心墙是否会发生水力劈裂关系土石坝的安全，该问题的难点和关键之一是水力劈裂的发生机制和条件。利用自制模型，在2种不同加压速率条件下，对有无初始裂缝和5种不同初始裂缝深度的试样进行了水力劈裂试验；结合数值模拟和CT观测试验，验证了水力劈裂的楔劈效应机制—当水压力作用在初始裂缝形成的劈背上，引起劈刃上的力超过临界值时就可能导致发生水力劈裂。研究结果表明：初始裂缝深度越大、加压速率越高，越容易发生水力劈裂。为避免土石坝发生水力劈裂破坏，应注意心墙迎水面的施工质量和平整性，宜采用较慢的蓄水方案。

The safety of earth-rock dam relies on whether hydraulic fracturing will happen or not in the core wall. One of the key issues is the mechanism and conditions of hydraulic fracturing. By using the self-made test apparatus, specimens without initial cracks and with 5 different depths of initial cracks are prepared for hydraulic fracturing laboratory tests under 2 different loading rates. Combined with numerical analysis and CT tests, the mechanism of hydraulic fracturing is confirmed as wedge splitting effect. When water pressure is applied onto the “cutting back” formed by initial cracks and the induced force on the “cutting blade” exceeds the critical value, it possibly leads to hydraulic fracturing. Test and analysis results show that the deeper the initial crack on the surface of specimen, and the higher loading rate, the easier hydraulic fracturing occurs. In order to prevent from hydraulic fracturing on earth-rock dams, attentions must be paid on the construction quality and smoothness of upper-surface of the core wall, and the water level of reservoir is recommended for slowly raising.