The essence of roadway excavation is a process of unloading at the periphery, and the influence of unloading paths on surrounding rock damage is directly related to the selection of support design and construction technology. The real stress state of surrounding rock is often affected by different excavation conditions in the actual construction process. Therefore, a testing system of excavation and unloading model was developed to simulate the unloading process of the arch roadway under different excavation conditions. Small hollow cylindrical specimens used in this experiment were made of cement mortar. The load at the inner cavity of specimens was removed under the constant action of external pressure and axial force to simulate the real excavation unloading process. The deformation, the failure modes, and the acoustic emission evolution characteristics at the inner of specimens were obtained under unloading conditions using the strain and acoustic emission monitoring systems. The experimental results indicate that deformation laws of surrounding rock were similar under different unloading rates and initial geostresses, but failure modes and acoustic emission characteristics were quite different. Compared with that of slow unloading, the damage of surrounding rock under rapid unloading mainly accumulated after unloading, and it is easier to induce rockburst after unloading. As initial geostress increased, the occurring time of the main fracture may be delayed relatively, and the phenomenon that the distribution range of peak frequency expanded and the amplitude rose gradually can be regarded as the precursor information of the main fracture occurring. This study can be used to provide experimental support for the failure and supporting design of surrounding rock in deep underground engineering.

中文翻译：

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不同卸荷率下拱形巷道变形与声发射特性试验研究

巷道开挖的实质是在外围进行卸荷的过程，卸荷路径对围岩破坏的影响与支护设计和施工工艺的选择直接相关。在实际施工过程中，围岩的实际应力状态往往受开挖条件的影响。因此，开发了一套开挖与卸载模型测试系统，以模拟不同开挖条件下拱形巷道的卸载过程。本实验中使用的中空圆柱形小试样由水泥砂浆制成。在外部压力和轴向力的恒定作用下，去除试样内腔的载荷，以模拟实际的开挖卸载过程。变形，破坏模式，并利用应变和声发射监测系统在卸载条件下获得了样品内部的声发射演化特征。实验结果表明，在不同卸荷率和初始地应力作用下，围岩变形规律相似，但破坏模式和声发射特性差异很大。与缓慢卸载相比，快速卸载下的围岩破坏主要是在卸载后积累的，卸载后更容易引起岩爆。随着初始地应力的增加，主裂缝的发生时间可能会相对延迟，峰值频率的分布范围扩大，振幅逐渐上升的现象可以看作是主要裂缝发生的前兆信息。该研究可为深部地下工程围岩的破坏及支护设计提供实验支持。