基于数值模拟的震区溃决型泥石流入流点选取探讨

FLO-2D模型假定下伏沟床固定,未考虑泥石流沿程侵蚀,但侵蚀作用带来的泥石流沿程补给是强震区泥石流的主要活动特性,在溃决型泥石流中侵蚀作用尤为强烈,忽略该侵蚀过程,将会造成流体规模的严重低估。本文选取汶川震区典型溃决型泥石流沟为研究对象,利用泥石流过程机制的分析,将沟床侵蚀结束的位置设置为入流点,即侵蚀/堆积的分界点。为确定溃决型泥石流入流点流量过程线,将沟道最后一级已溃决的堰塞体参数输入到BREACH模型中,获得与实际相吻合的溃口流量过程线,依据体积浓度划分清水流量过程线在入流点处输入进行模拟研究。引入同时考虑淤积范围与堆积方量的精度评估模型,结合实际暴发情况对模拟结果进行评估,结果表明基于FLO-2D的震区溃决型泥石流数值模拟可将入流点设置在侵蚀与堆积分界点处,为该模型在强震区溃决型泥石流冲出规模预测的应用上提供一定的科学依据。

Discussion on Selection of the Inflow Point of the Dam-Break Debris Flow Based on the Numerical Simulation Model

The FLO-2D model assumes that the underlying bed of the channel is fixed with no consideration of the erosion of the debris flow, but the supply from the debris flow erosion is the main feature of the debris flow activity in the co-seismal area. The erosion of dam-break debris flow is particularly strong and ignoring this will cause a serious underestimation of the run-out scale. To verify this hypothesis, this study selected the typical debris flow events in the earthquake area and set the inflow point, the boundary point of erosion and accumulation, at the end bed of the channel erosion according to the process mechanism of debris flow. At the same time, in order to determine the flow curve of the break debris flow, parameters of dam around channel outlets were input to the Breach model to obtain the simulation flow curve that matched the actual flow, the simulation was carried out by inputting the flow curve with the consideration of the volume concentration in the inflow point. The simulation results were compared with the actual situations of outbreak using the precision evaluation model, the results showed that the inflow point on the boundary of accumulation and erosion was suitable for the outburst debris flow, which can provide scientific reference for the accuracy and feasibility of applying the FLO-2D model in the run-out scale prediction of the dam-break debris flow.