Research on the Surface Deformation Prediction for Curved Shield Construction in Clay Stratum

Research purposes: The engineering problems, such as violent ground deformation, asymmetrical surface subsidence, are easily to be caused by small-radius curved shield construction, and the surface deformation law in small-radius curved shield construction has obviously variation with shield driving in straight line. In the engineering background of small-radius curved shield construction in thick alluvial clay strata in Jinan, the influence law of tunnel depth and radius of curvature on surface deformation was discussed. The surface deformation prediction formula for curved shield tunnel was established based on the Peck formula and field monitoring data. Research conclusions:(1) The phenomenon of differential disturbance on both sides of tunnel and asymmetrical surface deformation was caused by the influence of cutterhead overbreaking in shield turning part, shield shell pushing stratum by actively-hinged and uneven thrust of hydraulic jack. (2) The maximum surface settlement, width coefficient of settlement trough and ground loss ratio increase linearly with the increase of buried depth in the buried depth of 1.5~3 times tunnel diameter. The surface subsidence trough migration increases linearly with the decrease of radius of curvature. (3) The modified Peck formula fits well with the field monitoring data, and the range of correction coefficient is α=0.46~0.52, β=0.43~1.16. (4) The research results are of important guiding significance to the prediction of ground deformation and prevention and control of disaster for small radius curve shield tunnel in clay stratum. © 2018, Editorial Department of Journal of Railway Engineering Society. All right reserved.