高压岔管首次充排水衬砌开裂规律与渗透特征

高压岔管首次充排水过程是影响衬砌裂缝产生和扩展规律、渗透规律以及长期受力特性的关键因素,亦是关乎结构安全与围岩稳定的重要工况。以阳江抽水蓄能电站钢筋混凝土高压岔管为工程背景,基于流固耦合方法,采用离散单元法(PFC~(2D))研究了首次充水裂缝开展位置与初始地应力的关系;然后,利用有限差分法(FLAC~(3D))分析了衬砌起裂过程和贯通临界压力,明确了首次充排水至平衡状态的衬砌渗透特性以及梯级排水条件下衬砌稳定性;最后,研究了钢筋和锚杆对衬砌结构力学特性的影响,并提出限裂设计参数优化方案。结果表明:内水压力2.8 MPa为衬砌起裂临界压力,继续增至4 MPa时衬砌结构裂缝贯通;裂缝是高压岔管充水期内水外渗和放空期外水压消散的重要渗流通道,衬砌结构配筋与锚杆支护是限制裂缝开度的关键措施;放空期高外水荷载作用下衬砌存在受压破坏风险,应对内水放空梯度进行严格控制。

Study on cracking law and permeability characteristics of high pressure bifurcated pipe lining during first filling and emptying

The first filling and emptying process of high-pressure bifurcated pipe is the key factor affecting the generation and expansion of lining cracks, permeability law and long-term stress characteristics. It is also an important condition related to structural safety and surrounding rock stability. Taking the reinforced concrete high pressure bifurcated pipe of Yangjiang Pumped Storage Power Station as the engineering background, based on the fluid-solid coupling method, the relationship between crack location and initial geostress in the first filling are studied by using the discrete element method (PFC2D). The lining cracking process and the critical penetration pressure are analyzed by using the finite difference method (FLAC3D). The permeability characteristics of the lining under equilibrium state of the first filling and emptying and the the lining stability under the stepped drainage condition are studied. The influence of reinforcement and anchor bars on the mechanical characteristics of the lining structure is studied, and the optimization scheme of crack-limiting design parameters is proposed. The results show that 2.8 MPa is the critical internal water pressure for lining cracking, and the cracks penetrate lining when the internal water pressure increased to 4 MPa; the cracks were the important seepage channels for outward flowing in filling stage and external water pressure dispersion in emptying stage ; the lining structure reinforcement bar and anchor rod support are the key measures to limit the crack opening; the lining has risk of compression damage under high external water load, so the internal water release gradient should be strictly controlled.