【作者】 祝云华；

【导师】 刘新荣；

【作者基本信息】 重庆大学 ， 岩土工程， 2009， 博士

【摘要】 喷射混凝土技术,已成为地下工程和岩土工程支护中最有效的支护手段之一,它不仅可以作为初期支护确保隧道施工过程中的安全,也可以与其它支护构件或配合或单独地作为结构物的永久支护,维护结构物的长期稳定和安全使用。近年来,为了适应不同的围岩条件和施工方法,出现了许多新型的喷混凝土,如高强度喷混凝土、纤维喷混凝土、聚酯喷混凝土等,其中钢纤维喷射混凝土,因工程力学性能在很多方面都优于普通喷射混凝土,越来越受到工程界的重视,并在隧道及地下工程的衬砌支护中得以应用,但一直以来对其力学特性及隧道单层衬砌相关问题的研究还不够深入。本文结合国家自然科学基金重点项目(50334060)和国家自然科学基金创新群体基金(50621403),在前人研究的基础上,通过理论分析、试验研究、数值模拟和现场测试等方法,对钢纤维喷射混凝土的力学特性及其在隧道单层衬砌中的应用进行了较为系统和深入的研究。主要研究工作及成果如下:①研究了钢纤维对混凝土的增强机理。根据钢纤维喷混凝土应力-应变曲线实验的基本特性,将钢纤维喷混凝土的破坏演化过程分成四个相互联系又各具特点的阶段;通过对钢纤维喷混凝土梁的抗弯机理分析,推导出了裂后弯矩与极限弯矩的关系表达式;并从复合材料力学和断裂力学的观点阐述了钢纤维对混凝土的增强、增韧作用。②研究了钢纤维喷混凝土的抗压强度、抗拉强度、早期强度、粘结强度以及抗渗性能等基本力学特性,掌握了不同类别钢纤维喷混凝土的力学性能与掺量关系,确定了纤维的合理掺量,并提出了适合于隧道单层衬砌的钢纤维喷射混凝土力学特性控制指标。③通过钢纤维喷混凝土的荷载-挠度试验,对其弯曲韧性进行了计算分析,研究了弯曲韧性指标随纤维掺量的变化规律,结合试验结果,对钢纤维喷混凝土韧性指标的相关性进行了探讨;根据立方体切片实验,分析了钢纤维在喷射混凝土中的分布规律,并将实验结果与理论计算进行对比,得到了纤维在喷射混凝土中服从球面上的Fisher分布。④从分析单层衬砌的支护对象入手,对隧道喷混凝土单层衬砌的力学机理进行了研究。单层衬砌在荷载经历过程中表现出两种不同的力学传递:一种是从影响支护应力状态的围岩向外部传递,另一种是应力内部的传递;喷混凝土支护的受力机理分为两类:局部受力和整体受力;对锚杆在喷混凝土单层衬砌中的支护作用进行了分析。⑤通过对隧道围岩稳定性的影响因素分析,从突变理论入手,研究了隧道单层衬砌顶部复合结构的稳定性。采用平直梁简化力学模型,建立了隧道单层衬砌支护-围岩复合体拱顶失稳的尖点突变模型,导出了其失稳的充要力学条件判据和系统失稳时拱顶变形突跳量及能量释放的表达式,讨论了受力状况变化对拱顶复合结构稳定性的影响。⑥采用有限元法对钢纤维喷射混凝土单层衬砌进行了数值模拟,分析了隧道围岩-支护结构体系的位移场、应力场、塑性区以及支护内力的分布规律和变化特性,探讨了不同围岩级别下隧道开挖后的围岩稳定性,获得了钢纤维喷射混凝土单层衬砌的合理喷层厚度,并基于现场监测成果对隧道单层衬砌支护结构进行了稳定性评价。⑦以摩天岭隧道通风斜井为依托工程,按照挪威隧道工法的原理和技术要求,从施工工艺、结构设计、关键技术、经济性及防排水等方面系统地研究了湿喷钢纤维混凝土在隧道单层衬砌中的应用,初步形成具有质量检验及评定标准的隧道单层衬砌施工技术。更多还原

