Analysis Of Influence Of Grouting Ring On Load And Internal Force Of Composite Lining In High Pressure And Water Rich Tunnels

With the rapid development of China’s transportation construction,mountain tunnel construction is increasing day by day,inevitably through the high water pressure and rich water area.In practical engineering,grouting and composite lining with waterproof and drainage system are often used to ensure the safe construction and operation of high-pressure water rich tunnel.At present,the selection of grouting parameters and allowable displacement of drainage system in construction is only based on experience,and there is a lack of systematic research on the influence of different parameters on lining stress.If the parameters are not properly selected,it will not only increase the construction cost and delay the construction period,but also endanger the safety of tunnel driving.Therefore,it is of great engineering significance to study the influence of grouting on the load and internal force of composite lining under different drainage limits.Based on this,relying on the zhengpantai tunnel of Chongli railway,this paper studies the influence of grouting on lining stress under different waterproof and drainage conditions through theoretical and numerical analysis methods on the basis of literature research,and puts forward the selection basis of reasonable grouting parameters and section optimization method.The main work and research results are as follows:(1)Theoretical analysis method is used to analyze the external water pressure of lining and the lining stress and displacement considering seepage under different displacement,and the analytical formula of tunnel water pressure,lining stress and displacement is obtained,which provides theoretical guidance for the calculation of water pressure and stress characteristics of high-pressure water rich composite lining tunnel.(2)Based on the existing Yuanliangshan Tunnel,a numerical model of tunnel is established to study the external water pressure on the lining under seepage.The accuracy of the numerical model and parameter selection is verified by theoretical analysis and existing model tests.In addition,the numerical simulation and theoretical analysis methods are used to analyze the lining stress and deformation of the new Zhengpantai Tunnel under different working conditions,and the applicability of the numerical model to Zhengpantai Tunnel is verified.(3)Based on the numerical model,the influence of grouting area and parameters on the external water pressure and internal force of lining under different limited displacement conditions is studied.It is concluded that the water blocking effect of grouting in high-pressure water rich tunnel is obviously greater than that of stratum reinforcement;The drainage system can discharge and dredge the groundwater;If the engineering conditions permit,the combination of water plugging and drainage restriction,grouting and composite lining with waterproof and drainage layer should be adopted to ensure the safe construction and operation of the tunnel.(4)Based on the numerical model,the influence of grouting area and parameters on the external water pressure and internal force at different parts of lining is studied.It is concluded that increasing the thickness of grouting ring and reducing the permeability coefficient have the best reduction effect on the stress of lining,and the maximum reduction effect on the internal force of tunnel lining can reach 40%-60%,but the reduction effect tends to be gentle when it increases to a certain extent;The stress of the lining is different at different positions,and the most unfavorable position of the lining is at the foot of the wall;The effect of grouting on the stress reduction of lining is different at different positions.The best position of grouting on the internal force reduction of lining is at the invert.(5)On the basis of the above research results,the method of drawing safety curve is proposed to select reasonable grouting parameters,and the optimization methods of local thickening grouting circle and increasing the rise span ratio of lining invert are proposed to provide the optimization scheme when the safety of local lining of high pressure and rich water tunnel is insufficient.