人工冻土与混凝土结构相互作用接触面变形机理与本构模型研究

When constructing the large-scale urban underground projects(e.g. Subway Cross-passage, Shields' Launching and Arriving) , using freezing method to build the mine borehole and building the structures on permafrost, the deformation mechanism and constitutive model of the interface between frozen soil and structure are the key mechanic problems. The related research is rarely reported at home and abroad. This subject intends to develop a large-scale shear test instrument which can investigate interface interaction between artificial frozen soil and the structures. Based on laboratory experiments, the relationship of shear stress and strain of the interface between artificial frozen soil and different structures(Concrete structures are mainly characterized by different roughness) will be researched at different conditions,including different soil(clay and sand), different frozen soil interface temperature, different interface pressure, different structure surface roughness, different rate of shear and so on. The mechanical characteristics of the interface between artificial frozen soil and Concrete structures will be analysed. The variation of mechanical behavior between artificial frozen soil and structures will be revealed. Based on damage mechanics, by introduing damage factors and considering the influence of temperature, interface pressure and surface roughness of the structure, the damage constitutive model for the interface between artificial frozen soil and the structures will be proposed, followed by the explanation of the microscopic mechanism. Finally, the study will provide the scientific basis and parameters in terms of design of the concrete structures of cross-passage using artificial freezing method, the reinforcement at shiled shaft using horizontal freezing method and the pile foundation in permafrost regions.And the theory of frozen soil mechanics will be enriched.

大规模城市地下工程（如地铁联络通道、盾构进出洞）及矿山井筒利用冻结法施工和多年冻土上修造建筑物构筑物，面临着冻土与结构接触面变形机理与本构模型的关键力学问题。目前国内外鲜有其研究报道，本课题拟自行研制大型人工冻土与结构接触面相互作用的剪切实验仪，通过室内试验，研究不同土质（粘土和砂土两种土）、冻土界面温度、接触面压力、结构表面粗糙度等条件下，人工冻土与混凝土结构接触面（混凝土结构主要以不同粗糙度表征）剪应力一位移关系，分析人工冻土与混凝土结构接触面界面层中力学特性，揭示人工冻土与混凝土结构接触面力学行为的变化规律，引入损伤因子，基于损伤力学建立考虑温度、接触面压力（法向应力）、结构表面粗糙度的人工冻土与混凝土结构接触面损伤本构模型，并进行机理解释。为解决人工冻结施工联络通道混凝土结构设计、水平冻结端头加固冻结设计及多年冻土区桩基设计等提供科学依据和参数，并丰富冻土力学理论。

大规模隧道工程及矿山井筒利用冻结法施工和多年冻土区修造建构筑物，面临冻土与结构接触面的关键力学问题。自行研制大型人工冻土与结构接触面剪切实验仪，研究不同土质、接触面温度、压力、粗糙度等条件下，人工冻土与结构接触面剪应力一位移关系、力学行为、接触面界面层中力学特性，揭示人工冻土与结构接触面力学行为的变化规律；建立人工冻土与结构接触面损伤本构模型。为解决人工冻结及多年冻土区桩基设计等提供科学依据和参数，并丰富冻土力学理论。.研制了大型多功能冻土-结构接触面循环直剪系统DDJ—1，该系统能实现0～-20℃接触面温度，多种粗糙度的钢板模拟混凝土结构、施加四种法向边界条件，可观测接触带土体内部剪切位移，实现循环和单调两种剪切形式。.研究表明，在第一循环初始阶段均会产生一个由冻结力和滑动摩擦共同形成的剪应力最大值τmax，即极限冻结强度，剪切滑移破坏后的峰后剪切应力，即残余冻结强度；极限冻结强度与冻土温度成线性关系，残余冻结强度随温度变化呈现三种典型规律；冻结强度均随法向应力及粗糙度增大而增大，极限冻结强度与法向应力关系符合摩尔库伦定律，提出了极限冻结强度与粗糙度、冻结温度、法向应力的经验公式；给出了循环剪切中法向应力、法向位移、最大剪应力、剪切循环之间的关系，揭示了接触面循环剪切时剪应力与剪位移和法向位移的变化规律；同一剪切循环内，存在接触面剪应力和相对法向位移异向性，该异向性随粗糙度增大而呈衰减性增加，随循环次数增加而减小，接触面异向性发挥程度与初次剪切方向和冻土特性有关。.不同粗糙度结构接触界面层变形特性基本相似，冻土颗粒的剪切位移随法向应力增大而增大，随冻土深度增大而减小，试验条件范围内接触界面层厚度为0.5～3.5mm。.采用损伤力学理论，选择不可逆性体应变与最大不可逆性体应变的比值作为损伤因子，建立了用于描述冻土与结构接触面剪切行为的抗剪强度与压缩体应变损伤模型。