黏性土中静压沉桩贯入力学机制室内试验研究

For open-ended jacked pipe pile, the pile body is subjected to complex forces during pile jacking, especially the soil plug resistance caused by soil plug effect inside the pile body, which has a significant influence on the pile side resistance. Therefore, it is of great significance to carry out a comprehensive experimental study on the mechanical mechanism of jacked pile and the side resistance separation of open-ended pipe pile for the construction and bearing capacity determination of jacked pile. The influence of the pile end form on the pile penetration mechanism in the homogeneous cohesive soil layer was discussed by means of laboratory model tests. Based on the development of the double-wall open-ended model pipe pile, and combining utilization of sensitized fiber Bragg grating strain sensor and double-diaphragm temperature-self-compensating fiber Bragg grating earth pressure sensor, the “soil plug resistance” implied in the pile jacking resistance was separated, and the variation rules of axial force and pile jacking resistance of the pile during the penetration of open-ended pipe pile were obtained. The test results showed that the different pile end forms not only affected the development of pile end resistance, but also had a significant influence on pile side resistance. With the increase of depth, the axial force of the close-ended pile decreased continuously, and the decline rate of axial force acting on the open-ended pile far from the pile end increased gradually, and the axial force near the pile top was basically 0. The unit pile side resistance continued to increase with depth, and the degree of unit pile side resistance of the open-ended pile external pipe pile body was less than that of the close-ended pile. At the same depth, with the increase of penetration depth, the unit pile side resistance decreased continuously, i.e., the phenomenon of "side resistance degradation". Moreover, with the increase of penetration depth, the unit pile side resistance at this position decreased more, which was consistent with the existing research conclusions on the mechanical properties of jacked pile penetration. The research results can provide references for the construction design of jacked pile in cohesive soil.