为揭示褥垫层颗粒材料的力学本质，深入研究其对刚性桩复合地基性能的影响，开发了有限差分－颗粒流(FDM- PFM)耦合方法，建立了刚性桩复合地基静载试验耦合模型;将耦合模型计算结果与某高层建筑结构现场静载试验结果进行了对比，吻合良好，证明该耦合方法有效，材料宏观、细观参数取值正确．并进一步模拟分析了不同褥垫层材料对刚性桩复合地基性能的影响，结果表明:随褥垫层刚度增大，沉降减小，桩土应力比增大，桩顶对褥垫层刺入量减小;不同褥垫层材料桩顶负摩阻区范围为中粗砂 0．30 L、碎石0．25L、级配砂石 0．20L(L 为桩长);随褥垫层刚度增大，负摩阻力减小，桩身轴力则增大．

In order to reveal the mechanical nature of granular cushion and deeply investigate the effect of granularcushion on the performance of rigid- pile composite foundation,a finite differential- particle flow (FDM- PFM) cou-pling method is proposed,and a coupling model for the static loading test of a single rigid- pile composite foundationis set up.Then,the calculation results are compared with the in- situ test results of a composite foundation of ahigh- rise building,with good accordance being found,which means that the proposed coupling method is effective,and that the macro and micro parameters are properly selected.Finally,further simulations are performed to ana-lyze the effects of different cushion materials on the properties of rigid- pile composite foundation.The results showthat (1) with the increase of cushion stiffness,the settlement decreases,the pile- to- soil stress ratio increases,andthe penetration of the pile top into the cushion decreases; (2) the range of negative skin friction area of the pile isdetermined as follows: 0.30L of medium and coarse sand,0.25L of crushed stone,and 0.20L of graded sand andstone; and (3) with the increase of cushion stiffness,the negative skin friction decreases,while the axial force ofthe pile increases.