Study On Safety Of Lining Structure Of Mountain Tunnel Under Limited Discharge Mode

With the increase of the number of mountain tunnel projects and the exposure of leakage,technicians gradually realize that the important development direction of tunnel waterproofing and drainage system is water plugging and drainage.The popular saying is that the word "plugging" has leapt to the first place in the water-proof standard.The measures of water plugging in engineering are "preventing",injecting water,setting up waterproof layer,making waterproof curtain,making integral lining,refusing construction joint and so on.At the same time,researchers are constantly looking for breakthrough points,from the improvement of waterproof materials,innovation,to the building of waterproof structure.However,the existence of water has great unpredictability,its form of existence,the state of movement,changing,can not be prevented.Expansion joints,construction joints,such as the weakness of water permeability,but also add difficulty to the construction of drainage systems.In this paper,based on a limited drainage mode,the tunnel displacement is controlled by automatic regulation mechanism.The water pressure of the lining under the full drainage mode is relatively small,but the impact on the groundwater environment is great,and once the drainage system is blocked,the threat to the lining increases dramatically.The bearing capacity of compressive lining has upper limit,and a part of bearing capacity should be reserved as safety reserve for engineering safety consideration.In this controllable range,how to ensure the safety of lining,and to maximize the role of lining bearing capacity,is the focus of this paper.The main contents of the study are as follows:(1)Based on the research project of "Mountain Tunnel Waterproof and drainage Technology",which is under construction in Jiangxi Province,this paper aims at the adverse effects of tunnels on the environment for many years.Based on the study of waterproofing and drainage technology of mountain tunnel,it is pointed out that the trend of development is limited discharge,which is verified by tunnel disease cases and regulation analysis.(2)Based on the field investigation report and engineering survey of Gaowunshan Tunnel,the hydrogeological model of the tunnel is established,and the seepage force formula is deduced through the basic seepage theory and the analysis of the tunnel structure,combined with the external water pressure theory.The seepage force caused by underground water passing through lining is deduced and calculated,and the lining model is established by using ANSYS finite element numerical simulation software and the model parameters summed up by water injection test and relevant specifications.(3)Through the safety factor of lining,the thickness of lining and the thickness of grouting ring are optimized by stages,and the conservative design scheme of tunnel structure is put forward.On the basis of conservative design scheme of tunnel structure,the water shutoff parameters of limited discharge mode are added to adjust the effect of external water pressure on tunnel,and the water plugging standard of structure is calculated by lining safety factor.The influence of the water plugging structure on the bias voltage of the tunnel is investigated again,which provides theoretical support for the engineering practice.