Abstract：Due to the large-scale vertical loads，a relative movement can be induced when the soil settles in relation to the pile. Thus，the negative skin friction occurs if the movement of pile is upward.Taking the in-situ test of negative skin friction on punched cast-in-place pile of Ninghai Power Plant Project for example，the influence of the soil consolidation around pile on the downdrag forces and the position of neutral point are studied. Different subsurface soil settlements are measured within and outside the two sets of piles，suggesting different influential degrees of the piles on the surrounding soil. The positions of the neutral point obtained from the measured settlement curves of soils and piles agree with the ones from the variable curve of pile axial force with depth. The measured maximum coefficients of side skin friction around piles are consistent and they vary between 0.3 and 0.4. Furthermore，based on the test results，the effect of pile construction technology on negative skin friction is analyzed. It is commended that the calculation of the settlement distribution is emphasized in the design for the negative skin friction piles. These conclusions are useful for engineering practice，which may guide the design and construction of similar projects.
