均质土坝坝体材料冲蚀特性试验研究

Experimental study of erosion characteristics of soils in homogeneous embankments

土石坝坝体冲蚀特性直接关系到坝体是否溃决,何时溃决,是土石坝溃坝研究的核心难题.本文通过物理模型试验,对不同坝体土料冲蚀特性进行研究.基于大量试验研究,分析了土料干密度、净切应力、冲刷系数、泥沙指数等与土体冲蚀特性的关系.提出泥沙指数宜依据土料冲蚀速率和净切应力确定,而不宜设为定值1(黏性土)或者1.5(非黏性土);冲刷系数与泥沙指数呈现明确的对数关系;起动切应力对土料冲蚀速率影响权重较大;利用泥沙指数变量,可以有效地区分坝体土料的抗冲蚀能力,并评估坝体抗溃决能力.

The erosion characteristics of soils in homogeneous embankments is the key problem of dam breach which is directly related to the breach formation and the rate of breaching. The Erosion characteristics of several soils in embankment have been researched. On the basis of the erosion test results, the effects of dry density, net shear stress, sediment detachment exponent on the rate of erosion were analyzed. According to the results the sediment detachment exponent should be calculated based on the erosion velocity and net shear stress. It is not convenient for analysis if the value of sediment detachment exponent was set 1 for cohesive soil or 1.5 for noncohesive soil. It has an definite logarithmic relationship between erosion coefficient and sediment detachment exponent. The critical shear stress has an significant effect on the rate of erosion of soils. The erosion resistance of soils in embankment dams and the dam safety can be evaluated well by using the sediment detachment exponent.