Mechanism of three dimensional elastic-plastic expansion of cylindrical cavity in saturated clay
LI Jingpei1，2，TANG Jianhua1，2，LI Lin1，2，ZHONG Guangyu3
(1. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China；2. Department of Geotechnical Engineering，Tongji University， Shanghai 200092，China；3. Shanghai Nanhui Construction Group Co.，Ltd.，Shanghai 201399，China)
Abstract：The current solutions of cylindrical cavity expansion are based on an elastic-perfect plastic assumption. The consistency in shear deformation and shear failure is not warranted and the over-consolidation ratio and three-dimensional strength characteristic of soil also are not incorporated into the solutions. Therefore，a large deviation between the theoretical solutions and the actual conditions exists. To obtain the exact solution of elasto-plastic expansion of cylindrical cavity，the SMP criterion revised by Cam-Clay model was adopted using the associated flow rule in the stress transformed space，which can incorporate the over consolidation ratio and the soil strength in three-dimensional stresses state. The problem was reduced to a system of first order ordinary differential equations in the plastic region using the large strain deformation theory. The accurate solution to cylindrical cavity expansion was obtained by means of a numerical method under the elastic-plastic boundary conditions. Finally，the stress around the cavity during the cavity expansion process was discussed by comparing with the solutions based on the MCC model. The results showed that the solutions with SMP-MCC model reflected the change of stress field more actually，because the three-dimensional strength of soil was considered in the present solution.