预应力锚索锚固力检测方法研究

发布时间：2019-01-22 15:42

【摘要】：作为岩土加固、稳定结构的最经济、高效的方法,岩土锚固技术诞生之日起就得到了工程技术人员的亲睐。不当的施工工艺及运营管理会把预应力锚索变成一个可能使工程毁于一旦的“定时炸弹”,因此预应力锚索锚固质量也一直是人们关注的焦点问题,而作为衡量锚索的锚固质量的重要参数——锚下有效预应力(锚固力)自然也受到人们的关注。但是岩土锚固工程属于长期、隐蔽工程,这给锚下有效预应力(锚固力)的检测带来了一定的困难。探索高效、准确、经济实用的检测方法,成为摆在岩土工作者面前的一个课题。因此,本文立题对此开展研究。本文对锚索预应力的损失机制展开研究,主要研究了预应力锚索内锚固段荷载分布、锚索失效和锚索预应力损失的影响因素。首先,在前人研究的基础上,研究了第一粘结面和第二粘结面的剪应力分布模式,两个粘结面的剪力分布模式有较明显差异:剪切应力的峰值及其位置均不相同;然后,根据现有的工程调研资料分析了五种不同的锚索失效形式:外锚固段失效、锚束体断裂、第一粘结面滑移破坏、第二粘结面滑移破坏、被加固岩土体破坏;最后,通过分析预应力损失的影响因素,得出了锚下有效预应力(锚固力)的理论计算公式sde-=NNN0,为有效预应力判定标准的制定提供参考。针对工程实践中对锚索预应力的检测只注重整个锚索的预应力,对锚索中每根钢绞线的预应力的不均匀情况较少涉及的情况,本文提出了不均匀度的概念,并通过两种不同的反拉方法——整体反拉法和分组反拉法——对此展开理论和试验研究。首先,详细分析了反拉法检测过程中锚束体应力-应变变化关系,建立锚索有效预应力判定标准;然后根据工程实践和理论分析,对现行技术规范《公路桥涵施工技术规范》中关于有效预应力合格标准的表述提出自己的见解;最后,通过现场的试验对分组反拉法的检测精度、对钢绞线应力不均匀度、有效预应力合格标准进行研究。本文对基于声弹性理论的无损检测方法的工程可行性进行了初步讨论。首先,对该无损检测方法的两个关键问题——声弹性系数确定和弹性波的选择——进行了讨论;接下来,通过对试验数据的处理和分析,验证了该无损检测方法的工程可行性;最后,对无损检测方法的检测精度影响因素和在工程中的应用前景进行讨论。
[Abstract]:As the most economical and efficient method to strengthen and stabilize the structure of rock and soil, the Anchorage technology of rock and soil has been favored by engineers and technicians since its birth. Improper construction technology and operation management will turn the prestressed anchor cable into a "time bomb" which may destroy the project. Therefore, the quality of prestressed anchor cable anchoring has always been the focus of attention. As an important parameter to evaluate the anchoring quality of anchor cables, the effective prestress under anchor (anchoring force) is also concerned by people. However, geotechnical anchoring works belong to long-term and hidden projects, which bring some difficulties to the detection of effective prestressing force under anchors. It has become a subject for geotechnical workers to explore efficient, accurate and economical detection methods. Therefore, this article raises the topic to carry on the research to this. In this paper, the loss mechanism of prestressed cable is studied, and the factors influencing the load distribution, the failure of anchor cable and the prestress loss of prestressed cable are studied. Firstly, on the basis of previous studies, the shear stress distribution modes of the first and the second bonding surfaces are studied. The shear stress distribution modes of the two bonding surfaces are obviously different: the peak value and the location of the shear stress are different; Then, according to the existing engineering investigation data, five different failure forms of anchor cable are analyzed: failure of external anchoring section, fracture of anchor body, slip failure of the first bond plane, slip failure of the second bond surface, and failure of the strengthened rock and soil; Finally, by analyzing the influencing factors of prestress loss, the theoretical calculation formula of effective prestress under anchor (Anchorage force) is obtained. Sde-=NNN0, provides a reference for the determination of effective prestressing force. In view of the fact that the detection of anchor cable prestress only pays attention to the prestress of the whole anchor cable in engineering practice, and the non-uniformity of the prestress of each steel strand in the anchor cable is less concerned, the concept of non-uniformity degree is put forward in this paper. The theoretical and experimental studies are carried out through two different backpull methods, the global backpull method and the group backpull method. Firstly, the relationship between stress and strain of Anchorage is analyzed in detail, and the criterion of effective prestress of anchor cable is established. Then according to the engineering practice and theoretical analysis, the author puts forward his own opinion on the expression of the qualified standard of effective prestress in the current technical code of highway bridge and culvert construction. Finally, through the field test, the test accuracy of the group back pull method, the stress inhomogeneity of steel strand and the qualified standard of effective prestress are studied. In this paper, the engineering feasibility of nondestructive testing method based on acoustic elasticity theory is discussed. Firstly, two key problems of the NDT method, namely, the determination of acoustic elastic coefficient and the selection of elastic wave, are discussed, and the engineering feasibility of the NDT method is verified by processing and analyzing the test data. Finally, the influencing factors of nondestructive testing method and its application prospect in engineering are discussed.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416

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