【作者】 孙波；

【导师】 王建华；

【作者基本信息】 上海交通大学 ， 岩土工程， 2008， 硕士

【摘要】 现在桩基础己经成为工程建设中应用最广泛的基础形式,桩基础在设计和施工中产生的负摩擦力也渐渐为人们所认识。国内外一些实测资料表明,桩基础在堆载作用下负摩擦力可能产生非常大的下拽荷载和沉降,其产生的不均匀沉降对基础危害最大。鉴于负摩擦力对桩基础应用过程中的重要影响,桩基础的负摩擦力己经成为基础工程界的一个技术热点。本文对确定单桩负摩擦阻力各种方法的优缺点进行了阐述,并对在设计阶段即考虑负摩擦阻力的必要性给予了论述。对单桩负摩擦阻力的产生原因、产生机理、建筑桩基规范中负摩擦阻力的确定方法、负摩擦阻力中性点位置的确定、以及对荷载传递基本微分方程的推导都进行了探讨。文中基于荷载传递函数的概念,提出了一种用双曲线模型来分析单桩荷载传递规律的方法。通过对大量单桩静载荷试验的反分析和统计研究,得到上海地区荷载传递函数参数的取值规律。研究发现,荷载传递函数参数符合正态分布,但其变异性比土的常规物理力学性质指标的变异性大,其中参数b的取值与桩侧极限摩阻力呈负相关。本文结合室内模型试验,通过不同的加载方式,研究有堆载与无堆载时单桩承载力特性的变化;并对试验数据进行反分析,得到了堆载作用下荷载传递函数参数取值的变化规律。反分析的结果表明,计算值与试验结果吻合得比较好,荷载传递法仍然适用于负摩擦桩。文章还通过现场原位测试,研究单桩受力变形规律及荷载传递特性;对比有堆载与无堆载的情况,分析负摩擦力对单桩承载力的影响。研究表明,堆载对于基桩会造成承载力下降、沉降增大等一系列不利影响,但其影响主要集中在浅层土体当中,对于深层土体影响不大,本次测试负摩阻力的影响深度为20m,中性点深度为9m。文中结合桩基荷载传递参数的统计规律,分析研究负摩擦桩荷载传递函数的各项参数取值,并与室内模型试验的结果进行对比,结果比较吻合。本文的研究结果,对于今后相关方面的研究具有一定的指导意义,并对类似工程的设计具有重要的参考价值。更多还原

【Abstract】 Pile foundation is one of the oldest foundation forms,and develop very rapidly in modernize era. Along with the piles technology’s development and construct skill bring forth the fresh,pile has became the broadest foundation forms in project item. The negative friction in pile’s designing and constructing is acquainted with for engineer. Many survey data refer to mortal down load and sedimentation be produced due to the negative friction in pile foundation. The inequable sedimentation endanger the pile foundation greatly. Due to the important infection in using foundation, the negative friction in pile has became one of the engineering skill focus.This paper describe different methods of determining single piles negative friction. The advantage and disadvantage of these methods are discussed. In engineering practice, negative friction must be considered to ensure the foundation stability. The factors that cause negative friction are discussed. The neutral point and negative friction are determined according technical code for building pile foundation.Load transferring concept, the author puts up with a method which uses hyperbolic model to analyze the load transfer mechanism of a single pile. The author utilizes hyperbolic model to back calculate parameters of pile load transfer curve from various sites of Shanghai are collected.Based on the concept of load transfer function, this paper advances a method which is used for analyzing single pile load transfer character by hyperbolic model. After many back-analysis and statistical research, the parameter picking rule of Shanghai area load transfer function is obtained.This paper studies bearing and deforming behavior of single pile and load transfer characteristic by indoor model experiment and in-situ test. analyses the single pile carrying capacity effect under negative friction by comparing two situation that with load or not. analyses various parameter value of negative friction pile load transfer function combined with the statistical rule of pile load transfer parameter.更多还原