灌注桩套管振动贯入过程模型试验及数值模拟
Model Test and Numerical Simulation of Penetration Process of Sleeve for Cast-in-Place Piles Driven by Vibratory Hammers

为了研究灌注桩套管振动贯入引起的施工效应，通过物理模型试验，对套管贯入过程及贯入过程中孔隙水压力、水平向挤土应力和土塞闭塞程度的变化规律进行了分析；建立了能够有效模拟灌注桩套管振动贯入过程的数值分析模型，并对物理模型试验进行大变形数值模拟及对比.研究结果表明：灌注桩套管贯入深度每增加0.2 m，超孔隙水压力和水平向挤土应力分别增加1 kPa和8 kPa，但挤土效应的影响范围主要集中在距离套管中心半径为6倍管径的范围内；由于套管壁与土体的反复剪切，产生不完全闭塞的土塞，套管端部形成环形土拱，此段土塞承担了80%的内摩阻力；随着套管直径增大，土塞闭塞程度由不完全闭塞过渡到完全非闭塞状态；套管贯入相同深度时，饱和砂土地基中土塞高度为干砂地基中土塞高度的1.2倍.
： A model test was carried out to investigate the excess pore pressure, the radial extruding stresses, and the degree of soil plug of a vibratory driven sleeve for cast-in-place piles. A finite element model was also introduced by using the commercial code, ABAQUS. The results from the finite element analysis are in a strong agreement with the experimental observations. The results show that the excess pore pressure and radial extruding stresses increase to 1 kPa and 8 kPa, respectively; nevertheless, the extruding effect is mainly limited within a radial distance of about 6 times the sleeve diameter. The soil shear strength and granular cementation force decrease during vibratory sleeve driving, which is induced by cyclic shearing action in the shear interface. As a result, the inside sleeve of the soil plug is in an incompletely plugged mode. During vibratory sleeve driving, the soil plug in the sleeve end forms an annular soil arch, which gives rise to an obvious increase in internal friction resistance. The soil plug of this section withstands 80%of the internal friction resistance. When the penetration depth is the same, the height of the soil plug in a saturated sand foundation is 1.2 times the height of the soil plug in a dry sand foundation. The vibration frequency, sleeve diameter, and saturation have significant effects on the soil plugging effect