中文摘要：

为研究天然饱和黏土中圆孔不排水扩张引起的土体力学响应,考虑天然饱和黏土的K_0固结特性、应力历史及柱孔扩张过程中径向、环向和竖向应力之间的关系,基于修正剑桥模型和大变形理论,结合弹塑性边界条件推导了K_0固结饱和天然黏土中柱孔不排水扩张问题的弹塑性解析解,并与既有数值解答进行对比验证.在此基础上,通过与以往基于初始应力各向同性假设下的柱孔扩张解答进行对比分析,研究了土体K_0固结特性和应力历史对柱孔扩张过程中土体应力和塑性区半径的影响.研究结果表明：本文提出的柱孔扩张弹塑性解答与既有基于严格本构关系的数值解基本一致,且可以退化为基于初始应力各向同性假设条件下的解答;土体K_0固结特性和应力历史对柱孔扩张过程中周围土体应力场和塑性区半径存在一定程度的影响,特别对极限扩张压力的影响较为明显,且其影响程度均随初始各向异性的增加而增大.研究结果为天然饱和黏土地基静压沉桩、旁压试验提供了一定的理论依据.

英文摘要：

To study the mechanical responses induced by undrained expansion of a cavity in natural clay soils, considering the K0-consolidated property and the stress history of the natural saturated clay, as well as the relationship among the radial, tangential, and vertical stresses, an elasto-plastic analytical solution to the undrained cylindrical cavity expansion in K0-consolidated saturated natural clay, which was under the initial stress anisotropic condition, was derived based on the modified Cam-clay （MCC） model, large-deformation theory and the elastic-plastic boundary conditions.The solution presented in this paper was verified by the well-documented numerical solution and compared with the previous initial stress isotropy assumption based solution.The effect of the K0-consolidated property and stress history on the stress fields and the plastic radius during the cavity expansion process was discussed in detail.The results show that the present closed-form elasto-plastic solution matches the numerical solution fairly well, and the present solution can be reduced to the initial stress isotropy assumption based solution.The K0-consolidated property has a significant effect on the stress fields around the cavity during the cavity expansion process, especially on the limit cavity expansion pressure.The effect of the initial stress anisotropy on cavity expansion increases with the degree of the initial stress anisotropy.This paper provides a theoretical benchmark for pile installation and pressuremeter test in natural clay soils.