Study On Reinforcement Technology Of Soft Ground For Jianshan Tunnel Of Zhongwei-Lanzhou Passenger Railway Line

The geological structure of the mountainous region of western China is complex and changeable.In the course of tunnel construction,there are many bad geological bodies such as soft rock,expansive rock and collapsible loess.Firstly,the support structure is greatly affected by force and deformation,and the collapse often accurs.On the other hand,the bearing capacity of the surrounding rock of the tunnel arch foot or the inverted arch is not enough,which causes the whole or partial large settlement of the tunnel,leading to the tunnel overall or partial large settlement,resulting in the tunnel.The failure of supporting structure is the problem of soft ground in tunnel.Soft foundation weakens the supporting condition of supporting structure,and the arching effect of surrounding rock is not easy to play,which seriously affects the safety and progress of construction.How to recognize and deal with the tunnel diseases caused by soft ground is an important topic for tunnel design and construction.In this paper,based on the Jianshan tunnel project of the control project of the Gansu section of the Middle School of China,the research method combined with various means,such as field geological survey,indoor geotechnical test,engineering analogy analysis and numerical simulation,is used to carry out the research of soft foundation reinforcement technology in tunnel,and the following research results are obtained.(1)By means of field geological survey,data collection and laboratory test,the types,causes,distribution characteristics and physical and mechanical parameters of the soft foundation in the tunnel entrance of Jianshan tunnel are explored to provide the basis for the rational formulation of the reinforcement measures.(2)The author summarizes the commonly used soft foundation reinforcement measures for tunnel engineering.According to the characteristics of the soft foundation of Jianshan tunnel,the common reinforcement measures are compared synthetically,and the soft foundation of collapsible loess is strengthened by the rotating spray in this paper.(3)Taking the shallow buried section of Jianshan tunnel entrance as the research object,the three-dimensional numerical analysis of tunnel construction stability is carried out by FLAC3 D.The distribution and change of stress field,displacement field,plastic zone and supporting structure of surrounding rock before and after the reinforcement of the tunnel basement are studied in detail,and the reinforcement effect of the reinforcement measures is evaluated and evaluated comprehensively.The research work provides reference and technical support for tunnel excavation and foundation treatment.