Time-Dependent Deformation Behavior of Completely Weathered Granite Subjected to Wetting Immersion

As a common lithology material of tunnel surrounding rock, rock mass in fault fracture zones is often wetted by groundwater to produce extensive wetting-induced deformation, which threatens the long-term stability of underground engineering. To investigate the wetting-induced deformation behavior of such surrounding rock mass and to explore effective maintenance and control techniques, the strength and wetting deformation characteristics of completely weathered granite from a tailrace tunnel to be excavated in the fault fracture zones were studied using a large-scale triaxial shear apparatus. Under the same confining pressure, the natural and saturated specimen strengths were slightly different, but their deformations were very different, especially under low confining pressures. After wetting, the wetting-induced deformation of the specimens was affected mainly by confining pressure and stress level, and the deformation was more sensitive to the stress level than the confining pressure. The wetting-induced deformation process presented significant time-dependent characteristics with stable creep. A new time-varying effect model was established based on the experimental results, which enabled an accurate simulation of the wetting deformation of the rock mass through a comparison with the experimental results. A criterion to judge the deformation stability of such surrounding rock was proposed from the perspective of an engineering application. These results allow for further study of the deformation mechanism and control measures for underground deformation by wetting.

Automated summary

This study investigated the wetting-induced deformation behavior of rock mass in fault fracture zones, and established a new time-varying effect model for accurate simulation of the wetting deformation. A criterion for judging the deformation stability of such surrounding rock from an engineering perspective was proposed based on the experimental results.