为研究坝体颗粒级配对堰塞坝溃决特征的影响,引入平均粒径D₅₀作为主要指标,以不同均值粒径的土体作为研究对象,通过开展不同颗粒级配条件下堰塞坝溃决特征试验,分析堰塞坝体在3种不同工况下的破坏模式和溃决特征。结果表明,①工况3条件下坝体溃决历时是工况1的2.5倍,而溃决洪峰流量减小了约60%,说明坝体平均粒径对坝体的溃决特征有显著影响,平均粒径越大,坝体整体抗冲刷能力越强,溃口发展速度越慢,坝体越稳定,溃决洪峰流量就越小,达到洪峰流量的时间也相对滞后; ②平均粒径和渗透系数可拟合成二次函数曲线,随着平均粒径的增大,渗透系数也随着增大; 以孔隙水压力的变化特征为依据,把溃决过程分为3个阶段,即上游库水位增加阶段、水流漫顶下渗阶段、坝体溃决阶段。

Particle size distribution is one of the key factors affecting the dam outburst. In order to investigate the influences of particle size distribution of dam on dam outburst features, the average particle size of D50 are introduced as the main index, with different mean particle size of soil as the research object, throuhg the development of experimental dam outburs features under the different gradation conditions, analysis of the dam breaching character under three different conditions(the first condition: D50=5.4 mm; the second condition: D50=6.8 mm; the third condition:D50=9.2 mm), the preliminary conclusions are as follows:(1)The test results show that the dam under the third condition(D50=9.2 mm)the outburst duration is 2.5 times that of the first condition(D50=5.4 mm), while the peak flow rate is reduced by about 60%. This indicaes that the average particle size of the dam has a significant influence on the characteristics of the dam outburst, the larger the average particle size, the greater anti-erosion ability of the dam will be, the slower the break development, the smaller the outburst peak flow volume is the time to reach peak flow volume is also lagging behind;(2)the average particle size and permeability coefficient can be proposed to be a quadratic function, with the average particle size increaing. The permeability coefficient is also increasing; based on characteristics of pore water pressure, the breaking process is divided into three stages: upstream water level increase stage, water overtopping infiltration stage.dam outburs stage.