Influences of structural variation of host rock induced by engineering activities on water inrush of tunnels

Water inrush disasters have become a serious problem resulting from the current trend that numerous traffic roads and hydropower tunnels are constructed, and minerals are mined in deep underground. The variation of rock structures induced by engineering activities has great influences on the mechanical and hydraulic properties of the host rock, and the seepage fields around tunnels. The theoretical analysis method is employed to investigate the influences of the structure variation of rock on the groundwater inflow rate and pore water distribution based on the damage and permeability evolutions of host rock induced by engineering disturbance. The results show that the influences of the thickness of the damage zone on the pore water distribution and the groundwater inflow rate are significant. The risk of water inrush increases with the increase of the thickness of the damage zone. The influences of the hydraulic conductivity on the pore water distribution and the groundwater inflow rate are weak if more than two orders of magnitude increase in hydraulic conductivity of damaged zone. The inflow rate decreases with the increase of the thickness of grouting circle and the decrease of its hydraulic conductivity. However, there is a best design value for the thickness and permeability of the grouting circle, rather than the effect of greater thickness and lower permeability of the grouting circle.