基于FLO-2D数值模拟震区急陡型泥石流冲出量--以瓦窑沟为例

Numerically simulating the runout volume of debris flow at urgent steep gully in the earthquake areas based on FLO-2D--Illustrated with a case of Wayao gully

汶川地震后,震区的山体破碎严重,诱发泥石流、滑坡等地质灾害的临界阈值较低,其中诱发一类破坏性极大的急陡型泥石流。此类泥石流暴发历时较短、体积浓度和泥砂比重较大,产生较强"滚雪球效应"和"消防管效应"。工程措施对急陡型泥石流的FLO-2D数值模拟具有重要影响,因此以汶川震区瓦窑沟为例,采用FLO-2D模拟典型急陡型泥石流在非工程和工程措施下的冲出量,模拟精度达到86.4%。在工程措施下,泥石流分段淤积于拦挡坝后,大大减缓冲出量。模拟重现期为50年一遇时,工程治理下比非工程措施下的冲出量减少83.16%,冲出影响范围减少75.81%,平均堆积深度减少30.25%。研究结果可以为汶川震区急陡型泥石流的防灾减灾工程、早期预警等研究提供参考。

The mountain was seriously broken in the earthquake area after the Wenchuan earthquake. The critical threshold for inducing geological disasters such as debris flow and landslide was low. A type of urgent-steep gully debris flow was triggered, which led to extreme destruction. This type of debris flow has a shorter outbreak duration, a large volume concentration and a large average density, showing a strong "snowball effect" and strong "fire hose effect". The engineering measures have an important influence on FLO-2 D numerical simulation of urgent-steep gully debris flows. Therefore, FLO-2 D is used to simulate the runout volumes of typical urgent-steep gully debris flows under engineering measures and nonengineering measures scenarios respectively, taking Wayao gully in Wenchuan earthquake area as an example. The accuracy of numerical simulation results is 86.4%. The block dam in the circulation area can divide block debris flow into sections under the engineering measures, which makes the debris flow runout volume reduced. When the rainfall frequency is P =2%, under the engineering treatment measures scenario, the runout volume is 83.16%, the accumulation fan area is 75.81%, and the average accumulation depth is 30.25% less than those in the natural scenario. The research results can provide reference for disaster prevention and mitigation engineering and early warning of debris flow of urgent steep gullies in earthquake areas.