为分析重力坝下游折坡点位置对其抗震性能的影响,从震害工程及有限元计算两方面分析重力坝的抗震性能。结果表明：下游折坡点位置过低将对重力坝抗震性能带来不利影响；坝颈部位应力随下游折坡点位置的降低而增大,且增幅随坝高的增加而增大。为保证大坝具有良好的抗震性能,工程设计中下游折坡点位置不宜取太低,在8度及以上地震烈度区,100 m高重力坝折坡点位置不宜低于坝高的20%。云南某水电站水库计算结果表明：大坝在设计地震作用下,坝颈部位产生了明显的应力集中,并出现裂缝；当地震超载系数为1-17时,坝颈部位上下游的裂缝贯通,大坝抗震性能较差,在工程设计中应合理提高下游折坡点的位置。%The influence of the downstream turning point on the seismic performance of a gravity dam was studied through earthquake projects and finite element calculation. The results show that a position of the downstream turning point that was too low had adverse effects on the seismic performance of the gravity dam. The stress of the neck of the dam increased with the descending position of the downstream turning point and the ascending height of the dam. To ensure good seismic performance of the dam, the position of the downstream turning point should not be too low in project design;it should not be lower than 20% of the height of the dam for a 100 m-high gravity dam in areas with an earthquake intensity of eight or an even higher degree. Linear elastic and nonlinear dynamic finite element analysis were conducted for a practical project in a hydropower station in Yunnan Province. The calculation results show that, under the design earthquake effects, obvious stress concentration and cracks appeared in the neck of the dam. When the earthquake overload coefficient was 1-17, the upstream cracks joined the downstream cracks in the neck of the dam, indicating that the seismic performance of the dam was very poor. The downstream turning point should be reasonably improved in project design.
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