Abstract: According to longtime monitor on residual strain states of two large-diameter rock-socketed cast-in-place piles (dig by hand) before loading, inducing factors and distribution rules of residual strain, and its influence on bearing behaviours of pile are analyzed, some conclusions are obtained as follows: (1) the main factor of inducing residual strain is drying shrinkage of concrete; (2) the residual strain distribution of the two piles are regularly changing with space and curing time, but some construction factors, such as blowing up, groundwater and type of casting pile, will disturb residual strain distribution or soften restricting force which comes from rock beside pile side. (3) local strain of piles can exceed ultimate tensile strain of concrete, which can result in crazing of concrete and losing of capability of protection to reinforcement bar, and the shrinkage of the whole pile will decrease contact force between pile bottom and rock. The foregoing conclusions provide reference to engineering practice.

Key words: large-diameter, rock-socketed piles, drying shrinkage, residual strain, temperature