的破坏判据，采用Runge-Kutta方法和Matlab数值软件求得不同卸载时刻围岩附加位移场、应力场和开挖后围岩总位移场、应力场，得到深部洞室围岩分区破裂的动态形成过程和发展规律。由理论计算值与地质力学模型试验实测值对比分析得知，围岩的径向位移、径向应力和切向应力出现波峰和波谷交替振荡的变化规律，理论计算得到的破裂区和非破裂区的宽度和数量与试验实测值有很好的一致性，证实了该模型分析分区破裂现象的适用性，对以后深部地下工程围岩变形破坏和支护设计提供理论支持。

Zonal disintegration mechanism analysis based on strain gradient of deep surrounding rock mass under dynamic unloading effect

With the increase of excavation depth, the deep rock mass is in high stress and complicated geological environment and the zonal disintegration phenomenon is observed at some projects, which is largely different from failure modes of shallow caverns. Under the action of dynamic unloading, an elastoplastic damage softening dynamic model is put forward based on the strain gradient theory and damage softening model. The dynamical equation, the equilibrium equations, boundary conditions and the failure criterion are deduced by considering the strain gradient. The theoretical solutions of radial displacement, radial stresses and tangential stresses of deep surrounding rock mass at different unloading times are calculated by Runge-Kutta and Matlab. The total displacement and stress fields of surrounding rock are also obtained after excavation. The dynamic formation and development regularity of zonal disintegration in deep caverns are achieved. The radial displacement, radial stresses and tangential stresses of deep surrounding rock mass are exhibited as an oscillating mode. The number and the width of zonal disintegration are in good agreement with the data of model tests. The applicability of the elastoplastic damage softening dynamic model for zonal disintegration in the explanation of zonal disintegration is confirmed. This model can also be used to provide theoretical support for the deformation and failure of surrounding rock in deep underground engineering.