Research On Water Gushing Mechanism And Key Construction Technology Of Water Rich Fault Tunnel

With the rapid development of China’s transportation infrastructure,tens of thousands of kilometers of transportation tunnels are being or will be built in areas with extremely complex terrain and geological conditions.In the process of tunnel construction,water inrush,mud inrush,large deformation of soft rock,rock burst,ground subsidence and other disasters are often encountered.Among them,water inrush is the most prominent phenomenon,which has become one of the important problems affecting the construction period,causing heavy casualties,economic losses and serious ecological environment damage.Based on the HONGTU extra long tunnel project,aiming at the large-scale water gushing phenomenon in tunnel construction,Methods of investigation and analysis,theoretical derivation,numerical simulation and indoor test are adopted to carry out the analysis of water gushing factors,prediction of water gushing volume,evolution of seepage field and displacement field in the construction of crossing fault Zone,and water gushing treatment measures in this paper.The main work and research results are as follows:(1)Based on the engineering geological and hydrogeological conditions of HONGTU extra long tunnel,this paper analyzes the influence of topography,stratum lithology,geological structure and other factors on the tunnel water inflow,reveals the structural distribution characteristics of the fault zone,and lays a foundation for the prediction of water inflow and the study of the seepage and deformation laws of the tunnel crossing the fault zone.(2)The theoretical analytical formula of tunnel water inflow is deduced.The calculation method of sectional water inflow based on analytic method is proposed.The excavated part of the tunnel is divided into different catchment zones and hydrogeological characteristics.The water inflow in each section is calculated separately and the collected water inflow is used as the pre measured water inflow.The accuracy of different calculation methods is compared and analyzed.(3)Through numerical simulation software,the variation of pore water pressure field and displacement field under different construction measures is analyzed.Based on this,the influence of tunnel excavation on pore water pressure field and displacement field under different fault dip angle,surrounding rock permeability,fault zone permeability,grouting effect and support permeability is considered by using orthogonal test analysis method,Reasonable suggestions are put forward for tunnel construction.(4)Based on HONGTU extra long tunnel,the research on advanced curtain grouting technology and strong bond shotcrete initial support technology is carried out.Through indoor test,the proportioning parameters of grouting material and shotcrete are put forward,which are applied in tunnel water plugging construction,and the working environment in the process of tunnel construction is improved.