中文摘要：

混凝土芯砂石桩能够有效地减少工后沉降和工后差异沉降。为进一步了解混凝土芯砂石桩复合地基的加固机理,预制芯桩对复合地基承载力的提高作用以及砂石壳加速固结排水的作用,采用基于ABAQUS有限元数值分析方法建立轴对称平面应变模型,对混凝土芯砂石桩单桩及单桩复合地基载荷试验进行模拟,并将结果与现场实测数据进行对比。对单桩沉桩过程进行了模拟,并结合圆孔扩张理论和砂井固结理论进行分析。研究结果表明：预制芯桩承担了大部分上部附加荷载,最终荷载分担比约为0.7,有助于提高复合地基承载力;沉桩至5m深度处,地基土隆起对沉桩引起的超孔压影响不大,砂石桩的存在大大加快了地基土中超孔隙水压力的消散和桩周土强度的恢复。

英文摘要：

The concrete-cored sand-gravel columns can effectively reduce post-construction settlements and differential post-construction settlements.For a further study of the reinforcement mechanisms of the composite foundation improved by concrete-core sand-gravel columns,which includes the effects of the inner pile on improving the bearing capacity of the composited foundation and the influence of the sand-gravel shell on accelerating the consolidation rate of the subsoil,the axisymmetric plane-strain models were established based on the numerical software ABAQUS to simulate the single column loading test and single column composite foundation loading test,the results of which were compared with the field monitoring results.The single column sinking process was simulated and analyzed in combination with the cavity expansion theory and sand-well consolidation theory.The research results show that the inner pile takesmost of the overloads with a final load sharing ratio of 0.7,which contributes to improving the bearing capacity of the composite foundation.The soil heave does not affect the excess pore pressures caused by column sinking at 5mdepth,and the existence of the sand-gravel shell accelerates the dissipation of the excess pore pressures and the strength recovery of the surrounding subsoil.