Analysis of Stability of Tunnel under Two-dimension Unequal Pressure in High Water Pressure Area

Research purposes: In high water pressure area,the tunnel is easy to collapse and water inrush occurs because of groundwater seepage,which makes the secondary stress state of the excavated tunnel changed and thus the inelastic deformation area around the tunnel is altered. In this paper,stress distribution and factors that affected the plastic zone and the rupture zone of surrounding rock of the tunnel under ground water are analyzed to provide evidence of decision making for the maintenance of tunnel in high-pressure water-rich area.Research conclusions:( 1) Taking into account seepage body force,strain softening of rock mass,dilatancy and lateral pressure coefficient,elastic-plastic mechanics theory is applied to derive distribution laws of stress and displacement of surrounding rock under two-dimension unequal pressure considering seepage,strain softening and dilatancy,and establish relationships between different partition range of surrounding rocks,pore water pressure,strain softening coefficient of rock mass,dilatancy factor and lateral pressure coefficient.( 2) The results have shown that pore water pressure,lateral pressure coefficient,strain softening of rock mass and dilatancy have greater impact on the fractured zone than the plastic zone. Considering lateral pressure coefficient,the impact of seepage field,strain softening of rock mass and dilatancy on the plastic zone and the fractured zone of tunnel along the different directions show inhomogeneity.( 3) The results provided a theoretical basis for the stability analysis on surrounding rock of tunnel in high water pressure area. And it is practical meaningful for underground engineering like supporting structure design of the tunnel in the high-pressure water-rich area and decision of the scope of the pre-grouting works.