软土地区超长桩承载特性的现场试验研究  

Field tests research on bearing characteristics of super-long piles in soft soil region

作　　者：李韬 LI Tao(SGID Engineering Consulting(Group)Co.,Ltd.,Shanghai 200093,China;Shanghai Engineering Research Center of Geo-Environment,Shanghai 200093,China)

机构地区：[1]上海勘察设计研究院(集团)有限公司,上海200093 [2]上海环境岩土工程技术研究中心,上海200093

出　　处：《建筑结构》2020年第21期114-120,共7页Building Structure

基　　金：上海市科学技术委员会工程技术研究中心建设专项(15DZ2251300)。

摘　　要：搜集软土地区近二十项工程七十余组超长桩试桩资料,对其承载特性进行深入研究,分析结果表明:桩侧土层性质和分布、施工因素、后注浆效果是影响承载特性的主要因素。根据单桩Q-S曲线特征,提出缓变型桩端后注浆超长桩极限承载力的确定标准;超长桩在最大荷载下的桩顶回弹率与单桩刚度总体呈指数关系,单桩刚度均值约为550kN/mm;超长桩混凝土单轴压缩弹性模量随荷载水平增大呈指数关系降低,提出考虑模量变化和承载性状发挥的超长桩桩身压缩量估算公式;不同荷载水平下,侧阻力沿桩身由菱形分布向梯形分布发展,工作荷载下可不考虑临界桩长问题;端阻比随最大加载量的增大而线性增大,采用后注浆工艺后超长桩端阻力发挥值未显著提高。By collecting more than 70 sets of super-long pile test information in nearly twenty projects,bearing characteristics of super-long pile has been studied in-depth.According to the analysis results,soil properties and vertical distribution,construction factors and post-grouting effect are the main factors affecting the bearing characteristics.Through the characteristics of Q-S curve of a single pile,the determination criteria of ultimate bearing capacity was proposed in which the Q-S curve of a super-long base-grouting pile was changed slowly.The rebound rate of pile top under ultimate load is the exponential relationship with the stiffness of a single pile,which the average value of stiffness is above 550kN/mm.The uniaxial compressive elastic modulus of concrete for super-long piles decreases exponentially with the increase of load level,at the same time the estimation formula of super-long pile compression was taken to consider changes in modulus and load characteristics;Under different load levels,the shaft resistance develops from the diamond-shaped distribution to the trapezoidal distribution in which the critical pile length is not considered under the working load state.The share of base resistance increases linearly with the increase of the maximum loading,however the development of top resistance of super-long piles after using post-grouting process did not significantly improve.

关 键 词：超长桩 承载特性 单桩极限承载力 桩身压缩量估算公式 端阻比 

分 类 号：TU473[建筑科学—结构工程]