Research On Monitoring And Measuring Early Warning Value Of Large Section Tunnel Displacement

With the rapid development of national economy,city construction speed is faster and faster,the city rail transportation,most of the station of large section tunnel engineering,construction and construction of large section tunnel compared with the conventional size of tunnel and puts forward new requirements on the mechanical behavior of tunnel sections,lining structure and construction method.The characteristics of tunnel displacement and deformation are related to geological conditions,design parameters,construction and management and so on,and the degree of influence is different.The traditional displacement early warning standard can not meet the construction requirements of the large section tunnel.Therefore,based on the Chongqing rail link large section Tu-shan station project,through strength reduction method,studied in different span,different embedding and different construction methods,the change rule of tunnel crown settlement and convergence around the warning value,obtained the following conclusions:(1)The control values of tunnel crown settlement and peripheral convergence increase with the decrease of safety factor,and increase with the increase of buried depth,and increase with the increase of span.(2)When the depth is 29 m,with the increase of the span,the control value of the vault subsidence increases from 34% to 73% of the current standard,and the control value of the circumference is increased from 45% to 96% of the current standard.When the span is 21.56 m,with the increase of the buried depth,the control value of the vault subsidence increases from 36% to 76% of the current standard,and the convergence control value increased from 50% to 90% of the current standard control value.(3)When the surrounding rock grade is I~ IV2,with the increase of the depth and span of the tunnel,the control value of the vault subsidence is increased from 33% to 72% of the current standard control value,and the surrounding convergence control value increases from 45% to 94% of the current standard control value.When the surrounding rock grade is grade IV3~ V1,with the increase of the depth and span of the tunnel,the control value of the vault subsidence is increased from 34% to 73% of the current standard control value,and the peripheral convergence control value increased from 48% to 96% of the current standard control value.(4)When the grade of surrounding rock is grade IV 1,the control value of the vault subsidence is 50% and the control value of the circumjacent convergence is 70% of the current standard control value when adopting the double side wall guide method.When the CD method is adopted,the control value of the vault subsidence is 60% of the current standard control value and the surrounding convergence control value is 54% of the current standard control value.When using the CRD method,the vault settlement control value is 54% of the current standard control value,and the peripheral convergence control value is 40% of the current standard control value.