Study On The Influence Of Drainage Mode On The Deformation Of Inverted Arch Of High Speed Railway Tunnels

Due to the vast territory and complex geological conditions in China,various diseases occur frequently in the construction and operation stage of railway mountain tunnels in China,and diseases of the inverted arch structure are particularly prominent in railway tunnels.At present,the main consideration for the deformation of inverted arch generated by groundwater is the effect of water on the surrounding rock,the surrounding rock will become weak after contact with water and cause damage.And because of the fluidity of the water and the transferability of water pressure,the lining structure of the tunnel is often subjected to higher water pressure.There is little research on the deformation of the inverted arch under water pressure.Understanding the reasons for the uplifting of the inverted arch under water pressure and how to select a reasonable drainage pattern are crucial for reducing the influence of groundwater pressure on the deformation of the inverted arch.the influence of the outbreak of the tunnel lining under external water on the cause of deformation.This paper relies on the proposed tunnel construction of the Chengkang section of the Sichuan-Tibet Railway.Theoretical analysis,numerical simulation and model test methods are used to study the influence of the outbreak of the tunnel lining under external water on the cause of deformation and the effect of different drainage modes on the deformation of the inverted arch of the tunnel.The main research results are as follows:Tunnels that were deformed due to water pressure were analyzed.Three causes of deformation of the inverted arch under water pressure have been summarized.Comparing and analyzing the commonly used tunnel drainage patterns.Their advantages and disadvantages have been summed up,especially for the impact of inverted arches in water-rich formations.Based on the related percolation theory,this paper describes the principle and process of finite-difference software FLAC3 D for fluid-structure interaction simulation.Through the numerical simulation method and the model test,the effects of the permeability coefficient of the surrounding rock,water head height,and the gap between the primary support and the secondary lining on the uplift of the invert arch under water are analyzed.And it is found that if there is a gap between the primary support and the secondary lining,the effect of water pressure on the deformation of the inverted arch is greater than the head height and the surrounding rock coefficient.The presence of the drainage system has a great influence on the water pressure of the lining structure.Through the numerical simulation method and the model test,the two drainage modes of both side drainage and inverted arch drainage are analyzed.It is found that in the case of a good drainage,the presence of the drainage system can better reduce the lining water pressure and relieve the deformation of the inverted arch.Because the water pressure at the bottom of the tunnel is higher than the arch feet,drainage of the inverted arch can improve the stress conditions of the invert arch compared to setting the drain holes at the arch feet.Lining internal forces will increase as the head height increases.Under the effect of water pressure,the existence of the gap between the second liner and the initial branch has little effect on the internal force of the liner.At the same time,under the drainage system drainage,the water pressure of the cross-section lining of the annular drain pipe and the drain hole is smaller than that of other sections,and the lining stress is greater than that of other sections.Drainage on both sides can reduce the internal forces of the lining other than the arch feet,but the internal force at the arch foot will increase.The drainage system can reduce the water pressure of the lining and increase its safety factor.The drainage system can reduce the water pressure of the lining and increase its safety factor.