抽水蓄能电站蜗壳组合结构中粘-滑循环接触带的传力行为

Steel spiral cases in pumped storage hydroelectric power plants (HPPs) are in general filled with water and temporarily pressurized while encasement concrete is placed. A steel spiral case in a pumped storage HPP should bear cyclic internal water pressure (IWP). The separation zones between the steel spiral case and its surrounding concrete are thus in continuous evolution, and so are the in-contact zones. The term “cyclic-stick-to-slip contact zones” has come to be used to refer to the evolving regions at the borders of the separation and in-contact zones. This cyclic contact behaviour can play an important role in addressing the issue of low-cycle fatigue of steel spiral cases. The main challenge faced by steel spiral cases in pumped storage HPPs is high frequency and amplitude of cyclic static IWP. Both model tests and finite element simulation will be performed in this research. The purpose of this research is to explore (1) cyclic contact behaviour in spiral case structures (SCSs), (2) load-transferring mechanism in cyclic-stick-to-slip contact zones and (3) its effect on stress spectra of steel spiral cases. Both acoustic emission and contact electrical resistance measurement techniques will be used to monitor the contact status between the steel liners and the concrete in the model tests. The two techniques are particularly useful in monitoring various contact behaviour in steel-concrete composite structures. In order to investigate unevenly distributed gaps in SCSs, pre-pressurization during construction will be taken into account in the numerical modelling. In an attempt to consider uneven contact surfaces in SCSs, higher-order solid elements will be employed to describe steel liners. This research will provide a framework for fatigue-life prediction and fatigue design of steel spiral cases in pumped storage HPPs. In addition, this research will serve as a base for future studies concerning fatigue mechanics of penstocks in HPPs.

抽水蓄能机组蜗壳通常采用充水保压技术埋入混凝土，在内水压力频繁的加-卸载作用下，钢蜗壳-混凝土间的脱空区和过盈接触区会交替转化，两种区域的交界附近随之出现可变的粘-滑循环接触带，其中的循环接触传力现象可能与钢蜗壳潜在的低周疲劳过程有密切的力学关联。本项目拟针对抽水蓄能机组蜗壳频繁承受较高幅值静水荷载循环的受力特点，开展物理试验和数值模拟研究，澄清组合结构中的循环接触力学现象，阐明循环接触带的传力行为及其与钢蜗壳应力谱的力学联系。物理试验拟采用声发射和接触电阻测试技术同步捕捉钢衬-混凝土间接触状态的细微变化，以克服接触面上的各种力学行为难于捕获、监测的问题；数值建模拟考虑充水保压施工过程，并采用高阶实体单元描述钢衬，模拟聚焦于初始保压间隙的“非均匀”及接触面的“非平滑”特点。研究成果可以为抽水蓄能机组蜗壳的疲劳寿命预测及抗疲劳设计提供科学依据，推进水电站流道系统疲劳力学研究的发展。

近年来我国抽水蓄能建设大幅提速，截至目前我国抽水蓄能电站装机容量已居世界第一。抽水蓄能电站的一个重要特点是其流道结构需承受较高循环频率、较大循环幅值的内水压力作用。根据通常对钢材遭受疲劳破坏的规律认识，抽水蓄能电站的引水钢结构系统在服役期内会面临一定程度的低周疲劳问题。抽水蓄能机组蜗壳通常采用充水保压技术埋入混凝土，钢蜗壳-混凝土间接触状态随内水压力加-卸载的演化过程异常复杂，在此过程中，钢蜗壳和混凝土之间在循环接触区域的传力行为表现出高度非线性，应力状态循环变化，应力谱复杂。本项目以充水保压蜗壳结构为对象，针对其频繁承受较高幅值静水荷载循环的受力特点，研究聚焦于钢蜗壳-混凝土间的粘-滑循环接触行为，探索循环接触带的传力行为及其与钢蜗壳应力谱的力学联系，围绕充水保压蜗壳组合结构中的接触传力及与其相关的钢蜗壳疲劳问题，开展了相关的计算方法研究及其验证工作，并将方法应用于实际工程算例，进一步研究了钢蜗壳与混凝土之间保压间隙的演变机理及其影响因素、钢蜗壳与混凝土间的接触传力机制及钢蜗壳的疲劳问题。相关研究成果能够为钢蜗壳的疲劳寿命预测及抗疲劳设计提供科学依据。