基于物理模拟试验的泥石流汇江效应初步研究

Effect of debris flow' converging into river on the basis of physical simulation experiments

为有针对性地预防和斩断泥石流汇江诱发的灾害链,以四川省汶川县映秀镇红椿沟"8·14"特大泥石流为原型,建立泥石流汇江物理模拟模型,通过5组17次物理模拟试验,研究交汇角、主河流速、泥石流含水率、一次入汇固体总量对泥石流汇江效应的影响,及物源对堵江模式的影响。试验表明:当交汇角为90°时,最容易发生堵江现象;河流流速越大,冲刷及携带颗粒的能力越强,交汇堆积区物质的体积越小;当物源含水率接近0.85时,交汇处堆积体体积最大;交汇区堆积体体积与一次性固体物源总量成线性关系,其增长幅度较其他影响因素(如交汇角、流速等)大;当物源体积较小时,易形成水下潜入式坝;当物源体积较大时,一部分泥石流形成潜入坝,另一部分保持在水面以上运动,泥石流中的细颗粒被河水带走,粗颗粒在交汇处保留造成局部堵塞甚至完全堵塞;试验中物源混合物重度试验值、流速反算值与红椿沟泥石流实际值基本吻合,验证了物理模拟试验的准确性。

As for prevention and cutting off the disaster chain induced by debris flow＇ converging into river,taking the debris flow happened on August,14 th at Hongchun Ditch,Wencuan County as the prototype,the physical simulation model is established,and 5 groups of 17 physical simulation tests are used to study the main factors that influence the debris flow＇ flowing into river. The results are that,the intersection angle of 90°is the easiest condition to block the river. The more rapid the flow speed of the main river is,the stronger the ability of its scouring and carrying particles is and the smaller the volume of accumulation at intersection zone is. When the moisture content is close to 0.85,the accumulation volume reaches the maximum. Accumulation volume has a linear relationship with the total amount of disposable solid source,and the total amount contributes to a bigger growth rate on accumulation volume than other factors,such as intersection angle and flow velocity. It＇s easy to form the submerged dam below water if the source volume of debris flow is small. When the source volume of debris flow increases gradually,one part of debris flow forms into submerged dam,the other part remains its movement above water,and then the fine particles is taken away by the river while the coarse one remains at the intersection zone which leads to blocking the river partially or totally. Gravity of mixture in test and flow velocity by back calculation is in accord with the Hongchun Ditch debris flow basically,and it verifies the accuracy of the physical simulation experiment.