Significant differences in the failure characteristics of surrounding rocks caused by complex lithologies and geological conditions have been observed in deep tunnels. In this work, a failure involving rockburst and collapse observed in a deep tunnel excavated by a tunnel boring machine (TBM) was introduced. The in-situ failure characteristics of granite with biotite interlayers with different biotite contents and particle sizes were studied via field investigations and mineral composition analysis. The microseismic activity characteristics and fracture mechanisms at different failure zones were analyzed. The strength, failure, acoustic emission (AE) and brittleness characteristics of these types of granites were studied via true triaxial compression tests. The results showed that the biotite granite with biotite interlayers is prone to rockburst and that high-intensity rockburst may occur with less energy than in the intact biotite granite area. The rock fractures are mainly tensile failures, even in the biotite interlayer area. In contrast, the feldspar biotite schist surrounding rock is prone to collapse regardless of whether it contains biotite interlayers. The number of microseismic events during this collapse is relatively small, but the energy is relatively high compared with that of the rockburst at the biotite granite with biotite interlayers. The true triaxial strength and brittleness of the granite samples gradually decrease with increasing biotite content. The biotite granite exhibits very high AE activity, so it is prone to rockburst. The AE activity of medium-coarse grained monzogranite is relatively low; thus, both rockburst and collapse may occur. The strength, brittleness, and AE activity of feldspar biotite schist are very low, and its failure mode is mainly collapse. This study elucidates the typical failure modes and characteristics of different granites with biotite interlayers and can provide a basis and guidance for targeted failure warning and mitigation in tunnels with similar lithologies and geological conditions.

中文翻译：

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隧道中穿过花岗岩和黑云母夹层的围岩破坏特征的原位和实验研究


在深隧道中观察到复杂岩性和地质条件引起的围岩破坏特征存在显著差异。在这项工作中，介绍了在隧道掘进机 （TBM） 开挖的深隧道中观察到的涉及岩爆和坍塌的破坏。通过野外调查和矿物成分分析，研究了不同黑云母含量和粒径的黑云母夹层花岗岩的原位破坏特征。分析了不同破坏区的微震活动特征和断裂机制。通过真正的三轴压缩试验研究了这些类型花岗岩的强度、破坏、声发射 （AE） 和脆性特性。结果表明，黑云母与黑云母夹层的黑云母花岗岩容易发生岩爆，并且与完整的黑云母花岗岩区域相比，高强度岩爆的能量可能发生。岩石裂缝主要是拉伸破坏，即使在黑云母夹层区域也是如此。相比之下，长石黑云母片岩围岩无论是否包含黑云母夹层，都容易坍塌。这次崩塌过程中的微震事件数量相对较少，但与黑云母花岗岩与黑云母夹层的岩爆相比，能量相对较高。花岗岩样品的真三轴强度和脆性随着黑云母含量的增加而逐渐降低。黑云母花岗岩表现出非常高的 AE 活性，因此容易发生岩爆。中粗粒二长花岗岩的 AE 活性相对较低;因此，岩爆和坍塌都可能发生。 长石黑云母片岩的强度、脆性、声发射活性都很低，其破坏模式以塌陷为主。本研究阐明了具有黑云母夹层的不同花岗岩的典型破坏模式和特征，可为相似岩性、地质条件的隧道中有针对性的破坏预警和缓解提供依据和指导。