Research On Thickness Of Anti-outburst Rock Pillar Of Tunnel Lateral Cavity Based On Fluid-solid Coupling

Limestone strata are widely distributed in southwestern China,and the groundwater is abundant.A large number of karst caves are distributed in the surrounding rocks.If effective measures are not taken,it will bring greater risks to the construction and later operations.In this paper,the Xinshanshutuo tunnel is taken as the backing project.During the excavation of the Xinshanshutuo tunnel,there is a water-soluble cave laterally in the tunnel.Anti-burst pillar.In view of this,through the fluid-solid coupling calculation method,using FLAC^3D software for numerical simulation,a three-dimensional calculation model of the tunnel is established,and the influence of the water-soluble cave on the tunnel and the thickness of the anti-burst rock column between the cave and the tunnel are studied.Theoretical value and practical engineering significance.The main research contents and results are as follows:（1）Summarized and summarized the main reasons for the formation of karst in this area,the main form of karst,the commonly used detection and forecasting methods and treatment measures during the construction of the tunnel.（2）Establish a three-dimensional numerical model of the tunnel’s lateral karst caves,and study the three working conditions of the tunnel under different karst diameters,different karst water pressures,and different anti-burst rock column thicknesses.The variation law of the stress,displacement and axial bending moment of the characteristic points of the arch ring in different sections in the transverse and longitudinal directions.（3）Using the basic theory of strength reduction method,by reducing the surrounding rock parameters of the tunnel and performing fluid-structure coupling analysis,the displacement mutation is used as the instability criterion of the surrounding rock of the tunnel.The reduction factor at this time is the safety factor.The relationship between the diameter and safety factor of the karst cave and the thickness of the anti-outburst rock column was separately studied.It is also found that when the anti-burst rock column is unstable,the minimum principal stress also changes suddenly.（4）When the safety factor is 2,the orthogonal test is used to test the diameter of the cave,the water pressure of the cave and the thickness of the anti-outburst column.Using multiple regression analysis,the fitting function of the thickness of the anti-outburst column is obtained..It can provide a reference for the calculation of the thickness of anti-burst rock columns in similar projects.