In this study, a new strain burst test system was used to conduct two types of strain burst experiments by rapidly unloading single and double faces (in one direction), to simulate the strain burst occurring in surrounding rock of tunnel or double tunnel faces during the opposite tunneling. A high-speed image recording system and an acoustic emission system were used to monitor the failure process of strain burst of red sandstone. The commonalities of these two types of strain burst are as follows: failure stress and percentage of dissipation energy due to crack propagation were approximately equal; the evolution of mean velocity of free face was similar, which suddenly increased first and then decreased, then the gradient increased to the extremum value, and finally decreased to zero. Subregions of the fracture were consistent, and both showed shear, buckling, splitting, and ejection zones. However, the strain burst intensity for unloading double faces was larger than that for unloading single face, as demonstrated by a larger initial ejection velocity, larger volume of burst pit, and lower peak frequency. Furthermore, when double faces were unloaded, the flaky and massive features of fragments obtained due to strain burst were more obvious than the fragments obtained from the unloading of single face. Moreover, from yield to burst, when double faces were unloaded, the sandstone strain burst contained more shear microcracks, whereas the strain burst when unloading single face contained more tensile microcracks.

中文翻译：

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真三轴加载和双面单向卸载砂岩应变爆破特性试验研究

本研究采用一种新型应变爆破试验系统，通过单面和双面（一个方向）快速卸荷两种应变爆破试验，模拟隧道或双隧道工作面围岩发生的应变爆裂。对面隧道。采用高速图像记录系统和声发射系统对红砂岩应变爆破破坏过程进行监测。这两种应变爆裂的共同点如下：裂纹扩展引起的破坏应力和耗散能量百分比近似相等；自由面平均速度的演化也类似，先增大后减小，然后梯度增大到极值，最后减小到零。骨折的亚区是一致的，并且都显示剪切、屈曲、分裂和顶出区。然而，卸载双面的应变爆发强度大于卸载单面的应变爆发强度，表现为更大的初始弹射速度、更大的爆坑体积和更低的峰值频率。此外，在双面卸载时，应变爆破碎片的片状和块状特征比单面卸载的碎片更明显。此外，从屈服到爆裂，当双面卸载时，砂岩应变爆裂包含更多的剪切微裂纹，而单面卸载时的应变爆裂包含更多拉伸微裂纹。正如更大的初始喷射速度、更大的爆坑体积和更低的峰值频率所证明的那样。此外，在双面卸载时，应变爆破碎片的片状和块状特征比单面卸载的碎片更明显。此外，从屈服到爆裂，当双面卸载时，砂岩应变爆裂包含更多的剪切微裂纹，而单面卸载时的应变爆裂包含更多拉伸微裂纹。正如更大的初始喷射速度、更大的爆坑体积和更低的峰值频率所证明的那样。此外，在双面卸载时，应变爆破碎片的片状和块状特征比单面卸载的碎片更明显。此外，从屈服到爆裂，当双面卸载时，砂岩应变爆裂包含更多的剪切微裂纹，而单面卸载时的应变爆裂包含更多拉伸微裂纹。