重力坝中劈头裂缝开裂分析

Cracking analysis on vertical crack of gravity dam

混凝土重力坝中的表面裂缝在蓄水后容易扩展成劈头裂缝。本文通过三维有限元仿真计算,分析上游表面裂缝在蓄水后,水沿着裂缝入渗至坝体内部,对内部混凝土造成的冷击影响,进而判断表面裂缝扩展成劈头裂缝的可能性。通过工程实例计算表明,上游表面裂缝扩展成劈头裂缝主要原因是水沿着裂缝入渗至坝体内部,温度应力叠加水的压力,在裂缝周端引起很大的拉应力,进而使裂缝向纵深扩展。通水冷却措施对改善缝端应力效果并不明显,防止劈头裂缝的有效方法是在蓄水前对坝体上游表面裂缝进行封堵处理。

The surface crack on upstream face of concrete gravity dams is prone to be extended into the vertical crack after the impoundment. Through a 3 - D finite element simulation, the cold impact on the inner concrete caused by water infiltrating into the body of dam along the surface crack after the impoundment is analyzed herein, and then the possibility of that the surface crack is extended into the vertical crack is estimated as well. Based on the calculation made on an actual engineering case, it is indicated that the main causation of the extension of the surface crack into the vertical one is the infiltration of water into the dam body of dam along the crack, from which large tensile stress occurs around the crack caused by the superposition of the tempera- ture stress on the water pressure, thus makes the crack deeply extended. The effect of improving the stress around the crack by water cooling is not so significant, thus the effective method to prevent the occurrence of the vertical crack is to block up the up- stream surface crack of dam body before the impoundment.