深部硬岩矩形隧洞围岩板裂破坏的试验模拟研究

为了深入认识深部硬岩矩形隧洞围岩板裂破坏的发生机制，利用花岗岩材料加工含预制矩形孔洞（40 mm×40 mm）的立方体试样（100 mm×100 mm×100 mm），并采用TRW?3000岩石真三轴电液伺服诱变试验机进行了模拟试验研究。模拟试验中首先以深部1 000 m的地应力条件作为初始加载应力状态，保持孔洞径向和轴向的水平向应力不变，然后在竖直向加载直至孔洞两侧洞壁围岩发生破坏，并保证试样整体始终处于稳定状态。加载过程中利用岩样内部结构破坏实时视频监控系统,进行全程的实时记录和监测。试验结果表明，在竖直向为最大主应力和水平轴向为中间主应力的情况下，矩形孔洞两侧洞壁围岩整体发生明显的板裂破坏，破坏区域呈对称状，而顶板和底板始终保持稳定状态。侧壁围岩的破坏方向平行于竖直向，呈现典型的张拉板裂状破坏特征。整个破坏过程划分为平静期阶段、洞壁两侧上下肩角处颗粒弹射阶段、侧壁围岩裂纹扩展阶段和裂纹贯通板裂破坏阶段。当进入到裂纹贯通板裂破坏阶段时，无论是加载还是保载过程，板裂破坏都可能持续发展。试验过程中，试样洞壁两侧围岩的板裂破坏整体上呈现静态破坏模式，而且破坏区域沿水平方向逐渐向洞壁深部发展，最终形成沿轴向的贯穿型对称弧形槽。

Simulation experimental study of spalling failure of surrounding rock of rectangular tunnel of deep hard rock

This study is aimed to investigate the spalling failure mechanism of surrounding rock in the rectangular tunnel of deep hard rock. A cubic granite specimen (100 mm×100 mm×100 mm) was prepared with a precast rectangular hole (40 mm×40 mm), and then the simulation test was carried out by using the TRW-3000 true triaxial electro-hydraulic servo mutagenesis testing machine. In the simulation test, the in-situ stress of the depth of 1 000 m was selected as the initial loading stress state, and the horizontal stresses of the rectangular hole were kept constant in the radial and axial directions. After that, the vertical loading was applied until the surrounding rock on both sidewalls of the hole was destroyed, and the whole specimen remained in a stable state. During the loading process, a real-time video surveillance system was employed to monitor the failure process of the internal structure of the rock specimen. The results showed that when the maximum principal stress was at the vertical direction and the intermediate principal stress was at the horizontal axis, the obvious spalling failure appeared on the surrounding rock of both sidewalls of the rectangular hole. Moreover, it was found that the failure zone of the surrounding rock was symmetrical, whereas the roof and the floor remained stable. Meanwhile, the failure of surrounding rock was parallel to the vertical direction, showing typical tensile cracking and spalling characteristics. The entire failure process was divided into the calm stage, the particle ejection stage on the shoulder angles of the hole, the sidewall crack propagation stage and the crack penetration spalling stage at both sidewalls. When entering the crack penetration spalling stage, the spalling failure may continue to develop regardless of the loading or load-holding process. During the test, the spalling failure of the surrounding rock on the both sidewalls of the specimen presented a static failure mode. Besides, the failure zone gradually developed towards the deep part of the wall along the horizontal direction, and finally formed a penetrating symmetric arc notch along the axial direction.