Load transfer mechanism and failure characteristics of piles embedded in soft rock

Based on a large number of field pile loading tests, the bearing characteristics of rock-socketed piles are analyzed. The statistics show that the rock-socketed piles mainly present as end-bearing friction ones and also have the properties of frictional end-bearing piles or end bearing piles under test load. The exertion of shaft resistance and end resistance is asynchronous, that is, the shaft resistance exerts prior to the end resistance, so, it is necessary to take different safety factors respectively to design the vertical bearing capacity. The rock-socketed piles have characteristics of sudden failure for two reasons: pile damage and socket section damage, including the interface of rock and piles and the surrounding rock. Field pile test data show that, even embedded in soft rock, the failure mode is usually presented as pile damage, so the control action of pile strength should be considered while conducting the design of rock-socketed piles. Finally, the calculation formulas in the existing norms are analyzed, and some unreasonable points are pointed out.