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

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 2 525 m, more than 75% of the buried depth is more than 1 500 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. © 2020, Science Press. All right reserved.