Research On Leading Pre-supporting Technology In Large-cross And Shallow Weak-surrounding Rock Tunnels

With the economic development of our country, transportation flow has gradually increased, and the existing road cannot meet the ever increasing demand of transportation. To speed up the highway and railway construction to solve traffic problems in our country has become a key link. One of the important parts in the highway and railway construction is tunnel construction. The paper using the under-construction chenjiapo tunnel of chengdu-chongqing high-speed railway as research underground, and with methods of theoretical analysis、numerical simulation and field testing analysis make a study on advanced support of large cross-section shallow buried soft rock tunnel. The main research contents are as follows:①Studied in large-cross and shallow tunnel,compared the commonly used methods in advanced support of soft rock tunnel, such as,pipe shed advanced support、leading conduit、 mechanical pre-cutting method、curtain grouting and deep-hole grouting. And analyzed the support mechanism、application conditions、application range、advantages and disadvantages.②Taking a working project of chenjiapo tunnel,a part of chengyu high-speed railway line,as an example,though the comprehensive analysis of chenjiapo tunnel on geolo gical of the tunnel、hydrological conditions and construction environment,etc. A scheme of pre-grouting strengthening support with leading conduit is given,and detailed study on key construction process of primary support、secondary lining and waterproof and drainage construction has been made.③Making dynamic construction simulation on tunnel construction process with the general finite element analysis ANSYS. Analysed the results of the two model, one is pre-grouting strengthening support with leading conduit, the other is pre-grouting strengthening support with non-leading conduit,and compared them in ground settlement、 crown settlement、clearance convergence and data on stress of the surrounding rock, to get the remarkable effect of pre-grouting strengthening support with leading conduit.④Through the actual measurement, monitoring on ground settlement、crown settlement、clearance convergence, in the chenjiapo tunnel construction process, comparative analysis of monitoring data and simulation data,further verify the feasibility of ahead of the small pipe grouting pre-reinforcement programand stability...