近些年来除传统的陆路交通之外，我国涌现出越来越多的水下交通运输系统，建成了一批技术复杂、设计及施工难度大、科技含量极高的长大沉管隧道，其中最具有代表性的为连接香港-珠海-澳门的港珠澳隧道工程。与此同时，我国处于环太平洋地震带与欧亚地震带之间，大部分地区需要采取抗震设防措施。因此，在地震动作用下沉管隧道结构的安全性问题也越来越受到社会各界广泛的关注和重视。沉管隧道结构接头剪力键作为沉管隧道结构中的主要抗震受力构件，因此其抗震性能需要重点关注。本文研发了一种新型混杂纤维增强混凝土材料，系统研究了混杂纤维增强混凝土剪力键及沉管隧道的抗震性能。主要工作研究和创新成果如下： (1)基于混杂纤维混凝土材料性能试验，研究了素混凝土、钢-聚丙烯-玄武岩纤维混凝土、钢-玄武岩纤维混凝土和钢-聚丙烯纤维混凝土在拉、压、弯、剪方面的力学性能，得到了纤维混凝土材料的立方体抗压强度、棱柱体轴心抗压强度、“哑铃型”试件轴心抗拉强度、劈裂抗拉强度、剪切强度和弯曲强度。除此之外，得到了混杂纤维混凝土材料承受轴心受压荷载和轴心受拉荷载时的应力-应变曲线、双面剪切荷载作用下的荷载-位移曲线及四点弯曲荷载作用下的荷载-位移曲线。通过对混杂纤维混凝土材料在受压、受拉、抗剪切及抗弯曲等方面的参数分析，得到了混杂纤维混凝土材料在最高强度、最佳韧性及最优综合性能方面的材料配比。掺入混杂纤维之后，与素混凝土试件相比，棱柱体轴心抗压强度和受压韧性分别提高了8.5％～16.5％和18％～24％；轴心抗拉强度和轴心抗拉韧性分别提高了64.1％～87.4％和108.3％～200％；剪切强度和剪切韧性分别提高了70.9％～116.4％和791.2％～1041.2％；弯曲强度和弯曲韧性分别提高了13.6％～42.2％和314.3％～551.4％。 (2)基于混杂纤维混凝土材料的最优配比，分别进行了普通钢筋混凝土和混杂纤维增强钢筋混凝土剪力键构件的抗震性能试验。分析了剪力键在低周往复位移荷载作用下的破坏过程、破坏特征、承载能力、滞回特性、变形能力、耗能能力、损伤演化、刚度退化、混凝土表面裂缝开展规律、钢筋应变及混凝土应变等抗震性能指标。揭示了在不同混凝土标号、不同钢筋配筋率及不同纤维体积掺量下的剪力键抗震性能变化规律。掺加有180㎏／m³钢纤维及4.5㎏／m³玄武岩纤维的剪力键构件相比于普通混凝土剪力键构件在极限承载能力、耗能能力和延性方面分别提高了44.6％、229％和53.1％。 (3)采用ABAQUS有限元软件，利用混杂纤维混凝土材料试验得到的钢-玄武岩纤维混凝土材料的轴心受压及轴心受拉应力-应变曲线，建立了钢-玄武岩纤维混凝土材料的应变-损伤关系，并对纤维混凝土双面剪切试验进行了有限元模拟。在双面剪切试验有限元模拟的基础上，采用钢-玄武岩纤维混凝土材料对剪力键构件抗震性能试验进行了有限元的模拟与分析。根据剪力键构件的材料力学性能试验，回归得到了钢-玄武岩纤维混凝土轴心抗压强度增强因子及轴心抗拉强度增强因子与纤维体积掺量的关系。根据剪力键构件抗震性能试验结果，回归得到了剪力键的抗剪极限承载力计算公式。由公式计算得到的剪力键极限承载力与试验结果相比，最大误差为13％，最小误差为1％。 (4)建立了三维土体-沉管隧道结构有限元模型，采用粘弹性人工边界，并通过等效节点应力时程的方法实现了地震动在土体结构中的入射。在沉管隧道结构管节间接头处采用钢-玄武岩纤维增强钢筋混凝土材料对沉管隧道整体结构在地震动下的动力响应进行了有限元分析，并将得到的结果同普通钢筋混凝土沉管隧道整体结构在地震动下的动力响应结果进行了比较。通过沉管隧道整体结构的变形、管节截面损伤分布、沉管隧道管节间接头变形情况、水平剪力键及竖向剪力键的变形情况等结果，讨论了接头处采用纤维混凝土材料的沉管隧道结构及整体采用普通混凝土材料沉管隧道结构在地震动下的响应差异。模拟结果表明，相比较于接头部位采用普通混凝土材料的沉管隧道结构，接头部位采用混杂纤维混凝土材料的沉管隧道结构整体变形值减小25％～30％，管节间接头变形值减小20％～30％，剪力键变形值减小30％～40％。 关键词：抗震性能；剪力键；沉管隧道；混杂纤维混凝土材料；钢纤维；玄武岩纤维；聚丙烯纤维。
In recent years, more and more transportation system underseas were constructed except the traditional transportation. A large scale of immersed tunnels with complex construction technology, difficult design and high scientific content were constructed, the most typical immersed tunnel among those was the immersed tunnel that connected Hong Kong-Zhuhai-Macao. Meanwhile, China located between the Eurasia seismic belt and the circum-pacific seismic belt. Therefore, the structures and buildings in most areas of China need to be designed with earthquake resistance protections. Thus, the security problems of the immersed tunnel under seismic loads are becoming more and more important. The seismic behaviour of concrete shear keys in the immersed tunnel joints that resist the seismic loading need to be focused on. This study develops a new type of hybrid fibre reinforced concrete (HFRC) material. The seismic behaviour of hybrid fibre reinforced concrete shear keys and immersed tunnel was systematically studied. The primarily works and conclusions were summarized as follows: (1)Based on the material tests of hybrid fibres reinforced concrete, the mechanical properties including uniaxial compression, uniaxial tension, flexure and shear of plain concrete, steel-basalt-polypropylene HFRC, steel-basalt HFRC and steel-polypropylene HFRC were studied. The compression strength of cubic, the uniaxial compression strength of prism, the uniaxial tensile strength, splitting tensile strength, shear strength and flexure strength were obtained from the material tests. Besides, the stress-strain curves of uniaxial compression and uniaxial tension, the load-displacement curves under four points flexure and direct shear were obtained from the tests. Through the parametric analysis of the HFRC under compression, tension, direct shear and flexure, the specific composites of HFRC with the highest strength, best