Abstract: The researches on sinking characteristics of jacked pile in clayey soil are relatively few. In this study, variations of pile sinking resistance, axial force and unit skin friction during jacked pile sinking were studied based on fiber Bragg grating sensing technology, considering the different pile end forms (such as open-ended and close-ended pile) and different pile diameters. Jacked pile sinking model tests were performed to determine the influences of pile ending form, pile diameter and pile sinking depth on pile sinking resistance, axial force and unit skin friction. The results shows that the requirement of FBG technology shows superior performance in testing sinking resistance of jacked piles in clayey soil, which can accurately reflect the penetration characteristics of jacked piles. The end resistance of open-ended and close-ended piles accounts for 66.7% and 59.5% of the piling resistance, respectively when sinking pile ends. The effects of open soil plug effect and pile diameter on pile sinking resistance can not be neglected. The distribution of the axial force of the pile shaft is not changed due to the pile end forms. The axial force transmission performance of pile with a diameter of 140 mm is better than that with 100 mm pile diameter. The decline rate of the axial force of the two piles is 40.8% and 34.2%, respectively. The maximum unit skin friction of the inner and outer tube piles of the open-ended pile is 1.67 kPa and 4.83 kPa, respectively, which are smaller than that of the close-ended pile. When the sinking depth is 90 cm, the maximum unit skin friction of the pile increases with increasing the pile diameter, and the larger pile diameter at the same depth results in more obvious degradation of the unit skin friction of the pile.

Key words: jacked pile, FBG sensing technology, sinking resistance, axial force, unit skin friction