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坝基的渗流动态,很大程度上受控于坝基帷幕体的完好程度和止水效果,但是由于地下水长期存在的物理–化学作用,造成帷幕体防渗性能的衰减。为了能够再现坝基帷幕体防渗性能衰减的过程,依据渗流水力学以及水文地球化学的基本理论,建立了反映帷幕体防渗时效的多场耦合作用模型。该模型由渗流模块、溶质迁移模块、地球化学模块及帷幕体侵蚀模块构成,并采用FEM数值法求解。工程实例计算结果表明帷幕体的防渗效果随着时间的推移而弱化,此主要源自帷幕体中Ca(OH)2一类可溶性物质的溶失。在整个模拟时段,帷幕体中的钙质始终处于溶解状态,其不同部位发生溶蚀的强度也不相同,帷幕体底部的溶蚀量要高于其上部的溶蚀量;靠近坝基上游侧的帷幕的溶蚀量要高于下游侧的溶蚀量。钙离子迁移主要由于水动力条件和弥散作用共同引起的,且坝基各点的钙离子浓度随时间呈非线性变化。
The seepage dynamic of the dam foundation is largely controlled by the intactness and water stopping effect of the curtain foundation of the dam foundation. However, due to the long-standing physical-chemical interaction of the groundwater, the seepage prevention performance of the curtain body decays. In order to be able to reproduce the process of dam foundation imperviousness attenuation, a multi-coupling model reflecting the anti-seepage aging of the curtain body was established based on the basic theory of seepage flow mechanics and hydrogeochemistry. The model consists of a seepage module, a solute transport module, a geochemical module and a curtain erosion module, and is solved by FEM numerical method. The engineering example shows that the anti-seepage effect of the curtain body is weakened with the passage of time, mainly due to the dissolution of soluble substances such as Ca (OH) 2 in the curtain body. During the whole simulation period, the calcium in the curtain body is always dissolved, the dissolution strength in different parts is not the same, the erosion amount at the bottom of the curtain body is higher than the dissolution amount at the upper part. The dissolution of the curtain near the upstream side of the dam foundation The amount is higher than the amount of dissolution on the downstream side. Calcium ion migration is mainly caused by hydrodynamic conditions and dispersion, and the calcium ion concentration at each point of the dam foundation changes nonlinearly with time.