桥梁挤扩支盘桩沉降分析与抗变形能力

Settlement Analysis and Deformation Resistance of Piles with Branches and Plates for Bridges

挤扩支盘桩抗变形能力主要依赖于挤扩过程中支盘周围土体模量的增长、挤扩增大端承面积实现应力扩散、桩长缩短减小桩身压缩量等几个因素。对潮汕环线11组静载试验(6组常规桩、5组支盘桩)的Q-s曲线进行了分析,支盘桩表现为小变形、缓变型、高回弹率等特征。选取了典型的试桩结果进行了反分析,得出挤扩作用使得周围土体模量增长约1倍左右的结论。在此基础上,对桩端变形与桩端应力分布规律、桩身压缩量变化规律进行了分析,弹性受力阶段,桩身压缩量约占支盘桩总沉降的40%~50%。通过潮汕环线现场沉降监测的初步数据,说明了挤扩支盘桩的变形控制能力:箱梁架设完成后支盘桩的观察时间为60~120d,沉降为3~6mm;常规桩观察时间约30d,沉降为5~9mm,支盘桩的沉降小于常规桩,变形控制能力更强。

The anti-deformation ability of piles with branches and plates mainly depends on several factors,such as the increase of modulus of soil around the branches and plates because of extrusion effect,the stress diffusion by muti-expanding end effect,the shorter of pile length and the reduction of pile compression.In the paper,11 groups of static load tests Q-s curves(including 6 groups of conventional piles and 5 groups of piles of branches and plates)on Chaoshan Loop Line Expressway have been analyzed.Being compared with conventional piles,piles with branches and plates are characterized by small deformation,slow deformation and high rebound rate.It has been concluded that the modulus of surrounding soil increases by about one time due to extrusion effect by analyzing typical pile test results.In the stage of elastic force,the compression of pile body accounts for 40%~50%of the total settlement of branch and plate pile.The settlement branch and plate pile is 3-6mm during 120d observation period.While the settlement of conventional pile is 5-9 mm during 30d observation period,which is more than that of branch and plate pile.So the deformation control ability of pile with branches and plates is better.