Research on Change Law of the Outer Water Pressure and Lining Stress Caused by Blockage of Drainage Blind Pipes in Railway Tunnels
In order to explore the change law of water pressure outside the lining caused by the blockage of tunnel drainage blind pipes and its influence on tunnel structure,a three-dimensional numerical model of the tunnel is established by FLAC3D software.Using the permeability coefficient reduction method to simulate different clogging degrees of drainage blind pipes,this paper studies the water pressure and its main stress change law on the outside of the tunnel lining under different working conditions such as different water level height,different degree of blockage of drainage blind pipes,different continuous blockage length and asymmetric blockage.The results show that under different water level heights,the overall circumferential water pressure of the tunnel periphery is the largest at the arch bottom and the smallest at the arch foot,and the maximum(small)principal stress change of tunnel lining increases with the rise of water level,among which the main stress change of lining at the arch foot is the most significant.When the drainage blind pipes are blocked,the water pressure of different parts of the outer part of the lining increases accordingly,and the water pressure increase at the arch foot is the largest.When the degree of blockage exceeds 50%,the increase rate of water pressure is significantly accelerated,and the growth rate is most obvious at the foot of the arch,which indicates that the adverse effects caused by the blockage of the drainage blind pipes do not increase linearly with the deepening of the degree of blockage.When the drainage blind pipes with a distance of 8 m on both sides of the tunnel are blocked for more than 16 m,the maximum water pressure on the outside of the vault lining of the blockage section reaches 92%when it is fully blocked,so it is recommended that when more than 2 consecutive blockages are blocked at the outlet of the longitudinal drainage blind pipes of the railway tunnel,the blocked drainage pipe should be dredged in time.The bias phenomenon of the tunnel occurs after the asymmetrical blockage of the drainage blind pipes,and the outer water pressure and lining main stress on the blocked side are significantly increased compared with those under the normal drainage conditions.The research results can provide some reference for the service status assessment and treatment of tunnel drainage blind pipes.
railway tunneldrainage blind pipeblockage simulationlining water pressurelining stress
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