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目前饱和黏土中柱孔弹塑性扩张问题解答均假定土体为理想弹塑性材料,因而柱孔扩张过程中土体剪切变形和剪切破坏的一致性无法体现,且既有研究成果无法综合考虑超固结比及土体的三维强度特性,使得理论计算值与实际存在较大偏差。为得出饱和黏土中柱孔不排水扩张问题的精确解答,采用基于SMP准则改进的修正剑桥模型(SMP-MCC),充分考虑土体三维强度特性和超固结比,在转换应力空间使用相关联流动法则,进而将柱孔扩张问题归结为一阶偏微分方程组的求解问题。在此基础上,根据弹塑性边界处的应力和位移条件,采用应力转换方法在转换应力空间建立偏微分方程组的定解条件,并通过数值方法得到柱孔扩张问题的精确解答,通过与修正剑桥模型解答相对比,研究柱孔扩张过程中孔壁周围土体应力的变化规律。结果表明,由于提出的三维弹塑性精确解答充分考虑了土体的三维强度特性,因而可以更加真实地反应柱孔扩张过程中土体应力场的变化规律。
So far, the elastic-plastic expansions of column holes in saturated clay are all assumed to be ideal elastoplastic materials. Therefore, the consistency of shear deformation and shear failure in the process of column hole expansion can not be reflected, and the existing research results can not be considered synthetically Overconsolidation ratio and soil three-dimensional strength characteristics, making the theoretical calculations and the actual existence of large deviations. In order to get an accurate solution to the problem of undrained expansion in saturated clay, a modified modified Cambridge model (SMP-MCC) based on SMP criterion was adopted to fully consider the three-dimensional strength characteristics and overconsolidation ratio of soil, In addition, the problem of dilation of column holes is reduced to the solution of first-order partial differential equations. On this basis, according to the stress and displacement conditions at the elastic-plastic boundary, the solution conditions of the partial differential equations in the transformation stress space are established by using the stress transformation method. The exact solution to the problem of column hole expansion is obtained by numerical method. Cambridge model to answer the contrast, study the column hole expansion process of soil around the hole wall stress changes. The results show that due to the proposed three-dimensional elastic-plastic exact solution, the three-dimensional strength characteristics of soils are taken into full consideration. Therefore, the changing laws of stress field can be more realistically reflected.