Study of key technologies of vacuum negative-pressure static pile load test

The conventional static pile load testing methods include Kentledge, reaction piles and bi-directional methods, whereas each of these methods has inevitable disadvantages. A vacuum static load testing is developed to avoid the disadvantages of these traditional methods. A set of reaction devices is designed for vacuum negative-pressure static pile load test, which can be used in engineering practice. Pile foundation loading and vacuum negative-pressure static load tests were carried out. Vibrating wire rebar stress meters, earth pressure cells and displacement bar monitoring sensors are installed on the pile. The effective sealing reaction system is formed by referring to the measures of foundation vacuum preloading drainage preloading sealing system. The Q-s curve, s-lgt curve, the distribution of axial force, lateral resistance and terminal resistance in the loading process of the tested pile are analyzed. The tests show that the response of lateral friction of the pile is closely related to the vacuum pumping process. Due to the stiffness, pressure transfer and sealing effect of the negative pressure platform, there is a certain gap in the maximum loading magnitude between the vacuum negative-pressure and the related theoretical value. The corresponding solutions and improvement measures are proposed for the above problems.