拦砂坝失效条件下泥石流潜在危险性分析

Analysis of potential hazard of debris flows under failure conditions of check dams

受极端降雨的影响,泥石流灾害呈现多发、频发、致灾严重的特点。而采用拦砂坝等措施来防治泥石流是保护山区城镇的有效手段之一。随着时间的推移,部分拦砂坝已达到设计使用年限,存在因破坏失效而潜在危险性增大的问题。为了探明拦砂坝失效条件下的不同频率泥石流潜在危险性,以四川省金川县沙耳沟为研究区域,利用FLO-2D数值模拟软件模拟了无工程措施、拦砂坝正常运行和拦砂坝失效3种工况下的泥石流运动和堆积特征,并对泥石流危险性进行了区划。结果表明:工程失效与自然条件相比,最大堆积深度相差较小,平均堆积深度增加了2.57%~5.77%;最大流速和平均流速分别增加了0.1%~35.98%、1.95%~6.55%;冲出距离变远,冲出方量增加了3.14%~6.65%。相比无工程措施和拦砂坝正常运行条件,拦砂坝失效工况下高危险区面积分别增加了0.93%~3.39%、8.91%~17.93%;堆积范围分别增加了0.39%~0.83%、11.50%~22.50%。若拦砂坝失效,将产生巨大的泥石流潜在危险性,在极端天气下应加强对老化拦砂坝的监测预警。研究成果可为该地区地质灾害防治提供参考。

Affected by extreme rainfall,debris flow disasters are frequent and serious.The use of check dams and other measures to prevent and control debris flows is one of the effective means to protect mountain towns.With time elapsing,some check dams have reached the designed service life,so the potential failure risks are increasing.To explore the potential hazards of debris flows with different frequencies under the potential failure of check dams,a study was conducted in Shaergou Gully in Jinchuan County,Sichuan Province.We used FLO-2D numerical simulation software to simulate the movement and accumulation characteristics of debris flows under three working conditions:no engineering measures,normal operation of check dam and failure of check dam.And the hazards of debris flow were zoned.The results showed that compared with natural conditions,the difference between the maximum accumulation depth of engineering failure case was small,and the average accumulation depth increased by 2.57%~5.77%;the maximum flow velocity and average flow velocity increased by 0.10%~35.98%and 1.95%~6.55%,respectively;the runout distance got longer,and the volume of debris flow flushing out increased by 3.14%~6.65%.Compared with no engineering measures and normal operation conditions of the check dams,the area of the high-risk area under the engineering failure condition increased by 0.93%~3.39%and 8.91%~17.93%,respectively;the accumulation range increased by 0.39%~0.83%and 11.50%~22.50%,respectively.If the check dams fail,it will produce a huge debris flow potential danger,so the monitoring and early warning on aging check dams should be strengthened in extreme weather.The results can provide references for prevention and control of debris flow in the study area.