隧道二次衬砌混凝土的抗裂性能研究

发布时间：2018-05-22 20:39

本文选题：隧道二次衬砌 + 配合比设计参数　；参考：《长安大学》2014年硕士论文

【摘要】：隧道二次衬砌混凝土的开裂不仅降低隧道的安全质量及耐久性，而且影响隧道的施工与应用环境。目前，实际工程中的二次衬砌混凝土强调强度等级与工作性能等基本要求，忽略了对长期抗裂性能的研究。为了提高二次衬砌混凝土的抗裂性能，应对其影响因素进行分析，选择确定合理配合比、研制抗裂复合材料，改善二次衬砌混凝土的抗裂性能。本文对传统的圆环约束法进行了改进，同时选择收缩形变、弹性模量与劈裂抗拉强度作为评价指标，进而从体积变形与力学性能的角度进行综合的分析，准确地表征出混凝土的抗裂性能。结果表明：采用改进后的圆环法测试混凝土的开裂时间，试验周期得以缩短，可靠性得到提高；抗裂系数与圆环法测出的结果具有较强的相关性，可用来表征混凝土的抗裂性能。从二次衬砌混凝土原材料与施工要求出发，研究了配合比设计参数、常用外加剂及掺合料对混凝土抗裂性能的影响。研究结果表明：配合比设计参数中，水灰比与胶凝材料总量对混凝土抗裂性能的影响较强，骨料最大粒径与砂率的影响程度较弱；水灰比过高与过低都会对混凝土早期抗裂性能产生不利影响，胶凝材料总量的增加会增大混凝土的开裂敏感性；粉煤灰等量代替水泥掺入混凝土时，随着掺量的增加，混凝土抗裂性能得到提高，但掺量较高时，提高程度增幅减缓；膨胀剂与减缩剂均可以对混凝土的收缩变形产生抑制作用，当两者分别以内掺与外掺的方式掺入混凝土时，可以提高混凝土的抗裂性能，且随着掺量增加，提高作用不断加强；减水剂在合理范围内对抗裂性能有一定的减弱作用，但影响幅度较小。在影响因素的研究分析基础上，选择粉煤灰、膨胀剂与减缩剂作为抗裂材料进行组成设计与抗裂性能研究。结果表明：通过正交设计方法，确定粉煤灰、膨胀剂与减缩剂的掺配比例为20%：8%：1.5%时，，复配材料的抗裂性能最好；将复配的抗裂材料与市售的复合抗裂外加剂对比分析，结果显示各项性能均优于后者。
[Abstract]:The cracking of the secondary lining concrete not only reduces the safety quality and durability of the tunnel, but also affects the construction and application environment of the tunnel. At present, the secondary lining concrete in practical engineering emphasizes the basic requirements of strength grade and working performance, and neglects the study of long-term crack resistance. In order to improve the crack resistance of the secondary lining concrete, the influencing factors should be analyzed, the reasonable mix ratio should be determined, the crack resistant composite material should be developed, and the crack resistance performance of the secondary lining concrete should be improved. In this paper, the traditional circumferential constraint method is improved, and the shrinkage deformation, elastic modulus and splitting tensile strength are selected as the evaluation indexes, and then the volume deformation and mechanical properties are comprehensively analyzed from the point of view of volume deformation and mechanical properties. The crack resistance of concrete is accurately characterized. The results show that the test period is shortened and the reliability is improved by using the improved ring method, and the crack resistance coefficient has a strong correlation with the results obtained by the ring method. It can be used to characterize the crack resistance of concrete. Based on the raw materials and construction requirements of secondary lining concrete, the effects of mix ratio design parameters, common admixtures and admixtures on the crack resistance of concrete are studied. The results show that the influence of water-cement ratio and total amount of cementing material on the crack resistance of concrete is stronger than that of the maximum particle size and sand ratio of aggregate. Too high water-cement ratio and too low water-cement ratio will have adverse effects on the early crack resistance of concrete, and the increase of aggregate amount of cementitious material will increase the cracking sensitivity of concrete. The crack resistance of concrete is improved, but when the content of concrete is high, the increase of increasing degree is slowed down, the expansion agent and shrinkage reducing agent can inhibit the shrinkage and deformation of concrete, when the concrete is mixed in and out of the concrete respectively, It can improve the crack resistance of concrete, and with the increase of the content of concrete, the improvement effect is strengthened, and the water-reducing agent has a certain weakening effect in a reasonable range, but the effect is small. On the basis of research and analysis of influencing factors, fly ash, expansion agent and shrinkage reducer were selected as crack resistant materials to design composition and crack resistance. The results show that when the proportion of fly ash, expansion agent and shrinkage reducer is 20: 8: 1.5%, the anti-crack performance of the composite material is the best by orthogonal design. The results show that each performance is superior to the latter.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.91;U454

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