筋箍碎石桩复合地基桩土应力比的计算与分析

针对筋箍碎石桩复合地基的受力变形特点,考虑桩-土的初始应力状态,假定桩为具有恒定剪胀角的弹塑性体,且满足摩尔库伦屈服准则与非关联流动法则,土体和加筋体为线弹性材料,考虑桩-筋材-土三者间相互作用,导得了筋箍碎石桩复合地基桩土应力比计算新公式.为验证本文计算公式的可行性,将本文方法计算结果与弹塑性极限分析方法结果进行对比分析,两者吻合良好.在此基础上,分析探讨了筋材刚度、桩周土变形模量、面积置换率等因素对筋箍碎石桩复合地基桩土应力比的影响.分析结果表明:筋材刚度是桩土应力比的主要影响因素,桩土应力比随筋材刚度、面积置换率、桩体内摩擦角的增大而增大,随着桩周土变形模量和桩体剪胀角的增大而减小.

Study on Pile-soil Stress Ratio of Composite Foundation Reinforced with Geosynthetic Encased Stone Columns

Based on the deformation characteristics of the composite foundation reinforced with encased stone columns under vertical loads, a new calculation formula to estimate the pile-soil stress ratio of geosynthetic-encased stone columns was proposed with consideration of pile-geosynthetic-soil interactions. In the derivation process, initial stresses in soil and a column were taken into account, the column was considered as an elastic-plastic material with constant dilatancy angle and satisfying both the Mohr-Coulomb yield criterion and non-associated flow rule, and the soil and geosynthetic encasement were considered as linear-elastic materials. The proposed formula was validated by comparison with the results of elasto-plastic limit analysis method. Finally, a parametric study was conducted to investigate various parameter effects of encasement stiffness, deformation modulus of soil, and replacement ratio on the behavior of the pile-soil stress ratio. The parametric study shows that the pile-soil stress ratio of the composite foundation with the encased stone column increases with the increase of encasement stiffness, replacement ratio of composite foundation and friction angle of the column, but decreases with the increase of deformation modulus of soil and dilation angle of column. Moreover, among all these parameters, the encasement stiffness hasd a significant influence on the pile-soil stress ratio.