【目的】柔性垫层和桩帽对CFG桩复合地基的桩土应力比、荷载分担比和沉降均有较大影响,但目前柔性垫层与桩帽在现场试验中如何共同影响复合地基特性仍有待进一步的研究。【方法】以CFG桩复合地基软基处理的某路段作为工程背景,在土工格栅层数不变的情况下,对垫层厚度为100mm、200mm、300mm,桩帽尺寸为0.8m、1.0m、1.2m组合下的形式进行了现场原位试验,研究了CFG桩复合地基的桩土应力比、荷载分担比和沉降特性。【结果】现场试验表明:随着垫层厚度由100mm增大到300mm,桩土荷载比减小了51.5%,桩土应力比减小了52.5%,总沉降量增大了7.9%;随着桩帽直径由0.8m增大到1.2m,桩土荷载比增大了29.0%,桩土应力比减小了29.2%,总沉降量10.4%.本文区域地质条件,宜选用垫层厚度100mm、桩帽直径为1.2m的CFG桩复合地基形式。

【Purposes】 The flexible bedding layer and pile cap have great influences on the pile- soil stress ratio, load sharing ratio, and settlement of CFG pile composite foundation, and fur- ther research is still needed about how the flexible bedding layer and pile cap jointly affect the characteristics of the composite foundation in field tests. 【Methods】 By using a section of CFG pile composite foundation with soft foundation treatment as the engineering background, field in- situ tests were conducted for the combinations of bedding thicknesses of 100, and mm and pile cap size of 0.8, 1.0, and 1.2 m under the control of constant number of geogrid layers to investigate the pile-soil stress ratio, load sharing ratio, and settlement characteristics of CFG pile composite foundation. 【Findings】 Field tests show that with the increase of cushion thickness from to mm, pile-soil load ratio decreases by 51.5%, pile-soil stress ratio decreases by 52.5%, and total settlement increases by 7.9%. As the diameter of pile cap increases from 0.8 to 1.2 m, the pile-soil load ratio increases by 29.0%, the pile-soil stress ratio decreases by 29.2%, and the total settlement is 10.4%. For the regional geological conditions in this work, it is advisable to choose the CFG pile composite foundation with cushion thickness of mm and pile cap diameter of 1.2 m.