Safety Analysis And Monitoring And Early Warning Of Deep Buried Highway Tunnel Under High Water Pressure Condition

In recent years,along with General Secretary Xi Jinping's proposal of the “One Belt and One Road” major strategy,the northwestern provinces of the inland regions(Ningxia,Qinghai,and Gansu and Shaanxi),the western provinces(Chongqing,Sichuan,and Yunnan)and the central provinces(Henan)were among the others.The western provinces will surely become the transportation hub connecting the Asian and European countries and the inland cities of the country,and assume greater responsibility for the interconnection of the transportation.However,the transportation construction in the western mountainous areas is faced with a variety of complex environmental constraints.For example,under the condition of high water pressure,the construction and operation of deep-buried highways will face great challenges.During the construction of this kind of water-rich karst tunnel,frequent geological disasters such as karst rivers,water inrush and mud outbursts are frequently encountered.Because of the abruptness of water inrush and mud,construction workers are often too late to take response measures.The loss is also difficult to estimate,so we need to pay special attention to it.On the basis of the combination of relying on the project construction practice,this article combines the actual investigation of the scene and the indoor comprehensive analysis to carry out relevant research work,and the main results obtained are as follows:(1)Analyze the geological conditions,hydrology and karst section characteristics of the project site.Four kinds of methods were used to predict the inrush water volume of the project.Then,based on the characteristics of “mainly blocking and limited discharge” adopted by the project,a preliminary estimate of the external water pressure of the lining is made using a suitable external hydraulic pressure reduction factor.(2)Inquire into the basic theory of groundwater seepage through the hypothesis of axisymmetric symmetry.It is proved that the equivalent continuum theory is also applicable to the seepage problem of massive fractured rock mass.Using analytical solutions,the computational model is degenerated into axisymmetric problems and the principle of conformal change is used to analyze deep-buried karst tunnels under high water pressure conditions.It is concluded that for composite linings,the effect of the seepage force on the lining can be reduced to the effect of the radial surface force of the pore water pressure on the lining,and the complex “continuous” model can be replaced by a simple “load-structure” model.The volume calculation model" then performs finite element calculations on the lining structure.(3)Ansys finite element software was used to simulate numerically the structural stress of the SK3 type hydraulic pressure resistant lining used in the Spring Gate Tunnel under five different partial pressure conditions.The analysis was performed under different conditions.The axial force and bending moment of the lining are obtained,and the weak links of the second lining under corresponding working conditions are obtained.(4)Three different thicknesses of hydraulic pressure resistant linings used for the second lining of the Chunmen tunnel are simulated using Ansys finite element software to simulate their stress in five different pressure modes,and three types of water pressure resistance are analyzed.Lining safety factor under different pressure conditions.(5)The function and composition of the long-term monitoring and warning system for tunnel linings are described.The water pressure monitoring data for specific projects are analyzed and early-warned using the results of finite element software simulation.Finally,the pressure relief value of the automatic pressure relief system outside the lining is optimized.