高速铁路CFG桩-筏复合地基桩侧负摩阻力及其受力特点的试验研*究

Experimental study on negative skin friction and mechanical behavior of high-speed railway CFG pile-raft composite foundation

通过京沪高速铁路CFG桩-筏复合地基的现场试验研究,获得了桩身弹性模量及路堤填筑过程及路基静置期间的桩身应变,分析了CFG桩身轴力和负摩阻力的变形规律。结果表明,在路堤填筑期间,负摩阻力就已经存在,桩身轴力随着深度的增加先增大后减小;静置期间,桩身负摩阻力和轴力仍有明显增长。桩身负摩阻力与路基填筑高度和固结时间密切有关。

According to the result of CFG pile - raft composite foundation test on high - speed railway, the down- drag of the piles were increased by the friction between the soil and the piles because of the pile - soil differential settlement, and the negative skin friction was generated. The negative skin friction increases the deformation of piles and even leads to the destruction of piles. Through the in - situ test of CFG pile - raft composite foundation on Beijing - Shanghai high - speed railway project, the pile elastic modulus was obtained and the change of the pile strain during embankment filling and＇subgrade standing was measured. The variation of the axial force of pile and the negative skin friction were analyzed. Test results show that the negative skin friction generates when the embankment is filled and the axial force of pile increases with the increase of depth and then decreases. The neg- ative skin friction and the axial force of pile still increase during suhgrade standing. The magnitude of the nega- tive skin friction of pile has closely relationship with the embankment height and consolidation time.