夯扩碎石桩群桩承载性状研究  

Research on Bearing Behavior of Rammed Aggregate Pier Group

作　　者：陈建峰[1,2] 韩杰[3] 

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]同济大学岩土及地下工程教育部重点实验室,上海200092 [3]堪萨斯大学土木、环境与建筑工程系,堪萨斯劳伦斯KS66045

出　　处：《中国公路学报》2010年第1期26-31,共6页China Journal of Highway and Transport

基　　金：国家自然科学基金项目(50508030);上海市重点学科建设项目(B308)

摘　　要：对2个初始直径为0.76m、桩长为2.79m和5.10m的夯扩碎石桩群桩进行载荷试验,并采用三维拉格朗日有限差分程序建立数值模型,模拟其夯扩和载荷试验分级加载过程,并分析了桩土应力比、群桩效应和桩间土单元的应力路径。结果表明:数值分析很好地模拟了夯扩碎石群桩的夯扩过程,群桩夯扩成桩后最大垂直位移位于桩间土中心且表现为地面隆起;计算和实测的荷载-沉降曲线基本一致;2个不同桩长的夯扩碎石桩群桩在各级荷载下的桩土应力比都比较接近,其值在3.8～6.5之间;群桩效应跟桩长与承台宽度比L/Bc相关,群桩负效应随L/Bc的增大而减弱;2个不同桩长的群桩桩间土单元在夯扩过程中其水平应力大于垂直应力,单元应力处于临界破坏状态;夯扩作用在桩间土中产生预应力,提高了土体刚度和夯扩碎石桩的承载能力,靠近桩端的土体单元预应力受桩端夯扩效应影响而增大。Loading tests on two rammed aggregate pier group （RAPG） with initial diameter of 0.76 m, initial lengths of 2.29 m and 5.10 m respectively were carried out. A three dimensional Lagrange finite difference process was used to simulate the installation and loading process of loading test classification. Pier soil stress ratio, pier group effect and stress paths of two soil elements at different depths among the piers were also analyzed. The results show that the numerical model well simulates the installation of pier group. The maximum vertical displacement is located at the center of the RAPG and which shows ground heaving. The computed loading-settlement curves for two RAPG are close to the measurement curves. Pier-soil stress ratios at each loading for two RAPG are close and the value range is from 3.8 to 6.5. Effect is related to the ratio of the pier length and the base slab width. Pier group negative effect decreases with the increase of the ratio. Horizontal stresses are greater than vertical stresses for two soil elements at different depths among the piers during installation of RAPG and the stress levels are in the critical failure state. The installation of piers results in prestress in soil elements among the piers. Therefore, the soil stiffness and bearing capacity of RAPG is increased. Prestress in the soil element closing to the piers＇ bottom which is affected by the rammed effect to the bottom is increased.

关 键 词：道路工程 夯扩碎石桩 载荷试验 群桩 地基处理 数值分析 

分 类 号：U416.1[交通运输工程—道路与铁道工程]