Pile Cap and Cushion Effect Analysis of CFG Pile Composite Foundation Based on Field Test

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 further 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, 200 and 300 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 100 to 300 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 100 mm and pile cap diameter of 1.2 m.