圆孔扩张理论为桩基挤土位移预测和旁压试验结果分析等提供了理论依据,而现有解答中缺乏对土体结构影响的系统分析.基于考虑胶结作用的模型Cemented-CASM,推导了反映土体应力-应变关系的弹塑性刚度矩阵,在此基础上联立硬化法则和大应变理论,得到了不排水条件下结构性土中圆柱孔扩张问题的弹塑性解答.在不考虑土体结构性时,将退化解答与已有修正剑桥模型解答进行比较;在考虑结构性影响时,与旁压试验数值模拟结果比较,验证了解答的可靠性.通过参数分析说明了结构性及其退化对圆柱孔扩张过程的影响,结果表明:与重塑土相比,结构性土中扩孔引起的有效应力和孔隙水压力更大,而孔周塑性范围更小;随着结构的破坏,孔周土体表现出应变软化特征,径向应力随到孔壁距离的减小呈先增后减的变化趋势;土体结构完全破坏时,其有效应力与重塑土中趋于一致;土体结构性越强,相同扩孔压力或孔径变化下结构退化越快,软化特征越明显.

The cavity expansion theory provides a theoretical basis for the displacement prediction of the installed piles and the analysis of pressuremeter test results. However, there is a lack of systematic analysis of the influences of soil structure in the existing solutions. In this paper, based on the Cemented-CASM considering the cementation effect, an elastoplastic solution for the cylindrical cavity expansion under undrained condition was presented by deriving the elastic-plastic.pngfness matrix reflecting the soil stress-strain relationship in combination with the hardening laws and larger-strain theory. To verify the validation of the present solution, it was compared with the solution in Modified Cam Clay soils when ignoring the soil structure and compared with the numerical results of pressuremeter tests when the soil structure was considered. Parametric analyses were conducted to illustrate the effects of soil structure and destructuration on the cavity expansion process. The results show that the effective stresses and pore water pressure caused by the cavity expansion in structured soils are larger than those in reconstituted soils, while the plastic range around the cavity becomes smaller due to the soil structure. With the damage of the structure, the soil exhibits a strain softening behavior, while the radial stress increases and then decreases as the distance from the cavity wall decreases. When the soil structure is completely destroyed, the effective stresses around the cavity are consistent with those in the reconstituted soils. As the soil structure strengthens, destructuration become faster under the same variation in cavity expansion pressure or cavity radius, and the strain softening behavior becomes more pronounced.