Disposal Technology Research And Numerical Simulation Analysis On Subgrade Water Inrush Of Highway Tun Nel In Karst Area

The rapid growth of China's economy,the western region where railways and transportation networks are backward has become the focus of China's infrastructure construction.There is a large area of collapsible loess area in western China.In the process of road and railway network construction,shallow-buried loess tunnels are inevitable,and the characteristics and construction methods of loess due to its speciality are quite different from those of ordinary tunnels..Therefore,in order to ensure the safety and economy of shallow tunnels in the loess area,it is necessary and urgent to study the mechanical characteristics and construction control measures of shallow tunnels in the loess area.In this paper,the judgment basis of existing deep-buried tunnels is studied in detail,and the common failure models,deformation and stress characteristics of shallow tunnels are summarized.The finite element is used to further understand the mechanical characteristics of shallow tunnels in loess area and the optimal conditions.Construction plan,specifically:(1)A large number of literatures were reviewed,and the demarcation methods and applicable scopes of existing shallow and deep buried tunnels were well known.It is concluded that the normative method and the boundary between deep and shallow tunnels deduced by Xie Jiaxuan are more suitable for tunnels in the loess area;(2)According to the shortcomings of shallow tunnel embedding to surr ounding environment and unsuitable for arching,the common failure modes and surrounding rock pressure calculation theory of shallow tunnels in loess area are analyzed,and the instability of surrounding rock of shallow tunnel in loess area is summarized.Failure mechanism(3)Taking the shallow buried tunnel in a loess area as an example,the construction organization design and on-site monitoring measurement method are introduced in detail.This method is used to safely and effectively complete the excavation of shallow tunnel in the loess area,and the loess area is obtained.More effective safety excavation methods and support techniques for shallow tunnels;(4)The tunnel excavation model is established by numerical simulation method for different thicknesses and different excavation methods.The deformation of the arch of the surrounding rock of the shallow tunnel in the loess area is large.During the excavation process,it should be noted that it can be opened when necessary.Pre-reinforcement before excavation;when the tunnel depth is large,pay attention to the uplift failure of the tunnel inverting arch;when the tunnel is shallowly buried,it is better to use the three-step method to excavate.When the tunnel is in the deep and shallow depth range,the two-step method is appropriate.