深厚覆盖层上高心墙坝地震惯性力动态分布系数研究

Study on the distribution of coefficient of seismic inertia force of high core rockfill dam located on the deep overburden

对于强震区坐落在深厚覆盖层(深度超过50 m)上的高土石坝,通过拟静力稳定分析结果初步判定其抗震稳定性是抗震设计的主要内容,其中水平向地震惯性力沿坝基覆盖层至坝顶的动态分布系数是关键。然而,现行《水工建筑物抗震设计标准》(GB 51247—2018)中地震惯性力动态分布系数多基于坐落在基岩上的高土石坝的动力响应规律确定,现有动态分布系数忽略了深厚覆盖层和地震动强度对地震动传播规律的影响。因此,以坐落在深厚砂砾石覆盖层上150 m级高黏土心墙堆石坝为研究对象,结合现行土石坝设计规范和国内已建高土石坝实例,基于统计平均的方法确定了坝顶宽度、坝料分区、坝坡坡比、覆盖层材料的静、动力特性等关键参数,深入探讨了150 m级高黏土心墙堆石坝在小震(0.1 g)、中震(0.2 g)和大震(0.4 g)规范谱地震动作用下不同深度砂砾石料覆盖层的动力响应分布规律,进而总结归纳出不同深度覆盖层下150 m级高黏土心墙堆石坝的水平向地震惯性力的动态分布系数,将其引入到拟静力法稳定分析中,最后基于最危险滑动面和最小安全系数与现行规范所得结果进行对比分析。研究结果表明,小震(0.1 g)和中震(0.2 g)下采用文中推荐的考虑深厚覆盖层和地震动输入强度影响的水平向地震惯性力动态分布系数时将得到更符合工程实际的评价结果。研究成果可为深厚覆盖层上的高土石坝抗震设计提供参考依据。

For the high rock-fill dam located on the deep overburden layer(more than 50 meters deep),the main content of the seismic design is the seismic stability analysis through the pseudo-static stability analysis results,in which the dynamic distribution coefficient of the horizontal seismic inertial force along the overburden is crucial.However,in the standard for seismic design of hydraulic structures(GB 51247-2018),the dynamic distribution coefficient curve of seismic inertia force is mainly based on the dynamic response law of high rockfill dams located on bedrock,which ignored the influence of deep overburden and ground motion intensity.This paper took the 150m high clay core rockfill dam located on the thick gravel stone overburden as the research object,combined with the design specifications of high rockfill dams built in China,based on the method of statistical averaging,determined the dam crest width,dam slope ratio,static and dynamic parameters of the overburden material and other key parameters,and deeply discussed the dynamic response distribution law of the sand gravel overburden of high clay core rockfill dam with gravel overburden at different depths under the spectral ground motion of small earthquakes(0.1 g),medium earthquake(0.2 g)and large earthquake(0.4 g),and then summarized the proposed coefficient of horizontal inertial force of 150m high clay core rockfill dam under different depths of overburden.Finally,the paper compared the stability analysis results based on pseudo-static method with the specifications.The research results showed that the proposed coefficient of horizontal inertial force recommended in this paper,which took into account the influence of deep overburden and ground motion input intensity while under the spectral ground motion of small earthquakes(0.1 g)and medium earthquake(0.2 g)under a number of depths of overburden,will get more in line with the actual evaluation results of the project,and can provide scientific basis for designers to design high rockfill dams located on deep overburden.