跨断层隧道围岩渐进性破坏模型试验及数值模拟

 断层及其破碎带是隧道开挖过程中常见的不良地质现象，也是围岩不稳定且容易出现事故的地段。以山区隧道施工中常见的IV级围岩为参照对象，利用地质力学模型试验和数值模拟研究跨断层隧道施工过程中围岩的渐进性破坏过程及其受力变形特性。研究结果表明：(1) 位于拱顶之上的断层下盘岩体在隧道开挖后呈悬挑状态，且在靠近断层部位易出现拉裂缝；(2) 隧道开挖使得上覆荷载向隧洞左、右两侧转移，从而导致拱腰以下的岩体往往率先剪切破坏，尤以断层下盘一侧岩体为甚；(3) 隧道开挖将引起围岩应力重分布，若调整后的围岩应力超出岩体自身强度极限时，洞周岩体就会塌落成拱，且位于塌落范围内的岩体切向应力呈“跌落式”下降，此特征可用于判断岩体塌落范围；(4) 隧道开挖后，由于断层的阻隔作用，岩体应力在跨越断层上、下盘时呈不连续、非线性分布的特征。

Experimental study and numerical simulation on progressive failure characteristics of the fault-crossing tunnel surrounding rock

Faults and fractured zones are common unfavorable geological phenomena encountered in the process of tunnel excavation. It is also the place where the surrounding rock is unstable and prone to accidents. In this paper，the weak rock mass of grade IV commonly found in mountain tunnels was selected as the reference object，and geomechanical model test and numerical simulation were carried out to study the progressive failure process as well as the stress and deformation characteristics of the surrounding rock of fault-crossing tunnel. After tunnel excavation，the rock mass of fault footwall located above tunnel arch was in the cantilevered state，and tensile cracks were found near the fault region. Tunnel excavation made the overburden load be transferred to the two sides of tunnel，which often led to the shear failure of rock mass below tunnel waist，especially for the rock mass close to fault footwall. Tunnel excavation caused stress redistribution around surrounding rock. Once the redistributed stress exceeded the ultimate strength of rock，the surrounding rock collapsed into the arch shape. At the same time，the tangential stress in rock mass located within the collapse scope dropped sharply. This feature can be used to determine the range of collapsed rock mass. When tunnel was excavated，due to the barrier effect of fault，the rock mass stress within the hanging wall and footwall of fault presented the characteristics of discontinuous and nonlinear distribution.