toughness and optimal mechanical properties were obtained. Comparing the strength and toughness of HFRC with plain concrete, the uniaxial compress strength and toughness were improved 8.5%～16.5% and 18%～24%, respectively; the uniaxial tensile strength and toughness were improved 64.1%～87.4% and 108.3%～200%, respectively; the shear strength and toughness were improved 70.9%～116.4% and 791.2%～1041.2%, respectively; the flexure strength and toughness were improved 13.6%～42.2% and 314.3%～551.4%, respectively. (2)Based on the optimized composites of HFRC, the seismic behaviour of normal concrete shear keys and HFRC shear keys under cyclic loading were tested. The seismic behaviour indexes that consisted of failure process, failure characteristics, carrying capacity, hysteretic characteristics, deformation behaviour, energy dissipation capacity, damage evolution, stiffness degradation, cracks spreading on the concrete surface, the strain of the concrete and the strain of steel bar were analyzed. Meanwhile, the contributions of different concrete grades, different reinforcement ratios and different volume fractions of fibres to the seismic behaviour of shear keys were revealed. Adding 180 ㎏/m³ steel fibres and 4.5 ㎏/m³ basalt fibre to HFRC improved the ultimate load-carrying capacity, energy dissipation ability, and ductility of shear keys by 44.6 %, 229 %, and 53.1 %, respectively. (3)The finite element software ABAQUS was adopted to simulate the tests. The strain-damage relationship of steel-basalt HFRC was established according to the uniaxial compression and uniaxial tension stress-strain curves. Subsequently, the direct shear test of material tests was simulated by ABAQUS. Based on the simulation of direct shear test, the seismic behaviour tests of concrete shear keys were simulated and analyzed by ABAQUS. The relationships of uniaxial compressive enhancement factor versus volume fraction of fibres and uniaxial tensile enhancement factor versus volume fraction of fibres were regressed based on the results of material tests for the shear keys. Meanwhile, the formula to calculate the ultimate shear resistance of the shear keys was regressed based on the hysteretic tests results of the concrete shear keys. The maximum error and the minimum error of the formula to calculate the ultimate shear resistance were 13% and 1%, respectively. (4)A three-dimensional finite element model of the soil-immersed tunnel structure was established in ABAQUS, and the viscoelastic artificial boundary was adopted to simulate the actual soil boundary. Besides, the oblique incidence of the seismic loading was realized by the equivalent nodes stress time-history method. The seismic behaviour of the immersed tunnel joint between segments with steel-basalt hybrid fibre reinforced concrete were compared with the immersed tunnel with normal concrete. The difference between the seismic response of immersed tunnel with hybrid fibre joints and immersed tunnel with normal concrete were studied through the analysis of the deformation for the immersed tunnel, the damage of the segment element, the variation laws of the deformation for the roof-floor plate of the immersed tunnel and the behaviour of the shear keys in the immersed tunnel joints. Comparing the simulation results of HFRC immersed tunnel joints with plain concrete immersed tunnel joints, the deformation of the whole structure decreased 25%～30%, the deformation of the joints decreased 20%～30%, the deformation of the shear keys decreased 30%～40%. KEY WORDS: seisimic behaviour; shear key; immersed tunnel; hybrid fibres reinforced concrete material; steel fibre; basalt fibre; polypropylene fibre.