基于广义SMP准则及应力路径法的柱孔扩张分析

柱孔扩张理论广泛用于旁压试验机制分析、沉桩挤土效应等岩土工程问题中。基于经典的Vesic孔扩张理论，采用能够考虑中主应力效应的广义SMP屈服准则，并结合有限应变理论对均质土体中柱孔扩张问题进行分析，根据应力路径假设提出确定塑性区平均体应变的解析步骤。通过大量变参数计算给出具有不同刚度指标 、泊松比 和内摩擦角 的土中柱孔扩张极限状态下的塑性区平均体应变、孔扩张半径比和孔扩张系数。分析结果表明， 、 、 越大，塑性区平均体应变越小，塑性区半径比越大，孔扩张系数越大；随着 增加， 的变化对孔扩张系数的影响更显著。同时，将结果与基于Mohr-Coulomb准则的孔扩张解答进行比较，探讨不同土性参数时中主应力效应对孔扩张系数的影响。文中分析方法及给出的考虑中主应力效应的柱孔扩张系数表可为原位试验分析及桩侧摩阻力估算提供参考。

Analysis of cylindrical cavity expansion based on extended SMP criterion and stress path approach

The theory of cylindrical cavity expansion has been widely used in many geotechnical engineering, such as analysis of pressure meter testing and effect of pile driving. Extended spatial mobilization plane (SMP) theory, which can display the effects of intermediate principal stress, in combination of finite strain theory, is used to analyze cylindrical cavity expansion problem in homogeneous soil. An analytical procedure to determine average volumetric strain of plastic zone is developed according to stress path hypothesis. Accordingly, “nondimensional” plastic zone radius and factors of cylindrical cavity expansion are estimated for varied rigidity index , Poisson ratio v and frictional angle . It is concluded that average volumetric strain decreases and “nondimensional” plastic zone radius and factors of cylindrical cavity expansion increase with the increase of 、 、 . Variation of has significant effects on factors of cylindrical cavity expansion in the case of greater . Furthermore, a comparative study of the solutions based on extended SMP and those based on Mohr-Coulomb is made to examine the effects of intermediate principal stress on cylindrical cavity expansion for various soils. The values of factors of cylindrical cavity expansion considering the effects of intermediate principal stress presented in this paper are of great significance for analyzing in-situ tests and estimating ultimate lateral friction of piles.