Study On Surrounding Rock Pressure And Key Construction Technology Of Deep Buried Loess Tunnel With Different Water Content Zones

With the development of the economy in the west,high-speed railways have developed rapidly in the northwest of China,and a lot of loess tunnels have emerged,of which largesection loess tunnels have become the mainstream structural form.Since loess is a special kind of soil,the physical and mechanical properties of loess are significantly affected by the water content,which affects the surrounding rock load and structural deformation of loess tunnels.Loess tunnels are faced with the following problems: the distribution characteristics of confining pressure load of loess tunnels with different water content are not clear,and the deformation of surrounding rock is large.However,the calculation method,displacement control reference values and support parameters of surrounding rock pressure in loess tunnel are not considered in the current relevant standard.In view of this,this paper investigates the surrounding rock pressure,deformation characteristics and stability of deep buried loess tunnels with different water content by means of data investigation,field test,numerical calculation and theoretical analysis,and mainly achieves the following results:1.By means of field investigation and statistical analysis,the distribution of loess properties and the influence of water content on physical and mechanical parameters of loess are obtained.Based on 273 data samples,the fitting formulas between physical and mechanical parameters and water content are obtained.2.Using field test,theoretical calculation and numerical calculation,the calculation method of surrounding rock pressure and distribution mode of surrounding rock load of deep buried loess tunnels with different water content zones are obtained.3.Through field investigation,literature research and numerical simulation,the stability of deep buried loess tunnel is studied.Considering the influence of water content on the stability of deep buried loess tunnels with large section,the construction methods of different water content zones are explored,the displacement control reference values of different water content zones are given,and the construction parameters and support parameters of different water content zones are determined.The above results have been used in the construction of loess tunnels on Zhengxi Passenger Dedicated Line,Baolan Passenger Dedicated Line and Yinxi High-speed Railway,which can provide useful guidance for further improving the design and construction techniques of deep-buried loess tunnels.