泥石流梁式格栅坝泥砂粒径调节试验研究

Experimental Study on Sediment Size Regulating of Beam Type Debris Flow Check Dam

梁式格栅坝是泥石流防治工程中一种常见的透过型拦砂坝,具有拦粗排细的独特功效。通过室内水槽模型试验,探究了梁式格栅坝对泥石流泥砂粒径的调节特性。研究表明,梁式格栅坝在试验工况下均表现出一定的粒径调节作用,但在不同条件下差异明显,对于水石难分的高容重泥石流难以达到较好的粒径调节效果。分析认为,透过型拦砂坝的粒径调节可能是其容重调节的原因,坝体拦截了大部分粗颗粒物质,使泥石流体的结构变化,导致泥石流浆体能悬浮和输移的最大颗粒粒径变小。其次,提出了一种可用于透过型拦砂坝泥砂粒径调节效率的评价方法,并对比分析了该方法与现有常用评价方法的优势与合理性;基于模拟试验结果,通过多元非线性拟合,得到了新评价方法下考虑泥石流性质、过坝前运动状态和坝体尺寸的影响因素的泥砂粒径调节效率计算公式,可为梁式格栅坝设计中粒径调节效率的预测评估提供参考。此外,试验发现,梁式格栅坝泥砂粒径调节效果还受其拦截泥石流时的闭塞表现的影响。

Beam dam,which is an open-type check dam,has a good application in debris flow hazard mitigation.In this paper,a series of flume experiments were conducted to investigate the characteristics of the beam type debris flow check dam on sediment size regulating.The grain compositions before and after debris flow passing through the beam dam were obtained by the oven and vibrating screen.The experimental results reveal that the beam type debris check dam has high performance on size regulating.But it performs relatively low regulating efficiency for debris flow with high bulk density in which the water and blocks are difficult to be separated.Analysis result supports that the regulating capacity of the beam dam depends on the bulk density.Secondly,a new evaluation index considering grain size was proposed and compared with the common index in the previous studies.The analysis indicates that the regulating efficiency decreases first and then increases with the increase of relative opening,and reaches the minimum value at a relative opening of about 1.5.Furthermore,based on the experimental data,a calculated formula for sediment size regulation was obtained.It can provide a reference for practical engineering.Additionally,the regulating effect also was influenced by the blocking performance in the tests.