NUMERICAL SIMULATION ON TIME-SPACE EFFECTS OF PLANE FROZEN SOIL WALL RETAINING DEEP-FOUNDATION PIT
平面冻土墙围护深基坑的时空效应数值模拟

Aiming at the existing problem of structural calculation in deep foundation pit supported by plane frozen soil wall,the numerical simulation of 3D FEM is presented. In the calculating model,it is considered that the frozen soil wall is made up of non-homogeneous visco-elasto-plastic media which follows the Mises yield criterion,and the ambient soil is elastic-plastic medium which obeys the Drucker-Prager yield criterion. At the same time,the interaction between plane frozen soil wall and ambient soil and the effect of step-by-step excavation are considered. Taking the deep foundation pit of original experimental segment in Nanjing subway as the prototype,the numerical simulation of time-space effect of plane frozen soil wall is performed by 3D FEM. The distribution rules are obtained of displacement and stress in the plane frozen soil wall and ambient soil during and after the excavation. The calculating results provide basis for design of deep-foundation pit supported by plane frozen soil wall,and indicate that creep property of frozen soil wall should be paid much attention to in actual engineering application. To optimize design parameter of plane frozen soil wall better,the calculating model is set up according to orthogonal design graph. By changing the thickness of frozen wall,freezing brine temperature and span of pit,their effects on stability of deep foundation pit are analyzed,and the regression equations of maximum horizontal displacements of frozen soil wall and settlement of ambient soil are obtained. Finally,a test model is analyzed and calculated by this procedure,and the calculation results are in good agreement with the test values. So it shows that it is reasonable and creditable to analyze the time-space effects of plane frozen soil wall by 3D FEM.