超高心墙堆石坝拱效应分析

心墙拱效应会降低心墙竖向应力,诱发水平裂缝,从而产生水力劈裂,危害大坝安全,这在超高心墙堆石坝中尤为显著。以某300 m级高心墙堆石坝为研究对象,通过实测资料和有限元计算分析了坝体应力沉降规律,探讨了坝体材料对心墙拱效应影响状况及土拱作用较强的部位,进而评估了因拱效应导致水力劈裂的可能性和心墙应力传递随高程的折减情况。研究表明,心墙最大沉降的计算值略低于实测统计值,坝体内部没有出现拉应力;心墙坝基处下游部位拱效应影响较大,坝基以上部位心墙坝轴线处拱效应明显,基本不会因拱效应影响导致出现水力劈裂;拱效应受心墙与坝壳变形模量比和心墙泊松比影响较大;780 m高程以上部位土拱作用明显,导致上部应力向下传递的折减较大。

Analysis of soil arching in high core-wall rockfill dam

Soil arching effect of core wall could reduce its vertical stress and induce horizontal fractures, resulting in hydraulic fracturing that threatens dam safety, and this is particularly significant in high core-wall rockfill dams. This study has focused on a 300 m high-grade core-wall rockfill dam. We herein analyze the stress in the dam body and its settlement trend using FEM simulations and monitored data, then discuss the effects of dam materials on the core wall and the locations with severe soil arching effect. Finally, we evaluate the possibility of hydraulic fracturing caused by soil arching and describe how the stress transfer in core wall varies vertically with elevation. Results show that the largest settlement of core wall calculated by FEM is slightly smaller than the monitored value, and no tensile stress in the dam was observed. On the base of core wall the arching effect is obvious in the downstream, while above the base it can be obviously observed only near the dam axis but not strong enough to cause hydraulic fracturing. Generally, the arching effect is greatly influenced by the elastic modulus ratio of core wall over dam shell and the Poisson's ratio of core wall. Above elevation 780 m, the soil arching effect is quite severe, causing a greater reduction in top-down stress transfer.