深埋硬岩隧洞开挖响应合理解译与监测优化

Reasonable interpretation and monitoring optimization on excavation response of deep buried tunnel in hard rock

在地下工程建设过程中,为及时了解围岩状态及其决定的支护型式,需要依赖于有效的监测方法和可靠的监测数据。锦屏二级深埋隧洞沿线以硬脆性大理岩为主,最大埋深达到2525m,75%以上洞段埋深超过了1 500 m,在如此复杂的地质环境下开挖14m的大跨度隧洞,面临着巨大的工程风险,而监测方法的针对性和指示性与浅埋条件下存在较大差异。大理岩的压缩试验和现场开挖响应都揭示了完整大理岩开挖以后的主要响应不是变形,而是破裂。通过对锦屏二级深埋隧洞的变形、应力和声波测试成果的深入解译,表明围岩破坏时变形仍可能在围岩变形的控制标准范围之内,变形监测失去了预警的意义,而锚杆应力计对围岩状态的变化比多点位移计更加敏感,更具有预警价值,声波测试成果也与锚杆应力监测成果具有很好的一致性。最后,利用数值方法对围岩内部的应力状态进行详细描述,利用大理岩的脆–延–塑转换特征可以合理地解释变形与破裂之间的矛盾关系。

In order to understand the state of surrounding rock timely and support type,it is necessary to depend on effective monitoring methods and reliable monitoring data in the process of underground engineering construction.Jinping II deep buried tunnel is given priority to brittle marble.The maximum depth is 2525 m,more than 75%of the buried depth is more than 1500 m.A large tunnel of 14 m diameter is excavated in such a complex geological environment,will face with the huge project risk.The target and indicative of monitoring method is difference from the shallow condition.The compression test and excavation response showed the main response after excavation of complete marble is not deformation,but fracture.A thorough interpretation was carried on deformation,stress and sound wave test result of Jinping II deep buried tunnel.Research results show that when the surrounding rock is failure,the deformation may still in the range of surrounding rock deformation control standards.The deformation monitoring has lost the significance of early warning,and the anchor stress meter is more sensitive on the state of the surrounding rock than multi–point displacement meter,and has more warning value.The acoustic test results were well consistency with anchor stress monitoring results.Finally,the numerical method was used to describe the internal stress state of surrounding rock in detail,and the brittle–ductile–plastic conversion characteristic of marble can reasonably explain the contradictory relationship between the deformation and fracture.