Analysis Of The Influence Of Drainage Scheme On External Water Pressure And Internal Force Of Tunnel Lining In High Pressure And Water Rich Karst Areas

The height of water head in karst area may be as high as 100 meters.In order to avoid destruction of tunnel lining caused by high water pressure in operation period,reasonable drainage scheme should be adopted to reduce external water pressure and internal force of tunnel lining.In this paper,Jiajiaoshan tunnel of Chengdawan High-speed Railway is taken as the engineering background and numerical simulation is adopted to study the influence of different drainage schemes on external water pressure and internal force of lining.The main work and achievements are as follows:(1)The influences of drainage flow rate of parallel heading,horizontal distance and vertical distance between parallel drift and tunnel on the external water pressure and internal force of lining under the condition of full tunnel sealing are studied,and the influences of displacement of parallel drift,flow rate of tunnel,grouting ring thickness and permeability coefficient on the external water pressure and internal force of lining under the condition of coordinated drainage of parallel drift and tunnel.The study shows that: In the case of fully blocked drainage scheme,increasing the discharge of parallel drift has a certain effect on reducing the external water pressure and internal force of lining.In the case of low initial water level in karst area,the fully blocked drainage scheme is feasible.In the case of coordinated drainage of parallel drift and tunnel scheme,Increasing the thickness of the grouting ring,reducing the permeability coefficient of the grouting ring and increasing the allowable displacement of the tunnel can effectively reduce the external water pressure and internal force of the lining,and under the condition of high initial water level,the scheme is more feasible.(2)The stress on both sides of the lining is uneven because of the drainage of the parallel drift,under the condition of water blocking and drainage limitation.Based on this,In this paper,the influences of different grouting ranges on the external water pressure and internal force of the lining are compared.The results show that increasing the grouting ring thickness of the tunnel far away from the parallel drift can help improve the bias pressure on both sides of the lining,and save the grouting material on the premise of ensuring the safety of the lining.(3)The ultimate head height of single-line and double-line standard section tunnel lining in level 5 surrounding rock under different drainage schemes is studied.The results show that: When the tunnel is fully blocked,increasing the drainage flow of the parallel drift has a certain effect on improving the limit head of the tunnel,but the effect is limited.When the tunnel is blocked and drained,the limit head of the tunnel can be significantly improved by increasing the allowable displacement of the tunnel.Under the two drainage methods,the double-line tunnel has better resistance to high water pressure than the single-line tunnel.