The effects of hydro-mechanical coupling in fractured rock mass on groundwater inflow into underground openings

The effects of hydro-mechanical coupling in fractured rock mass on groundwater inflow into underground openings were investigated using numerical simulations and case study. The groundwater inflow were obtained with different stress field configuration, fracture shear dilation behavior and fracture orientations The interplay of stress field configuration and fracture orientation on both fracture aperture change and groundwater inflow were identified. It was found that the rock fractures could be closing or opening due to the excavation of underground openings. The contributions of initial aperture, stress redistribution and shear dilation to final fracture aperture were decomposed under different conditions. It was shown that for the cases with lateral coefficient less than unity, the groundwater inflow distribution is correlated to stress redistribution; while for the cases with lateral coefficient greater than unity, the groundwater inflow distribution is correlated to shear dilation. An improved prediction equation for groundwater inflow was proposed with a synthetically consideration on the effects of hydro-mechanical coupling on groundwater inflow. The equation was verified against the field measurement of groundwater inflow into underground oil storage facility in granitic rock mass.