Research on Advanced Pilot Tunnel Design of Squeezing Surrounding Rock Tunnel Based on Deformation Classification
The problem of large deformation of squeezing tunnel has always been a prominent problem that puzzles tunnel builders.Moderate release of surrounding rock stress can effectively control tunnel deformation.The advanced pilot tunnel is the most direct and effective stress release method.Based on this,considering the strength stress ratio,the grading standard of squeezing surrounding rock deformation is introduced,and FLAC3D software is used to simulate.Firstly,the influence of the ad-vanced pilot tunnel on the displacement and stress of the surrounding rock of the main tunnel in the standard double-line sec-tion of the railway tunnel under different deformation levels is studied.On this basis,the influence of advanced excavation dis-tance and section size on the deformation and stress of surrounding rock is further analyzed,and the recommended values of de-sign parameters of advanced pilot tunnel based on deformation classification are proposed.Finally,it is verified by practical en-gineering.The main conclusions are as follows:Regardless of the deformation grade,the standard double-line section of the rail-way tunnel can significantly reduce the deformation and stress of the surrounding rock of the main tunnel after the construction of the advanced pilot tunnel.The greater the deformation grade,the greater the reduction rate of displacement and stress,and the better the control of the deformation effect of the main tunnel.The larger the size and advance distance of the advanced pilot tunnel are,the more favorable the deformation control of the surrounding rock of the main tunnel is.However,when the advance distance is greater than 30 m or the area of the pilot tunnel is greater than 38 m2,the control of the displacement of the main tunnel will no longer be significant.
squeezing rockadvance pilot tunneldeformation gradationstress relief
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