Journal of Engineering Geology工程地质学报1004-9665/2013/21(4)-0577-06
砂土地层中桩基受力特征试验分析
许崧阎长虹许宝田
(南京大学地球科学与工程学院南京210093)
摘要我国长江中下游沿岸地基中分布有较厚的砂土层,砂土层是桩基的良好持力层。该地区
砂性土埋疲浅,厚度大,往
往夹杂粉土或粉质黏土,…般随深度增大,砂土变密实。已有研究成果中,针对桩身穿过多层砂土条件下柱基承载力的研究
较少。砂土地基中打入桩试验结果表明,砂性土的状态对打入式预制柱的施工产生很大的影响,在松散或稍密的砂性土中沉
柱一般比较容易,而在中密或密实的砂性土中则较为困难。本文通过某电厂工程灌注桩现场静载试验,研究了砂土地基中桩
身沉降随荷载变化规律,分析了桩身轴力随地层深度变化特征及不同土层的桩侧摩阻力。设计钴孔灌注桩桩径为800mm,桩
长为47.2m,桩身混凝土强度等级为C35,桩身穿过9层土层,由现场3根桩静载试桩结果可知,荷载与沉降关系呈非线性,
Q-s曲线分为弹性阶段、弹塑性阶段和整体破坏3个阶段,15m深度以下的粉细砂层侧摩阻力对柱身轴力影响较大,15m以
上粉质黏土和淤泥质土对桩轴力影响较小。根据Q-s曲线确定单桩极限载荷约为4800~5400kN,平均值为5201kN,可满足
设计要求,地基中下部砂土层承载力较大,砂土侧摩阻力大于黏性土的侧摩阻力,最大可达到70kPa。所得结论可为该类地基
进一步的理论研究及工程设计提供有益的参考。
关键词砂土桩基静载试验桩側摩擦阻力
中图分类号:TU473.1文献标识码:A
IN- SITU TEST AND ANALYSIS ON MECHANICAL CHARACTERISTIC
OF PILES IN SANDS
XU Song YAN Changhong XU Baotian
School of Earth Science and Engineering of Nanjing University, Nanjing 210093)
Abstract Large number of engineering practice shows that there are thick sand layers in the foundation along the
middle and lower reaches of the Yangtze River, China. The sand layers are good bearing stratum for pile founda
tions. In the area, the sands are at shallow depths, have big thicknesses, and include silt and silt clay. As the
depth increases, the sands become dense. The experimental results of the driven piles indicate that the status of the
density of sands has great influence on the construction of the performed piles. The pile-driving operation is easier
in the loose or slightly dense sands than in the medium or very dense sands. In this paper, large scale static load
tests are carried out for three piles of a power station. The characteristics of the pile settlement with load variation
are studied. The axial force and side resistance of the piles are calculated at the same time. The designed diameter
of the three piles is 800mm, and their length is 47. 2m. The grade of the concrete is C35. Nine soil layers are pas
sed through by the pile body. The results of static loading tests indicate that the relation of the load() and settle-
收稿日期:2012-08-20;收到修改稿日期:2012-10-31.
基金项目:2008年度高等学校科技创新工程重大项目培育资金项月(708043)资助
第一作者简介:许崧,主要从事岩土力学方而的研究工作.Email:xubt@uju,edu.cn
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