过渡段地基加固作用对桥台桩工作性状的影响分析

摘要

A series of 3D centrifugal model tests and numerical analysis were carried out to investigate the effects of foundation reinforcement (pile spacings were 3d, 4d, 5d, 6d,d was diameter of CFG pile) of approach embankment on behaviors of abutment piles on soft clay. The results show that, behaviors of settlement of soft soil are changed by CFG deep transferring function of load vertically, CFG piles generate significant shield effect on lateral displacement of soft soil horizontally. When CFG pile spacing increases, the neutral point of abutment piles subjected to negative skin friction shifts down and the maximum of axial force increases, so does the pile tip resistance. The location where the maximum of the bending moment(the most dangerous cross section) occurs transfers from 1/2 pile length to pile head, whose value increases with the increase of the CFG pile spacing. The distribution of shear force along the pile length corresponds approximately to "anti-S" shape, inflection points occurs at both interface of soil layers and plane of CFG pile end. With the increase of CFG pile spacing, shear force at interface of soil layers increases while one at plane of CFG pile end decreases. Lateral displacement of abutment piles increases rotarily at a fixing point and the flexural deformation is more significant with the increase of CFG pile spacing. The property of creep of soft soil is inhibited by the existence of CFG piles compared with natural foundation.%为研究过渡段地基加固作用(桩间距为3d,4d,5d和6d,d为CFG桩径)对邻近桥台桩工作性状的影响,进行离心模型试验及三维数值模拟.研究结果表明:过渡段地基加固作用对桥台桩受力变形影响表现为在竖向上利用CFG桩荷载深层传递作用改变软土地基沉降变形特性,在水平方向上CFG桩对软土的侧向流动起显著阻拦作用;随着CFG桩间距增大,受负摩阻力作用的桥台桩中性点位置下移,最大轴力增大,桩端阻力随之增大;桩身弯矩最大值随CFG桩间距增加而增大,其位置(最危险截面)从桩长1/2处逐渐转移至桩顶;桩身剪力分布大致呈"反S"型,2处拐点分别位于土层界面及CFG桩端平面,且随着CFG桩间距增加,土层界面处桩身剪力增大而CFG桩端平面处剪力减小;桥台桩水平位移随桩间距增加以一固定点呈旋转式增大,桩身挠曲也越明显,而桥台转角及水平位移随桩间距近似线性增加;与天然地基相比,CFG桩在一定程度上限制了路基荷载下土体蠕变特性的发挥.