Research On Soil Dynamic Characteristics And Settlement Under The Condition Of Shield Tunnel Construction And Operation

The long-term settlement due to subway from total time can be divided into two stages, which are the pre-settlement and settlement during subway operation. The settlement before subway operation is mainly caused by shield tunnel boring, which includes immediate settlement by soil loss, positive additive thrust, friction and after construction consolidation settlement from dissipation of excess pore water pressure and other reasons. The settlement during subway operation consists of soil accumulated plastic deformation and accumulated excess pore pressure dissipation by subway loads, which is also affected by shield tunnel construction.Based on shield tunnel engineering in Hangzhou and considering construction impacts caused by subway operation, the foundation soil dynamic properties and settlement were studied. The research contents and innovation include as follows.(1) Simplify the subway train moving load into multiple mobile axle loads. The characteristics of dynamic stress, changes of stress path load and main stress rotation were researched by single axle loads and train moving loads. Based on this theory, changes of soil element stress state of different shield tunnel depth right below the load line.(2) Based on former theory, the distribution of the excess pore water pressure was obtained by calculating when shield tunnel construction is completed. By use of MIDAS-GTS three-dimensional finite element model, the shield construction surface settlement and excess pore pressure distribution law were calculated at different period.(3) Based on Hangzhou Metro Line-1and considering the interaction between the subway car-body, wheels, track system, the kinematic coupling model of carriage, bogie and wheel were established. The load travel-time curve was added into the three-dimensional finite element model, and then the dynamic characteristics of foundation soil in different initial consolidation due to train operation were obtained. (4) The three locations excess pore water pressure changes law in tunnel vaults, tunnels bagging line and tunnel arch were researched caused by train moving loads when the degree of subsoil initial consolidation reaches100%,90%,70%separately.(5) The long-term after construction settlement consists of soil accumulated plastic deformation and accumulated excess pore pressure dissipation, and then long-term settlement at different initial consolidation due to Hangzhou Metro train operation were predicted.