Analysis Of Surrounding Rock Stability And Water Inflow Prediction For Shield Tunneling Through Dalian Bay

With the explosive growth of the national economy and the accelerated development of China's transportation construction,the demand for the construction of subsea tunnels in coastal cities has also increased.Compared with the mountain tunnel,the hydrogeological conditions of the subsea tunnel project are relatively complex and have many unknowns.The surrounding rock of the submarine is in the state of high pressure water head and unlimited seawater recharge at the moment,and the submarine tunnel has difficulty in survey and low precision and other technical difficulties.The shield tunnel construction process of the subsea tunnel is a process that continuously disturbs the surrounding rock of the tunnel.Once the instability of the surrounding rock of the submarine tunnel will induce tunnels to collapse,water inrush,water inflow,and other major safety accidents.Therefore,before the construction of the subsea tunnel,the risk of surrounding rock instability and maximum water inflow forecast should be carried out to ensure the safe and reliable construction of the subsea tunnel.Based on the analysis of the research results in the field of construction safety of a large number of tunnel shields,relying on the reality of shield tunnelling in the Dalian Bay subsea tunnel of Dalian Metro Line 5,theoretical analysis and numerical simulation methods are used to stabilize the surrounding rock during the construction of shield tunnels in a subsea tunnel.Based on the analysis of the laws of the nature and seepage fields,and on this basis,the water inflow from the sub-sea tunnels in this section is predicted.The main research work is as follows:(1)Reviewed domestic and international research work on the stability analysis of surrounding rock,seepage field,prediction of water inflow from tunnels,and research on safety were reviewed.The hydrogeological conditions of the Dalian Bay subsea tunnel were investigated on site,and the The data were collected,analyzed,and organized.The process,advantages and disadvantages of shield construction are analyzed.Based on this,the influence of karst geological conditions on the construction of Dalian Bay subsea tunnel was studied.The specific safety accident measures for the hydrogeological Characteristics of Dalian Bay were given.(2)The seepage model and the seepage model for grouting reinforcement of subsea tunnels without grouting were established.The water inflow and the pressure equations behind the lining were deduced on this basis,and calculations were performed using the Dalian Bay subsea tunnel as an example.The relationship between the water inflow in the Dalian Bay subsea tunnel and the parameters of the grouting circle was studied.(3)The FLAC3D is used to establish a Numerical Simulation Model of Shield Tunnel in Dalian Bay.Analysis of surrounding rock deformation,sea-bed settlement,deformation of shield segments,and pore water pressure redistribution during shield excavation,and the numerical simulation data and the actual monitoring data are compared and analyzed,and the rationality of the numerical simulation process is verified.(4)Summed up the method for predicting the water inflow from subsea tunnels.Through theoretical calculations and numerical simulations,the prediction and comparative analysis of the water inflow in the Dalian Bay subsea tunnel was conducted.Some research results with guidance on construction safety were obtained.This will provide guidance for the future construction of the shield tunnel of Dalian Bay subsea tunnel and similar projects.