Research On Installation Of Safety Protection Area For Shallow-buried High-speed Railway Tunnel

The operation practice of Zhengxi High-speed Railway shows that during the operation of shallow-buried high-speed railway loess tunnel,the construction operation above the tunnel(filling and excavating,building structures,etc.)has certain influence on the structure,building boundary and track variation of shallow-buried high-speed railway tunnel.The boundary between buried and shallow-buried loess tunnel is obviously different from that of stone tunnel and general soil tunnel,and its influence can not be ignored.Therefore,safety protection zones should be set up for shallow high-speed railway loess tunnels.In this paper,the deep-shallow burial boundary of loess tunnel is studied firstly,and the deep-shallow burial boundary depth of large cross-section loess tunnel is determined by theoretical calculation combined with the actual situation of many tunnels of Zhengzhou-West High-speed Railway.Based on Gongyi Tunnel of Zhengxi High-speed Railway,combined with the actual disease situation,the influence of surcharge and unloading caused by surface filling and excavation on the tunnel under different burial depth is analyzed.The V-G model is also used to fit the unsaturated seepage characteristics of collapsible loess in the surface layer,and the seepage depth of rainwater during surface rainfall is determined.On this basis,the influence of surface surcharge on shallow tunnel is further analyzed.Finally,the above calculation results are used to delimit the safety protection zones of shallow high-speed railway tunnel in loess stratum combined with the existing standards for the establishment of subway safety protection zones,and the corresponding measures and suggestions are put forward.