碎石桩法在软基处理中应用广泛,目前对该型复合地基抗剪特性定量研究较少,不能很好支撑实际工程需求。以物理模型试验和数值试验为主要手段,研究了碎石桩复合地基抗剪机制,得到以下结论:①以实际的碎石桩置换率19.6%为参照,对复合地基分别开展了无包裹常规碎石桩和透水橡皮膜包裹碎石桩的不固结剪切,以及无包裹碎石桩固结剪切单剪物理模型试验。3种方案复合地基反馈的抗剪能力较天然软基均提升显著,但前2种方案抗剪强度参数差异不大,而固结剪切方案较前两者有更进一步提升,表明桩周软土对散体状碎石桩的柔性约束能使其呈现整体均匀式剪切特征,碎石桩对软基渗透性能的显著改善是复合地基抗剪强化的关键。②将碎石桩置换率由19.6%提升至24.5%开展一组不固结剪切对比试验,与置换率19.6%的固结剪切状态相比,两者强度差异不大,表明在较低置换率区间,从发挥该类型复合地基抗剪强度的角度来看,促进地基固结更为经济有效。③以不同排水固结状态桩间土抗剪强度参数为主控因素,开展复合地基剪切数值模型试验,分析认为物理模型试验中桩间土反馈的抗剪强度较相应排水固结路径均有所提高,验证了碎石桩能显著改善软基渗透性的判断,进一步分析揭示了复合地基剪切变形及剪应力传递规律。

Stone columns are commonly used in the treatment of soft foundations. However, there is a lack of quantitative research focused on their shear strength characteristics, which limits their ability to meet actual engineering needs. This study investigates the shear strength characteristics of stone column composite foundations using physical model tests and numerical experiments as the main technical methods. The following conclusions were drawn: 1) Three groups of simple shear model tests were conducted with a stone column replacement rate of 19.6% under unconsolidated, unconsolidated with flexible permeable membrane wrapped stone columns, and consolidated conditions respectively. Compared with the original soft foundation, the shear strengths of the composite foundations were significantly improved. The first two schemes showed very similar shear strength, while the consolidated scheme exhibited further improvement. This suggests that the flexible constraint of soft soil around the stone columns can enhance the overall shear characteristics of the composite foundation. The shear strength of the composite foundation was closely related to the significant improvement of permeability performance. 2) Another group of unconsolidated shear tests was conducted after increasing the replacement rate of stone columns from 19.6% to 24.5%. Compared with the consolidated shear test under a 19.6% replacement rate, the difference in shear strength was not significant. This indicates that promoting consolidation can be a more economical and effective way of improving the shear strength of the composite foundation at relatively low replacement rates. 3) Numerical shear tests of stone column composite foundations were carried out. The shear strength parameters of soil in different consolidation and drainage states were selected as the main control factor. Compared with the shear strength parameters of soil in the corresponding consolidated and drainage states, the feedback shear strength parameters of soil around columns in physical simple shear tests were improved. This verifies that stone columns significantly improve the consolidated and drainage environment of natural foundations. Overall, this study provides valuable insights into the shear strength characteristics of stone column composite foundations and proposes effective methods of improving their performance in practical applications.