Study On Installation And Bearing Capacity Character Of Jacked Pile

With the large-scale constructions of high-buildings and large complicated buildings, and the enhancement of environment protect requirements, jacked piles have been widely using in our country by the advantages of cheapness, reliability and convenience. But its research lags behind the application. This paper is based on theory study, prototype test, and apply flac3D numerical simulation soft ware. The penetration mechanism, settlement character, bearing capacity and other attractive topics are relatively deeply studied in this paper, which will offer sufficient base and evidence for further research and engineering application. The main studies of this paper are as following:(1) On the basis of deep studies and analyses of penetration mechanism of jacked pile, computational simulation method of jacking force based on spherical cavity expansion theory and friction fatigue effect is presented. In this method, the expansion of a series of spherical cavities is used to simulate the process of pile installation, lateral friction and end-bearing capacity are confirmed respectively, and lateral friction fatigue is fully considered, so the computation of jacking force are more consistent with real condition.(2) Lateral friction fatigue is evident through the penetration of jacked pile that has been discovered by test, which is discussed from two aspects of radial stress and friction angle; simulational computation formula of friction fatigue is confirmed, and the computation curve is studied; the law of friction fatigue of different geology condition is summarized by prototype tests in Tai Yuan and Zhu Hai.(3) The bearing capacity will be improved after penetration, which is called "time effect" and is analyzed from three aspects of soil consolidation, disturb-restore property and shell-effect. The mechanism of time effect mostly depends on the effect of pore pressure dissipation and effective stress increase, by which stimulation computation method of bearing time-effect in saturated soil is presented; the law of jacked pile bearing capacity improvement is studied in different geology condition of Zhuhai and Taiyuan by re-pressed tests, and effective forecast function expression is presented by regression analyse.(4) FLAC3D numerical simulation software is based on Lagrange computation method, which is fit for resolving large stain model, nonlinear and unstable problems of geotechnical engineering. In this paper, the bearing capacity character of jacked pile is simulated by FLAC 3D software, the result agrees well with the previous theories and test phenomena, and simulation effect is reasonable.