组合式格栅装置解决泥石流重力式拦砂坝的淤积问题

Combined Metal Grid Device Designed to Desilting Gravity-Type Check Dam

重力式拦砂坝因坝后淤积、库容不足,泥石流拦蓄作用失效,后续翻坝泥石流坠砸下游坝基,是拦砂坝损毁的主要成因之一。采用工程措施清淤调库,提高拦砂坝淤积满库后的可持续利用,是泥石流防治工程设计中面临的实际问题。本文通过理论分析、模型实验等研究方式分析了重力式拦砂坝的满库状态,设计了鱼脊型格栅装置或组合格栅装置,构建新型拦砂坝体系,研究了泥石流的调控效果。结果表明:(1)重力式拦砂坝库容内的泥沙堆积体形成的缓坡段与组合式格栅装置共同作用可实现对泥石流的调控;在小流量的水石流情况下缓坡段的自然分选作用明显,而在流量较大的稀性泥石流条件下组合格栅的拦粗排细作用效果显著;(2)组合格栅的拦粗排细率与其作用的泥石流固体物质颗粒级配参数fc′呈先增大后减小的抛物线关系;在水石流和泥石流条件下,fc′分别达到41.5%和36.9%时,拦粗排细率达到最大,即组合格栅的拦粗排细效果最优;(3)新型拦砂坝体系对泥石流泥沙总分离率与粗颗粒分离率均与形成泥石流的固体物质颗粒级配参数fc呈正比关系;泥石流初始容重越大,调控后容重减小越明显。本研究为继续发挥满库后的重力式拦砂坝的泥石流调控作用提供了方案,具有重要的工程实践意义。

Gravity-type check dams built in the valleys with high occurrences of debris flow are inclined to fail in regulating of debris flows after heavy silting and decreasing storage capacity occurring in the dams;subsequent overturning of debris flows fall on the downstream dam foundation,quite often resulting in dam damages,even broken-down.The use of engineering measures to remove sediment and improve the sustainable use of check dams after full reservoir is a practical problem in the design of debris flow prevention and control engineering.In this study,it investigated the performance of gravity-type check dams by theoretical analysis,model experiment and other research methods,and then a fish-ridge type metal grid structure(a herringbone water-sediment separation structure)or a combination metal grid structure was introduced to build up a new type of barrier system for regulation of debris flow,and the control effect of the system was examined.We have the following results:(1)Gentle gravel slope behind dam formed by sediment accumulation because of debris flow transportation in the reservoir of check dam and the combined metal grid structure can jointly realize the regulation of debris flow.(2)Under entrainment of water-stone flow,evidently the gentle gravel slope had an active role in grain sorting and sieving,whereas under relatively larger erosion of watery debris flow,it was remarkable in the effect of trapping coarse debris and discharging fine particles.(3)The particle grade parameter(f c′)of solid component in an occurrence of debris flow after being sorted and sieved by our advocated structure of combination metal grid described a parabolic curve of first increasing and then decreasing,and it stood for its drainage effect.In case subjected to water-stone flow and watery debris flow,f c′could reach 41.5%and 36.9%respectively,with a maximum drainage effect,the best function of trapping coarse debris and discharging fine particles.The separation efficiency for a bulk of debris flow sediment or its coarse component by a combined metal grid structure were directly proportional to the particle grade parameter(f c)of the original solid component of debris flow.The greater the initial bulk density of debris flow,the more obvious the reduction of bulk density after regulation was.This study provides a scheme for further exploiting gravity-type check dam with full reservoir in regulating debris flow discharge.It is engineering practical.