Research On Water Gushing Mechanism And Drainage System Of Extra-long Tunnel With Rich Water In Lianhua Mountain Regional Fault Zone

The surrounding rock of extra-long tunnel with rich water in fault zone has been in a complex seepage and stress coupling environment for a long time.Meanwhile,the geological structure and hydrological environment are complex,and the risk of water inrush in the tunnel is high.For the research of tunnel water inrush disaster,scholars have carried out a lot of investigation,test and analysis research work,and the results have promoted the development of design and construction of subsea tunnel and tunnel in water rich area of homogeneous surrounding rock.However,the research on water inrush disaster of fault water rich mountain tunnel has not formed a very mature theoretical system so far,and its application is limited to a certain extent.Based on the Hongtu Extra-long Tunnel,a systematic research on the water gushing mechanism and drainage system of extra-long tunnel with rich water in Lianhua Mountain regional fault zone is carried out by means of literature survey,model test,remote sensing monitoring,numerical simulation and theoretical analysis,aiming to provide technical support and guarantee for the safe construction and operation of water-rich tunnels in fault areas.The main research contents and achievements are as follows:(1)Based on the established unified coordinate system,the cutting relationship between the fault and Hongtu Tunnel was clarified.The water inflow recharge source of the tunnel was studied by using the measured water inflow and field test,and the water inflow calculation model of the water rich tunnel in the fault zone was constructed.Based on the hydraulic theory and the law of conservation of fluid mass,the calculation formula of water inflow in a water-rich tunnel in the fault zone was derived.The validity of the constructed model and the correctness of the water inflow calculation formula were verified through degradation analysis and field tests,and the water inflow mechanism and influence characteristics of water-rich tunnel in fault zone were discussed.(2)The influences law of tunnel water gushing,influenced by dispersion of permeability caused by burial depth and excavation disturbance,tunnel face disturbance,and ground water level drops caused by water gushing,were revealed.The influence characteristics of various factors on water inflow were further discussed,and the prediction accuracy of water inflow was improved.Considering the influence of buried depth and excavation disturbance on the permeability of surrounding rock,the calculation accuracy of water inflow can be significantly improved;the water inflow calculated by three-dimensional flow near the tunnel face is relatively close to the field measured value;the predicted water inflows are consistent with the numerical simulation results when the groundwater level drops due to drainage is considered.(3)The influence law of circumferential blinded-pipe intervals on tunnel water inrush was analyzed;the influence mechanism of drainage system blockage on tunnel water inflow was systematically studied;a simplified calculation model of tunnel water inflow considering the drainage system was constructed;the working principle of the drainage system was revealed;the failure mechanism of drainage system was discussed;the characteristics of influencing factors of external drainage system were clarified;the design theory of drainage system was optimized,which all effectively guided the design and construction of the drainage system.(4)The stress and deformation characteristics of the rock mass in front of the tunnel face were revealed when the tunnel passed through the fault zone;the calculation model of the minimum safe distance of the tunnel face when the tunnel passed through the fault zone was constructed;the calculation formula of safety distance was deduced;the timing of water gushing disaster disposal in water-rich tunnels in the fault zone was determined;based on the elastic-plastic theory,the elastic-plastic stress solution and the calculation formula of the plastic zone were deduced when the buffer layer was set;the grouting reinforcement technology for the outer ring of the surrounding rock was developed;the influence law of grouting materials on grouting reinforcement effect was analyzed,and the grouting reinforcement design system was optimized.(5)The interaction mechanism between water inflow and surface environment in Hongtu Tunnel during construction and operation was revealed;the tunnel water discharge standard was determined;based on remote sensing monitoring and manual reconnaissance,the impact characteristics of Hongtu tunnel water inrush on the surrounding environment were analyzed;the surface water bodies and vegetation around the tunnel were effectively protected;the validity of the research on the mechanism of water inflow and water-proofing and drainage of the water-rich and extra-long tunnels in the Lianhua Mountain regional fault zone was verified.