土石坝抗震稳定的极限能力与评价标准研究

Study on ultimate capacity of seismic stability and evaluation criteria of earth-rockfill dams

目前土石坝极限抗震能力的评判指标尚不统一,评价标准仍不明确,且缺乏合理的依据。本文基于地震反应分析,从坝坡抗震稳定性和地震滑移变形对土石坝的极限抗震能力进行了研究,提出以地震滑移变形发生突变作为土石坝抗震稳定极限能力的判定标准。以某沥青混凝土心墙堆石坝为例进行了计算分析,当地震峰值加速度为0.55g时,上、下游坝坡Fs<1.0的累积时间分别为2.5 s和2.8 s,地震滑移变形分别为0.46 m和0.55 m,并产生了明显的突变。由此,可判定大坝的极限抗震能力为0.55 g。结果表明,土石坝的抗震薄弱部位位于坝顶1/5坝高范围内,符合实际震害的一般规律,建议该区域应采取合理的抗震措施。

At present, the evaluation indexes and criteria are not only clear, but also lack of the reasonable basis. According to seismic time-history analysis, the ultimate seismic capacity of earth-rockfill dams is studied from the angle of the seismic stability of the dam slopes and the seismic sliding displacement. In this paper, the seismic sliding displacement mutation of the dam slope is chosen as the evaluation criterion of the ultimate capacity of seismic stability. Then, a case study of an asphalt concrete core rockfill dam which is built in west area of China, is carried out. It is shown by the results that when the seismic peak acceleration reaches 0.55 g, the cumulative time of Fs<1.0 for the upstream and downstream dam slopes is 2.5 s and 2.8 s, and the seismic sliding displacement is 0.46 m and 0.55 m, separately. Moreover, the seismic sliding displacement of the dam slopes is mutated which is indicated that the ultimate seismic capacity of the dam is 0.55 g. Meanwhile, the weak region of the earthquake-resistant dam is the area that 1/5 of the dam height from the crest, which is coincided with the actual earthquake damage. In consequence, it is suggested that some effective seismic measures should be proposed in this area.