Analysis Method And Engineering Application Of Surrounding Rock Stability Of Deep-Buried Tunnel Under High External Water Pressure

With the implementation of the strategy of marching deep into the earth,there are more and more projects in the fields of water conservancy and hydropower,transportation,energy mining and national defense engineering.With the increase of tunnel depth,high external water pressure has become an important factor affecting the safety of the tunnel,which has a very adverse impact on the excavation and support of the tunnel and the safety of the tunnel during operation.It often causes disasters such as water and mud inrush,collapse and roof fall in the tunnel,resulting in huge economic losses and a large number of casualties of construction workers.Therefore,the analysis research of surrounding rock stability of deep-buried tunnel under high external water pressure can provide scientific guidance for the design optimization of deep tunnel and ensure the economy and safety of engineering construction..This paper took Xianglushan tunnel in Central Yunnan water diversion project as the research background,and studied the nonlinear deformation law of surrounding rock and the distribution law of external water pressure of deep-buried tunnel under the action of high ground stress and high seepage pressure by means of indoor test,model test,theoretical analysis and numerical simulation.The true three-dimensional geomechanical model test of Xianglushan tunnel construction simulation under the coupling of stress field and seepage field was carried out,the stress non-Darcy flow coupling analysis mechanical model considering the change of permeability coefficient was established,and the three-dimensional numerical analysis program of deep tunnel under high external water pressure was compiled.The pressure relief measures of external water pressure and anti-seepage control measures of deep-buried tunnel lining were analyzed.The main achievements of this paper are as follows:(1)The seepage mechanical tests of deep surrounding rock of Xianglushan tunnel under different confining pressures and seepage pressures were carried out.The nonlinear deformation strength characteristics,seepage mechanical characteristics and deformation failure mode of deep surrounding rock were revealed,and the nonlinear softening model considering seepage pressure and the empirical equation of surrounding rock permeability change were established.(2)The three-dimensional model test system of the deep tunnel under hydro-mechanical coupling and the new-style hydro-mechanical coupling similar material were independently developed.The true three-dimensional physical simulation test of Xianglushan tunnel construction simulation under hydro-mechanical coupling was carried out.The engineering geological conditions and the dynamic construction process of tunnel excavation and support were truly simulated.And the variation laws of surrounding rock stress,deformation,lining contact pressure and seepage pressure during tunnel construction were obtained.The coupling mechanism of stress field and seepage field in surrounding rock of deep tunnel was revealed,which provides scientific guidance for mechanical modeling and numerical analysis.(3)Based on the Hoek Brown criterion and the non-Darcy flow motion equation,a stress non-Darcy flow coupling analytical mechanical model considering the change of permeability coefficient was established.Based on the typical tunnel section of Xianglushan tunnel of central Yunnan water diversion project,the analytical calculation and analysis of the tunnel under the conditions of different lining thickness,different lining permeability coefficients and different groundwater heads were carried out.And the nonlinear deformation law of surrounding rock and the distribution law of external water pressure of deep tunnel under high ground stress and high seepage pressure were revealed.(4)According to the established mechanical model of stress non-Darcy flow coupling analytical mechanical model considering the change of permeability coefficient,a three-dimensional numerical calculation and analysis program for hydro-mechanical coupling of deep-buried tunnel under high external water pressure was compiled based on ABAQUS.The reliability of the calculation and analysis program was verified by seepage mechanics test.(5)Based on Xianglushan tunnel in Central Yunnan water diversion project,using the established three-dimensional numerical calculation and analysis program for hydro-mechanical coupling of deep-buried tunnel under high external water pressure,the influence laws of different underground water heads,lining permeability coefficients and lining thickness on tunnel stability were revealed through numerical calculation.And the anti-seepage control measures considering the influence of grouting layer thickness,permeability coefficient of grouting layer,the number and depth of drainage holes were put forward.