In-situ Test of Pile-soil Stress Ratio of CFG Pile-net Composite Foundation in Beijing-Shanghai High-speed Railway

Pile-soil stress ratio is one of important parameters in the design of high-speed railway composite foundation. The full scale in-situ test in trial section of Beijing-Shanghai highspeed railway by adopting composite foundation of CFG pile-net (geogrid) with preloading was carried out. The magnitude of the pile-cap head vertical stress, soil stress among piles, pile-soil stress ratio and their variations with filling height and consolidation time were measured. The variation of pile-soil stress ratios with subgrade cross-section was analyzed. The measured results show that the pile-soil stress ratio is closely related to filling height and changes a little with consolidation time when the filling height is kept constant. In the central area of subgrade, the pile-soil stress ratios are in the range of 5 to 6. And the CFG piles (caps) and soil in composite foundation can together play a role in the whole cross-section to bear the filler load. The conclusions can provide valuable preference for the design of the CFG pile-net composite foundation under embankment in China high-speed railway.