高土石坝心墙水力破坏机制研究进展

Progress of study on hydraulic failure mechanism of clay core-wall in high earth-rockfill dam

心墙是高土石坝防渗体系的关键部位,在高库水压力的作用下,心墙可能产生水力破坏从而造成过量渗漏乃至溃坝的严重后果。预防心墙水力破坏的关键在于揭示心墙中初始渗漏通道的产生机理和条件。水力劈裂曾被广泛认为是心墙中初始渗漏通道的产生原因,简要回顾了土石坝黏土心墙水力劈裂研究的进展,讨论了水力劈裂理论在解释土石坝黏土心墙水力破坏机制方面的不足。近年来,在心墙压实黏土的剪切渗流特性研究方面取得了新进展,发现严重超固结的压实黏土在剪切后会形成高渗透性剪切带的试验事实。在此基础上提出了高土石坝黏土心墙水力破坏的剪切渗透弱面机制。触发剪切渗漏弱面的应力条件较传统水力劈裂判别的应力条件更容易满足,并且预测的渗漏位置更符合工程实际,因此在实际工程设计中应更重视高渗透性剪切带的评价和处置。

Core wall is the key component of high earth and rock-fill dams to cut off water flow through the dams, and hydraulic damage of the core wall under high water pressure could lead to excessive leakage or dam failure. To reveal the mechanism and triggering condition of the initial leakage channel in a core wall is the key issue in prevention of the hydraulic damage of the core wall. Hydraulic fracture was used to explain the cause of the initial leakage channel in the core wall under high water pressure. The progress of the study on the hydraulic fracturing of the clay core-wall in earth-rockfill dam is briefly reviewed herein, and then the deficiency of the hydraulic fracturing theory in the aspect of explaining the hydraulic failure mechanism of the clay core-wall in earth-rockfill dam is discussed as well. In recent years, new progress is achieved in the aspect of the study on the shear-seepage characteristics of the compacted clay of the core-wall;from which the experimental fact of that the overconsolidated compacted clay can form a shearing zone with high permeability is found out. On the basis of this, the shearing seepage weak plane mechanism of the hydraulic failure of the clay core-wall in high earth-rockfill dam is put forward. The stress condition to induce the shearing seepage weak plane can be more prone to be satisfied than that of the conventional identification of hydraulic fracturing, while the predicted location of leakage is more consistent with the engineering practice, thus more attention is necessary to be paid to the evaluation and treatment of the shearing zone with high permeability in the actual engineering design concerned.