桩-筏(网)复合地基桩土应力比现场测试研究

Field experiment of pile-soil stress ratio of pile-raft (net) composite foundation

桩土应力比是刚性桩复合地基的一个重要设计参数,通过对沪宁城际铁路路基试验段CFG桩-筏(网)和PHC桩-筏复合地基桩土应力进行长期观测,分析了桩土应力变化规律,对桩土应力横向分布、桩间土应力变化、桩土应力比及荷载分担比等进行了对比研究。研究表明:桩土应力比与填筑荷载成非线性关系,与桩土相对刚度密切相关;桩土应力横向呈不规则锯齿形分布,桩顶应力集中现象明显,桩间土承载作用在填筑初期得到了充分发挥,桩土差异沉降迫使桩顶承受更多荷载,褥垫层和土工格栅调整了桩土荷载分担,揭示了路堤荷载作用下桩-筏(网)复合地基承载机制。

Pile-soil stress ratio is an important design parameter in rigid pile composite foundation,through long-term observation of CFG pile-raft（net） composite foundation and PHC pile-raft composite foundation changes of pile-soil stress ratio were obtained by field test.Analysis of pile-soil stress variation and comparative study of the lateral distribution of pile-soil stress,pile-soil stress variation,pile-soil stress ratio and load sharing ratio,etc.The results indicate that pile-soil stress ratio increases with the non-linear relationship between load filling,pile-soil relative stiffness and pile-soil stress ratio is closely related to;Lateral pile-soil stress distribution is irregular zigzag and clear stress concentration formed in the top of the pile,in the early filling,soil between piles bear more load,then pile-soil differential settlement and geogrid cushion and adjust the pile-soil load sharing cause the pile to bear more load,pile-raft（net） composite foundation bearing mechanism under embankment load is revealed.