摘 要

桩基是一种古老的基础型式，是目前应用最广泛的基础形式。桩工技术经历了几千年的发展过程，无论是桩基材料和桩类型，或者是桩工机械和施工方法都有了巨大的发展，已经形成了现代化基础工程体系。在某些情况下，采用桩基可以大量减少施工现场工作量和材料的消耗。随着我国建筑行业的快速蓬勃发展，对各种桩基础的需求量也越来越大。如何确定单桩承载力，减少试桩实际承载力与设计值之间的误差，成为目前工程中一个重大问题。显然，传统的静载试验已不能满足试桩要求。因此，自平衡法应时而生。自平衡法作为一种先进高效的静载试验技术，打破了传统桩基检测方法耗时耗力耗场地的局限，弥补了传统静载试验的不足，适用于不同条件下的试桩要求。截至目前，自平衡法已被广泛运用到国内外实际工程中。

本文从实例出发，结合国内外的经验和工程实例，对自平衡法在大直径桩中检测做一个介绍和分析，具体内容如下：

（1）介绍几种桩基承载力检测方法，并分析比较他们的优缺点。

（2）归纳总结自平衡法的工作原理、荷载箱位置的确定、常用的埋置位置以及检测流程。

（4）分析单桩竖向承载力的影响因素，分析自平衡测试法试桩与传统试桩的工作机理的区别，探讨了自平衡试桩极限承载力的转化方法。

（5）结合正在建设的漳州马洲大桥项目，从实际工程中探究自平衡法的可行性。

本文以正在建设的漳州市东环城路及其接线工程A3合同段马洲大桥为工程背景，开展大直径桩基自平衡法试验的检测研究。首先对试验桩基加载试验值的计算复核，根据地勘单位提供相关钻孔记录及地基土参数计算相关桩基侧摩阻力及端承阻力值。其次按自平衡法试桩原理进行计算，确定平衡点及钢筋应力计的安装位置。钢筋笼在加工制作过程中，及时将荷载箱及应力计的安装设计位置。最后通过静载仪等采集仪对试验数据的采集和分析。

关键词：自平衡法；承载力；大直径桩；桩基检测

Abstract

Pile foundation is an ancient basic type and is the most widely used basic form. The pile-driving technology has experienced thousands of years of development. Whether it is pile-based materials and pile types, or pile-driving machinery and construction methods have developed tremendously, a modern basic engineering system has been formed. In some cases, the use of pile foundations can significantly reduce the workload on the construction site and the consumption of materials. With the rapid development of China's construction industry, the demand for various pile foundations is also growing. How to determine the bearing capacity of a single pile and reduce the error between the actual bearing capacity of the test pile and the design has become a major problem in the current project. Obviously, the traditional static load test can not meet the test pile requirements. Therefore, the self-balancing method should be born from time to time. As an advanced and efficient static load test technology, the self-balancing method breaks the limitation of the traditional pile-based detection method, which takes time and effort, and makes up for the shortcomings of the traditional static load test. It is suitable for test pile requirements under different conditions. Up to now, the self-balancing method has been widely used in practical engineering at home and abroad.

Based on the examples, combined with domestic and foreign experience and engineering examples, this paper introduces and analyzes the self-balancing method in large-diameter piles. The specific contents are as follows:

(1)Introduce several pile foundation bearing capacity detection methods, and analyze their advantages and disadvantages.

(2) Summarize the working principle of the self-balancing method, the determination of the position of the load box, the commonly used embedding position and the detection process.

(3) Analyze the influencing factors of the vertical bearing capacity of single pile, analyze the difference between the working mechanism of the self-balance test and the traditional test pile, and discuss the transformation method of the ultimate bearing capacity of the self-balanced test pile.

4)Investigate the feasibility of the self-balancing method from the actual project in combination with the Zhangzhou Mazhou Bridge project under construction.

This paper takes the Mazhou Bridge in the A3 contract section of the Dong huan Road and its connection project in Zhangzhou as the engineering background, and carries out the test research on the self-balancing test of large-diameter pile foundation. Firstly, the calculation of the test value of the test pile foundation is reviewed. According to the relevant drilling records and the ground soil parameters, the lateral friction resistance and the end bearing resistance value of the pile foundation are calculated according to the geological survey unit. Secondly, according to the principle of self-balancing test pile, the balance point and the installation position of the steel stress gauge are determined. In the processing and manufacturing process of the steel cage, the installation position of the load box and the stress gauge is timely. Finally, the collection and analysis of the test data is performed by a static load meter or the like.

Key words: self-balancing method; bearing capacity; large diameter pile;pile foundation inspection

目 录

第1章 绪论 1

1.1 课题的提出和研究意义 1

1.2 国内外研究现状和存在的问题 1

1.2.1 国内外研究现状 2

1.2.2 存在的问题 3

1.3 主要研究内容 3

第2章 传统桩基检测技术和单桩竖向承载能力 5

2.1 传统桩基检测 5

2.1.1 桩基静载试验 5

2.1.2 低应变法 6

2.1.3 声波透射法 6

2.1.4 高应变法 7

2.1.5 钻芯法 7

2.2 单桩竖向承载力 7

2.2.1 单桩竖向极限承载力构成 7

2.2.2 影响单桩承载力的因素 7

2.2.3 单桩荷载传递特性 9

第3章 自平衡测试技术 11

3.1 自平衡法的基本原理 11

3.1.1 基本原理 11

3.1.2 试验装置 12

3.2 平衡点位置确定及荷载箱埋置位置 14

3.2.1 平衡点位置的确定 14

3.2.2 荷载箱埋置位置 15

3.3 自平衡法与传统检测技术的比较分析 17

3.3.1 自平衡法与传统法的异同点 17

3.3.2 自平衡法的优势 18

3.4 自平衡试验测试准则 18

3.4.1 测试时间 18

3.4.2 实验数据处理分析方法 19

3.4.3 自平衡试验法试桩承载能力确定 20

第4章 自平衡试验法工程应用 22

4.1工程实例 22

4.1.1 概述 22

4.1.2 试桩目的及试验依据 26

4.1.3 试桩基本情况 27

4.2 平衡点计算 28

4.3现场安装 31

4.3.1荷载箱及相关配件运抵现场 31

4.3.2组合式荷载箱上下导流体预浇筑混凝土 31

4.3.3组合式荷载箱与钢筋笼焊接 32

4.3.4下放钢筋笼及灌注桩身混凝土 34

4.4 现场检测 36

4.4.1前期准备 36

4.4.2搭设基准梁、基准桩 36

4.4.3准备电源 37

4.5加卸载方式及终止加载条件 37

4.5.1 加卸载方式和位移观测 37

4.5.2 终止加载条件及极限加载值 37

4.6 试验结果 38

第5章 结论与展望 41

5.1 结论 41

5.2 展望 41

参考文献 43

致谢 45

第1章 绪论

• 1. 课题的提出和研究意义

桩基础是一种历史悠久的基础形式，它的作用是将所承受的的上部荷载压力传递到土体，以满足工程的需求。桩基础可以分为端承桩和摩擦桩，广泛地运用到各个工程，尤其是高层建筑中。随着生活水平和施工工艺的提高，大型桥梁、高层建筑越来越多，它们对桩基础的要求也越来越高。因此迫切的需要对桩基础进一步的研究和改进以满足工程项目的大型化。而目前最常见的就是大直径钻孔灌注桩。

大直径钻孔灌注桩具有以下特点：