基于透明土的梅花桩沉桩挤土效应

Plum-blossom Pile Penetration Effect Based on Transparent Soil

为研究梅花桩沉桩挤土效应,开展了一系列梅花桩沉入透明土的模型试验.结合透明土和粒子图像测速技术,采用静压桩方法研究了梅花桩沉桩过程中不同阶段桩周土位移变化特征.根据圆孔扩张理论和梅花桩的几何特性,建立了一种简单的修正圆孔扩张理论,用于分析梅花桩的沉桩挤土径向位移的分布规律以及挤土效应影响范围,同时利用数值计算方法建立了梅花桩的沉桩挤土效应分析模型.通过与梅花桩模型试验结果及修正扩孔理论分析结果进行对比,验证了本文所提出的修正圆孔扩张理论的正确性和可靠性,揭示了梅花桩沉桩过程中桩周土体的径向位移变化规律.研究结果表明,梅花桩静压沉桩挤土过渡区约为等截面圆形桩的1.5倍,圆孔扩张区的挤土效应与等截面圆形桩的沉桩挤土效应规律基本一致,梅花桩静压沉桩时桩端阻力、桩侧摩阻力和整体沉桩阻力分别是等截面圆形桩的1.0倍、1.38倍和1.12倍.

In order to get the penetration effect of plum-blossom piles,a series of model tests of plum-blossom piles penetrating transparent soil was carried out. Combined with transparent soil and particle image velocimetry,based on the static pressure pile method,the displacement characteristics of soil around the plum-blossom pile in the process of jacked-pile penetration in different stages were studied. According to the cylindrical cavity expansion theory and the geometric characteristics of plum-shaped piles,a simple modified cavity expansion theory is proposed to compute the radial displacement induced by the pile penetration and the influence range of penetration effect of plum-shaped piles. At the same time,an analysis model of the penetration effect and cavity expansion of plum-shaped piles is proposed by using a numerical calculation method. By comparing the test results of the transparent soil test and the analysis results of the modified cavity expansion theory,the modified cavity expansion model is validated,and the penetrating process of plum-shaped piles and round piles with equal cross sections is compared. The results show that the soil compaction transition zone of a plum-blossom pile is about 1.5 times that of a circular pile with equal cross section,and the penetration effects of a plum-blossom pile are similar to those of traditional equal section circular pile in cavity expansion area. The pile driving tip resistance,pile shaft and total resistance of tapered pile equal 1.0 times,1.38 times and 1.12 times of those of equal section circular pile respectively.