水库淤积物密实变化对冲淤计算与库容影响的研究

Influence of sediment volume shrinkage on alluviation calculation and reservoir capacity

多泥沙河流水库淤积物为中细颗粒(粒径d<0.5 mm)泥沙时,初始淤积物的体积与干密度具有不稳定性,随着淤积厚度与淤积年限的增加,泥沙固体颗粒逐渐被压实,淤积物干密度增大,从而发生缩体现象,对断面法冲淤计算及水库库容变化具有重要影响。为此,在淤积物密实演化物理模式基础上,分析了淤积物体积缩小与湿密度和干密度变化之间的关系,导出了淤积物体积缩小的干密度计算公式,探讨了淤积物密实沉降对断面法年度冲淤计算的影响和淤积物密实沉降累积历程,结合三门峡水库实测资料确定了该库淤积物初期和极限稳定期干密度取值,进行了密实缩体实例计算与分析。研究表明:以各年度断面法测算的冲淤量为基础所得的水库多年累计冲淤量,并不能真正代表实际库容的损失;大量淤积物长历时密实过程会增大水库库容。

The volume and dry density of the initial sediment are unstable when the sediment is small particles(particle size d<0.5 mm).With the increase of the thickness and years of deposition,the sediment particles are gradually dense,and the dry density of the sediment is increased,thus the phenomenon of compaction occurs,which has an important influence on the calculation of cross-section method and the change of reservoir capacity.Based on the physical model of sediment compaction process,the relationship between the volume reduction of sediment and the changes of wet density and dry density is analyzed.The calculation formula of dry density of sediment volume reduction is derived,The influence of compaction settlement of sediment on annual erosion and deposition calculation by section method and the accumulation course of compaction settlement of sediment were discussed,Combined with the measured data of the Sanmenxia Reservoir,the values of dry density in the initial stage and the ultimate stable stage of the deposit are determined.The case calculation and analysis of the dry density of the reduced volume are carried out.The results show that the accumulated amount of scour and deposition of the reservoir based on the annual cross-section method could not really represent the loss of the actual storage capacity,and the long-term volume reduction of a large amount of sediment will increase the storage capacity of the reservoir.