Geo-mechanical model test on the collaborative bearing effect of rock-support system for deep tunnel in complicated rock strata

Abstract

Abstract Modern tunnel support design theory holds that surrounding rock not only generates load, but also takes load together with support system. However, how much loads will be taken by surrounding rock and support system respectively is still not clear. In order to investigate the cooperative effect of rock-support system for deep tunnel in complicated rock strata, we performed a true three-dimensional geo-mechanical model test to simulate tunnel construction crossing a weak fault based on the engineering background of Xianglushan Tunnel of Yunnan Water Diversion Project in China. Our test results reveal that: (1) the mechanical behavior of surrounding rock is influenced by the lithology. The evolution and distribution characteristics of displacement and stress are significantly different in various rock strata; (2) weak fault has little influence on the proportion of load taken by surrounding rocks, but has a distinct impact on the proportion of loads taken by supporting system components. Surrounding rock is the absolute dominant load-bearing body, taking about 97% of the excavation-induced load; (3) the bearing capacity of bolt is weak, and its main function is to reinforce surrounding rock. The lining is mainly used to bear load. Test results obtained in this study can provide important physical basis for the development of the construction scheme and the optimization of support design. These results can also serve as the benchmark for the validation of numerical models.