【作者】 约瑟夫·阿卜杜勒·瓦希德·曼索尔（Yousif Abdulwahid Mansoor）；

【导师】 张志强；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 尽管混凝土结构的评估已经持续了很长一段时期,积累了大量有价值的技术成果,但是一直没有得到合理的评价方法,尤其是对结构劣化效应科学问题亟待解决。钢筋混凝土是隧道衬砌采用的最广泛的材料之一。从长远来看,混凝土强度是确保隧道衬砌结构长期安全及可靠的最重要参数之一。在隧道耐久性问题中,因赋存环境中氯离子渗透以及碳化作用导致隧道结构出现劣化为常见的,对隧道结构长期安全性和使用性将产生显著地影响。通过肉眼可以观测到的沿着钢筋布置方向裂缝的混凝土破坏,这是由于钢筋横截面积以及钢筋与混凝土之间粘结强度显著降低所造成的。针对此类破坏,已经提出了大量的衬砌劣化模型来预测在有限锈蚀时间条件下隧道衬砌的劣化行为及结果。本论文研究旨在进一步深入探明隧道衬砌劣化效应,特别是对混凝土与钢筋粘结强度以及自身残余强度的影响。通过本文研究,试图建立一套可预测及评价隧道在不同锈蚀程度下其钢筋混凝土衬砌结构强度的方法及流程,也就是研究出不同锈蚀程度下隧道衬砌强度变化规律用以指导隧道衬砌结构设计及为规范修订奠定基础。在试验研究中,主要考虑的影响因素及变量包括：腐蚀速率、腐蚀率、混凝土强度、钢筋直径、混凝土保护层厚度；并且,将腐蚀条件分为3级：轻度腐蚀、中度腐蚀和重度腐蚀,与此对应,采用三种加速腐蚀时间：4天、6天和8天。试验研究共采用120组钢筋混凝土试件,其中48组单轴拉拔试件(150mm×150mm×150mm)和72组压弯试件(1200mm×200mm×300mm)。所有样本均采用珠海眼浪山隧道衬砌所使用的混凝土配合比,48组试件被指定为对比标准试件,没有受到腐蚀；其余72组试件受到外加电流的腐蚀。48组单轴拉拔试件均进行了拉拔试验测试,另外72组压弯试件均进行压弯承载能力测试。对于单轴拉拔试件,通过设计合理的锚固长度以避免屈服失效,从而得到最好的拉拔试验结果。对于压弯试件,通过设计合理偏心距,以实现试件在承受两种作用力(轴向力和力矩)条件下的加载破坏试验。这样设计目的在于模拟出实际隧道衬砌结构的受力条件,通过压弯构件的力学性能试验研究实现对隧道衬砌力学行为的解释。测试者观察在加速腐蚀试验中增加的裂纹全过程,包括加载前、后。整个实验通过对比锈蚀试件与未锈蚀试件在加载测试中所获得试件压缩强度、拉伸强度以粘结强度、位移以及裂缝等指标变化来完成。试验结果表明,试件的锈蚀电流密度(Icorr)与锈蚀时间(T)的乘积,可以被定义为锈蚀因子,它是影响腐蚀试件强度最重要的一个因素。钢筋损失百分数及其强度下降是随着锈蚀因子而增加的。此外,在相同锈蚀因子条件下,不同钢筋直径也会影响钢筋截面损失率,研究发现混凝土保护层厚度对强度损失率有显著影响。锈蚀率与残余强度存在线性相关关系。通过拉拔试验研究得出：在不同锈蚀时间(4天、6天以及8天)情况下,钢筋直径10mm混凝土试件(C30)的粘结强度与其标准试件相比,分别了下降32%,39%以及43%。在极限荷载条件下因腐蚀将会导致钢筋的伸长率以及屈服比降低。这些降低可能导致钢筋在屈服前被过早拉断,对于这种情况不存在普遍关系。极限承载力试验研究表明：不同锈蚀时间下试件最大荷载和最大位移之间有着相似的曲线关系。即,随着锈蚀率增加导致位移增大。在4天锈蚀情况下,试件极限承载力降低了8-13%；6天的锈蚀情况下,试件极限承载力降低12-16%；8天的锈蚀情况下,试件极限承载力降低了24-26%。对于带有单根钢筋的试样而言,第一条裂缝出现在混凝土保护层较薄的一侧,而第二条裂缝或出现在平行于第一条裂缝的一侧或垂直于第一条裂缝,这取决于钢筋的间距以及保护层厚度。对于配有多根钢筋的试件,裂缝出现及扩展或发生在保护层较薄一侧,或者相邻钢筋之间,这取决于相邻钢筋的间距。实测出的引起结构开裂的锈蚀量远远大于理论上沿径向膨胀引起结构开裂的锈蚀量。引起结构开裂的锈蚀估算量可以用原始钢筋截面的百分数来表达,具体可通过劈裂混凝土来量测钢筋直径获得其比率。根据系统大量的试验测试数据,可以采用包括粘结强度、裂缝和试件力学行为来评估腐蚀隧道衬砌的强度。隧道衬砌强度劣化机制依赖于压弯承载试验和拉拔试验。实验结果可以建立许多流程图,它给出了一个设计与评估锈蚀条件下隧道衬砌强度的简单方法,即通过模拟与隧道衬砌受力特性相似的压弯梁试件力学行为来评估因锈蚀引起衬砌强度劣化的方法。基于试验数据的进一步研究,可为规范的实际应用提供一定依据,这些规范可用于评估隧道混凝土衬砌结构腐蚀程度以及新建隧道混凝土衬砌结构的耐久性设计。更多还原

【Abstract】 Recently the world witness, a growing with conception for better assessment of existing concrete structures that have been revealed a need for improved understanding of the structural effects of deterioration. The reinforced concrete is one of the most widely used materials for tunnel lining. In long-term, the strength is one of the most important parameter of the tunnel lining that ensure a safe and reliable service life for tunnels. There are different surrounding environments such as a chloride and carbon penetration, which are common durability problems in tunnels that may have a significant effect on sustainability of reinforced concrete strength. Damage detected visually as coincident cracks along the reinforcement, which are significant result for a reduction of the re-bar, cross-section and loss of bond strength for reinforcement concrete. As a consequence, a number of models that have been developed to predict degradation for tunnel lining due to the corrosion over time are limited. The aim of this study is to deepen an understanding of the tunnel lining effects of deterioration with special attention to the bond strength and residual strength. On the basis of test result, an effort is made to develop a procedure for evaluating the strength of reinforced tunnel lining concrete with corrosion. In the other word; it is trying for developing a procedure to be beginning for publishing standards to evaluate tunnel lining design for corrosion. The experimental variables includes corrosion rate, corrosion duration, concrete strength, rebar diameter and thickness of concrete cover. The corrosion condition have been classified into three levels, light, medium and heavy corrosion, which achieved through applying three acceleration corrosion durations (4,6and8days).A total of120reinforced concrete specimens, which includes48specimens with dimension (150mm×150mm×150mm) and72specimens with dimension (1200mm×200mm×300mm). All specimens are casting by using a concrete mixture for Yelangshan Tunnel at Zhuhai. Out of120specimens,48specimens are chosen as controlled specimen, while the remaining72specimens are chosen as corroded specimens. The48specimens are tested with pullout test, while the72specimens are tested with bending-compression test. The pullout test specimens are designed to get best significant result by provided anchored length and avoid yield failure. The bearing capacity specimens are designed to carry two load forces (axial load and moment) by provided the eccentric distance. The purpose of specimen design is to reflect results for specimen test to be similar for tunnel lining element. The tester is observed the crack growing during the acceleration corrosion, also before and after tests for all specimens. The test method for all specimens is divided into many steps to compare between the corroded and controlled specimen. The main factors for strength are stress (compression and tension), bond strength, specimen displacement and crack.Tests result indicates that the product of corrosion current density (Icorr) with acceleration corrosion duration (T), which is defined as the corrosion index that is a most significant factor effect on the strength of a corroded specimen. The percentage of steel metal loss and the reduction of strength are increasing with increasing corrosion index. Moreover, the diameter of steel bar is affected on the extent of metal loss at constant corrosion index. The effect of concrete cover thickness on the loss strength is significant. There are a linear relationship between corrosion rate and residual strength. The pullout test result found that there is32%,39%and43%reduction with bond strength for concrete strength (C30) and bar diameter10for4,6and8day corrosion constantly comparison with the controlled specimen. Corrosion may reduce both the elongation and the ratio of yield to ultimate strength of the reinforcement at maximum load. This reduction leads to premature fracture of the bar before reaching to ultimate yield strength. There are no general relationships for this situation.The bending-compression test result found that the relationship between the maximum load and displacement has same curve shape for all duration. Also, there are increasing in the displacement with increases corrosion rate. The percentage of losing load for specimen is8-13%for4days corrosion,12-16%for6day corrosion and24-26%for8days corrosion.Cracks are propagating first in the direction of the smaller concrete cover for single bars. The second crack propagates to the same face or normal to the first crack depending on bar spacing and relative cover sizes. For multiple bars the cracks propagate first in the direction of the smaller cover that is depending on the spacing between adjacent bars and the relative bars size. The actual amount of corrosion is substantially greater than the amount of theoretical radial expansion. An estimate of the amount corrosion express as a percentage of the original bar area.Based on the theoretical and experimental results, the evaluation procedure includes three significant steps:bond strength, crack and specimen performance. The mechanism for tunnel lining strength is depended on the experimental tests, bending-compression test and pullout test. The results found many flow charts that give a simple method to design and evaluate the tunnel lining strength for corrosion by designing specimen with similar tunnel lining condition.With validation against further test data the procedures, which is developed in this study could be a form the basis for specification of practice for the assessment of corrosion-damaged concrete tunnel lining structures and the durability design of new concrete tunnel lining structures.更多还原