海底隧道纤维混凝土力学性能发展研究

Research on the Development of Mechanical Properties of Fiber Reinforced Concrete in Channel Tunnel

研究目的:海底大直径隧道管片结构对混凝土的抗裂性提出了较高的要求,采用纤维混凝土能够有效解决这一问题。本文对纤维混凝土在不同养护龄期下的抗压强度以及弹性模量进行试验研究,分析不同聚丙烯纤维及钢纤维掺量对混凝土抗压强度以及弹性模量随龄期发展的影响规律,研究纤维掺量对混凝土力学性能的影响,并利用扫描电镜对聚丙烯纤维混凝土进行观测,从微观角度分析纤维与混凝土的作用机理。研究结论:(1)钢纤维对混凝土强度有提高作用,2%钢纤维掺量的混凝土试件抗压强度要明显高于其他组的试验结果,纤维混凝土的强度离散性高于普通混凝土;(2)纤维可明显提高混凝土的弹性模量,2%钢纤维掺量的混凝土试件弹性模量最高,2 kg聚丙烯纤维掺量的混凝土28 d弹性模量较3 d提升幅度最大;(3)微观试验表明,聚丙烯纤维表面较为光滑,与混凝土基体结合性能较差,是聚丙烯纤维混凝土强度较低的原因之一;(4)本研究成果可为海底隧道混凝土管片设计提供指导。

Research purposes:The submarine large diameter tunnel segment structure has a high demand on the crack resistance of concrete.Adding fiber into concrete can solve this problem effectively.In this paper,the compressive strength and elastic modulus of fiber concrete at different curing ages were tested.The influences of different content of polypropylene fiber and steel fiber on the axial compressive strength and elastic modulus of concrete with the development of age were analyzed,and the impact of fiber content on the dispersion of concrete mechanical properties was studied.In addition,the microstructure of the polypropylene fiber concrete was observed by scanning electron microscope and the mechanism of action between fiber and concrete was analyzed.Research conclusions:(1)Steel fiber can improve the compressive strength of concrete.The compressive strength of concrete with 2%steel fiber content is significantly higher than the test results of other groups.The dispersion of strength of fiber concrete is higher than that of ordinary concrete.(2)The elastic modulus of concrete can be significantly increased by adding fiber.The elastic modulus of concrete with the content of 2%steel fiber is the maximum and the elastic modulus of concrete with the content of 2 kg polypropylene fiber at 28 days increases the most than that of 3 days.(3)The microcosmic test shows that the polypropylene fiber has a smooth surface and poor bonding performance with concrete matrix,which is one of the reasons for the low strength of polypropylene fiber concrete.(4)The research results can provide guidance for the design of concrete pipe segments of the channel tunnel.