大型人工输水渠道高填方段溃决洪水情景

Burst flood scenario of high-filled section of large scale artificial water supply channel

为防范大型人工输水渠道的高填方段在超常外力下一旦溃决无法用概率表征的潜在风险,需建立适宜的情景分析手段,以模拟与评估不同溃口规模下多种调控手段联合运用在应急处置中的有效性。利用中国水利水电科学研究院自主研发的洪涝仿真模型,通过改进立交河道计算单元的拓扑关系和退水闸模拟方式,建立了渠道一维、溃口流量及两岸二维同步耦合计算的溃堤洪水淹没模型。以某大型人工输水渠道典型高填方段为例,分类对比分析了不同溃口宽度、关闸时间和退水闸是否启用等共12种情景下的洪水淹没特征变化。结果表明:溃口宽度的增加对溃决洪水淹没范围和程度的影响较小;关闸时间越早,越可以有效减少淹没区的面积和水深,且在3h内效果更明显;当地形和构筑物条件有利于洪水扩散时,及早关闸对淹没范围的减小幅度更大;在洪水不容易扩散的区域,及早关闸对淹没水深的减小幅度更大;退水闸启用后对淹没的减轻作用与退水闸和溃口之间的相对位置和距离有关,位于溃口上游且距离越近时越有效。研究可为大型人工输水渠道制定或完善相应应急预案提供基本的手段和依据。

To prevent the high-filled section of a large-scale artificial water conveyance channel from breaking under abnormal external forces,it is necessary to establish an appropriate scenario analysis method to simulate and evaluate the effectiveness of the combined application of multiple control measures in the emergency response under different breach scale.Using the flood simulation model independently developed by the China Institute of Water Resources and Hydropower Research,by improving the topological relationship of crossed channels and simulation method of recession sluices,a dike break flood inundation model of one-dimensional channel,breach flow,and two-dimensional simultaneous coupling calculation on both banks was established.Taking a typical high-filled reaches of a large-scale artificial water supply channel as an example,the changes in flood inundation characteristics under 12 scenarios,including different breach width,gate closing time,and whether the retreat gate is opened or not,are classified and analyzed.The results showed that:the increase of breach width had less impact on inundation extent and degree of outburst flood;the earlier the closure time of sluice gates was,the better the decrease of inundation area and water depth was,while the effect was more obvious during the first 3 hours after dike-breaking happened.When the terrain and ground objects distribution were conductive to flood diffusion,closing the sluice gate early could decrease more inundation area,otherwise,in areas where flood was not easy to spread,it was more effective for the decrease of inundation depth.The mitigation function of recession sluice for inundation was relevant to the relative position and distance between the gate and breach,the sluice located in the upper stream of the breach with closer distance was more effective to decrease the inundation.The basic method and basis are provided for the formulation or improvement of corresponding emergency plans of the large-scale artificial water supply channel.