【Abstract】 The shotcrete technology has become one of the most effective means of supporting in underground engineering and geotechnical engineering; it not only can be the initial period supports which insures construction security of tunnel, but also take the structure permanent supports and protections along with supports and protections component, and maintain structure long-term stability and safety handling. In recent years, in order to adapt to the different surrounding rock condition and construction method, it appears many new kinds of shotcrete, such as high strength shotcrete, fiber shotcrete, and polyester high strength shotcrete, and so on. Speaking of the engineering mechanics performance, the steel fiber reinforced shotcrete has surpasseed ordinary shotcrete in many aspects, thus it is given more and more attention by engineering area, which is applied widely in tunnels and underground engineering, but its mechanical characteristics and related issues have been always falling behind application. Combined with the key project of the National Natural Science Foundation and National Natural Sciences Foundation Innovation Community Fund, on the basis of previous research, the mechanical characteristics of steel fiber reinforced shotcrete and action mechanism of single layer tunnel lining is systemic and thoroughly researched by theory analysis, experimental test, numerical simulation and field test. The main works and achievement of thesis can be drawn as follows:(1) The reinforced mechanism of steel fiber reinforced concrete is studied. According to the leading features of stress-strain curve, the growing of damage in steel fiber reinforced concrete is subdivided into four stages with mutual connections and characteristic stage. According to flexural mechanism analysis of steel fiber reinforced shotcrete beam, relations expression between moment capacity and cracking moment is obtained. The reinforcing and toughening mechanism of steel fiber to contrete is set forth in details from the point of view of composite material mechanics and fracture mechanics.(2) The compression strength, tensile strength, initial strength, cohesional strength and impermeability properties of steel fiber reinforced shotcrete are key researched; among basic mechanical experiments, the relationship between mechanical properties and content of different steel fiber reinforced shotcrete is grasped; a reasonable content of fiber is determined, and the mechanical proper guideposts of shotcrete used for single layer lining are presented.(3) With load and deflection test of steel fiber reinforced shotcrete, its flexural toughness is calculated and analyzed, the change pattern of curving toughness index along with the fiber contents is studied, combined with test results, the relevance of toughness index of steel fiber reinforced shotcrete is discussed. Through cube slice experiment, the distribution of steel fiber in shotcrete is obtained, and experimental results and theoretical calculation is comparative analyzed, slice test of steel fiber reinforced shotcrete proves steel fiber obeys Fisher distribution of spherical surface among shotcrete.(4) Starting with analysis of support object of single layer lining, the mechanical mechanism mechanism of single layer tunnel lining is studied; it shows two different mechanical transfer mechanisms in the load course: one is rock stress transfers to the outside, and the other is the internal stress transfers. Supporting mechanism of shotcrete is divided into two categories: the part stress and the whole one. And the mechanism of anchors for single layer tunnel lining by shotcrete is analyzed too.(5) By analyzing the impact factors of stability of tunnel surrounding rock, based on cusp catastrophe theory, the stability of composite structure from top of single layer tunnel lining is studied. Adopted simplified mechanical model of straight beam, the catastrophe model of vault complex of single layer tunnel lining and surrounding rock is set up, and necessary and sufficient conditions for instability and vault deformation at system instability as well as expression which energy releases are obtained, and thesis discusses the influence between vault complex stability and changing force on structure.(6) Using finite element method, the stability of single layer tunnel lining by steel fiber reinforced shotcrete is numerical simulation analyzed; the surrounding of tunnel rock and support system structure, displacement field, stress field, plastic zone as well as internal forces changes of support characteristics are obtained; the stability of different surrounding rock grade of tunnel excavation is studied, and reasonable spray layer thickness of single layer tunnel lining by steel fiber reinforced shotcrete is obtained. Simultaneity, the supporting effect of single layer lining by steel fiber reinforced shotcrete is also analyzed and evaluated by in-situ monitoring results.(7) With a project of inclined shaft of Motianling tunnel, based on the principles and technical demands of New Austrian Tunneling Method, the application of single layer tunnel lining by steel fiber reinforced shotcrete with wet-mix method is studied systematically by construction technology, structural design, key technology, economic analysis and waterproof and drainage, and a set of quality inspection and evaluation standards of construction technology for single layer tunnel lining is initial formed.更多还原