Study On High-speed Railway Tunnel Foundation Reinforcement Technology And Response To Train Vibration In Diatomite Stratum

Diatomite is a kind of special soil with strong structure,unique mineral composition and physical and mechanical properties.At present,the research results and design and construction experience of high-speed railway tunnel crossing diatomite soil layer are lack.Based on the Feifengshan tunnel project of Hangzhou-Shaoxing-Taizhou high-speed railway,this paper studies the foundation reinforcement echnology and train vibration response of high-speed railway tunnel in diatomite soil layer by theoretical analysis,field comparison test,and field inverted arch stress monitoring and dynamic numerical analysis.The main research contents and conclusions are as follows:(1)The pile forming effect and bearing capacity tests of reinforcing diatomite foundation by high pressure jet grouting pile and steel pipe pile were carried out respectively.After comprehensive comparison,the steel pipe pile is selected as the reinforcement technology of the foundation,and the design parameters and construction scheme are determined.Through the field monitoring results,the contact pressure between the steel ribs and the surrounding rock,the stress of the primary support and the shotcrete,the primary support bending moment and the axial force VS time are analyzed,which verifies that the force of the invert force is in a reasonable range after reinforcing by steel pipe pile.(2)Based on the vehicle-rail coupling dynamic model method,the dynamic calculation model of diatomite high-speed railway tunnel is established,the dynamic response law of the diatomite tunnel is studied in different influence factors,the results are as follows: 1)The reinforcement measures should be taken in time before the surrounding rock deterioration of the tunnel.2)The better the surrounding rock quality of diatomite is,the smaller the acceleration and displacement responses of tunnel structure is.3)The acceleration response of the lining is nothing to do with the depth of the tunnel,regardless of the steel pipe piles or not,and the displacement response of the lining decreases gradually with the depth of the tunnel increases,and the control effect of steel pipe pile on dynamic displacement becomes more obvious with the increase of the depth of the tunnel.4)With the increase of the train speed,the dynamic response of the tunnel structure increases,and the increase rate becomes larger,but the reinforcement effect of steel pipe piles becomes more limited.5)The larger the pile length and diameter is,the smaller the dynamic response of tunnel structure will be,but the influence of pile length and diameter on the dynamic response of tunnel structure will be smaller with the pile length and diameter increases.6)Steel pipe pile reinforcement can optimize the acceleration response of the tunnel structure and effectively reduce the displacement response of tunnel structure.(3)Based on the improved cumulative settlement prediction model,the long-term cumulative deformation of the basement of diatomite high-speed tunnel under the different influence factors is analyzed,and the main results are as follows: 1)Basement reinforcement measures should be taken in layered place of the surrounding rock in advance,which is good for the long-term cumulative settlement.2)The better the surrounding rock quality of diatomite is,the smaller the long-term cumulative settlement and dynamic response of the surrounding rock is.3)The larger the depeth of the tunnel is,the smaller the long-term cumulative settlement and dynamic response of the surrounding rock is,and the decrease rate decreases with the depeth of the tunnel increases.4)With the increase of the train speed,the dynamic response of the surrounding rock and the long-term cumulative settlement increases,and the increase rate increases with the train speed increases,the reinforcement effect of steel pipe piles becomes more limited.5)The larger the pile length and diameter is,the smaller the dynamic response of the surrounding rock and the long-term cumulative settlement becomes,but the influence of pile length and diameter on the dynamic response of tunnel structure will be smaller with the pile length and diameter increases.6)Steel pipe pile reinforcement can obviously reduce the long-term cumulative settlement of the tunnel basement and the settlement increase rate during operation.