We present a numerical study of spatio-temporal damage evolution and fracture displacements around underground excavation in fractured rock masses. We conduct a comparative analysis of this problem based on a mechanical (M) model by assuming an invariant pore pressure and a hydro-mechanical (HM) model by solving the coupling between the fluid and solid fields. In both models, an elasto-brittle constitutive law is employed to mimic the deformational and failure behavior of intact rocks, while a non-linear stress-displacement relationship is used to account for the normal compression and shear dislocation of natural fractures. In the HM model, we simulate excavation-induced transient groundwater flow in fractured porous rocks based on Darcy's law. The hydraulic and mechanical fields are linked based on the coupling mechanisms of poroelasticity (direct HM coupling) and stress-dependent material properties (indirect HM coupling). Many important HM phenomena such as stress perturbation, pore pressure fluctuation, damage evolution and fracture deformation are realistically captured in our simulation. We find that both direct and indirect couplings play important roles, and the excavation-induced disturbance in rock varies with the coupling degree characterized by the Biot coefficient. One interesting observation is that excavation-induced stress redistribution around the tunnel instantly causes perturbed pore pressure in low-permeability matrix, which gradually becomes dissipated during the post-excavation drainage. We also highlight the role of natural fractures in the tunnel inflow process and elucidate the consequences of spatial and temporal pressure variations. In addition, we analyze the microseismicity occurrence during and after the excavation to gain insights into excavation and drainage-induced responses in the fractured rock. The results of our simulation and analysis have important implications for underground excavation involved in many geoengineering applications such as civil infrastructure, nuclear waste repository and oil/gas/geothermal wellbore systems.

我们对裂隙岩体中地下开挖周围的时空损伤演化和裂隙位移进行了数值研究。我们基于机械（M）模型，通过假设不变的孔隙压力和流体力学（HM）模型，通过解决流体与固体场之间的耦合问题，对该问题进行了比较分析。在这两个模型中，均采用弹塑性脆性本构定律来模拟完整岩石的变形和破坏行为，而非线性应力-位移关系则用于解释自然裂缝的法向压缩和剪切位移。在HM模型中，我们根据达西定律模拟开裂引起的裂隙多孔岩石中的瞬态地下水流。液压和机械领域是基于多孔弹性（直接HM耦合）和应力相关的材料属性（间接HM耦合）的耦合机制进行链接的。在我们的仿真中，现实中捕获了许多重要的HM现象，例如应力扰动，孔隙压力波动，损伤演化和断裂变形。我们发现直接和间接耦合都起着重要的作用，并且在岩石中的开挖引起的扰动随以毕奥特系数为特征的耦合程度而变化。一个有趣的观察是，开挖引起的隧道周围应力的重新分布会立即引起低渗透矩阵中的孔隙压力扰动，在开挖后的排水过程中，孔隙压力逐渐消失。我们还强调了天然裂缝在隧道入流过程中的作用，并阐明了时空压力变化的后果。此外，我们分析了开挖过程中和开挖之后的微震现象，以深入了解开裂和排水引起的裂隙岩体的响应。我们的模拟和分析结果对许多土木工程应用（例如民用基础设施，核废料仓库和石油/天然气/地热井眼系统）中涉及的地下挖掘具有重要意义。