采砂坑纵剖面尺寸对卵石河道河床演变影响数值试验——以石亭江双盛段为例

Numerical Simulation Study on Effect of Different Longitudinal Profile Dimensions of Sandpit on Riverbed Evolution of Pebble Channel——A Case of Shuangsheng Section of Shiting River

人类活动与河流的河床演变形态、河相关系息息相关,人类活动使得山区河流在河道形态、泥沙运动等方面会发生一系列的变化;近些年建筑用砂需求量剧增,人们大量采挖河砂,改变了河流原有的河床边界,对河流的演变产生了诸多影响。研究河道采砂对河床演变的影响具有重要的学术及实践意义。本文依托HEC-RAS泥沙计算模块,以石亭江双盛段为研究对象,结合野外调查实际情况,拟定数种采砂坑工况,研究采砂坑纵剖面尺寸对河道河床演变的影响。根据资料和野外调查情况,首先拟定HEC-RAS河道模型断面及水流和泥沙边界条件,然后在采砂方量及采砂坑宽度相同的条件下,拟定5种不同纵剖面尺寸(深长比)的采砂坑,利用HEC-RAS泥沙计算模块进行数值模拟试验,对试验结果中河道主槽深泓点高程及断面沖淤量数据进行统计和分析。结果表明:人工采砂对河床整体的下切起促进作用,长浅型采砂坑比短深型采砂坑更能促进河床下切;采砂坑上下游河床下切变化不同,随着采砂坑深长比的增大,上游河床下切深度减小,下游下切深度呈现先减小后增大的趋势;采砂坑会改变河道局部坡度,上游河道局部坡度增大,下游河道局部坡度减小。试验研究了不同纵剖面尺寸采砂坑存在时,河床演变的变化状况,结论可对涉河工程的防护与设计及流域采砂规划提供一定的参考。

Human activities are closely linked to the riverbed evolution and the hydraulic geometry of river,which make the mountains river a series of change in morphology and sediment movement. In recent years,with the rapid increase in the demand for building sand,people mined river sand on a large scale,which changed the original river bed boundary condition and had considerable impact on riverbed evolution. Studying the influence of sand mining on the riverbed evolution of rivers has important academic and practical significance. Based on the HEC-RAS sediment calculation module,in combination with the field investigation,the numerical simulation were conducted for several kinds of sandpits in order to study the influence of different longitudinal profile dimensions of sandpit on the riverbed evolution of rivers. According to the data and the field investigation,firstly the river sectional information and boundary condition were determined. And then on the condition that the volume and width of sandpit was almost same,five kinds of sandpits with different depth-length ratio was set up. After simulation by HEC-RAS sediment calculation module,the data of the reach longitudinal profile and sediment erosion or deposition of every section were counted and analyzed. The results indicated that the erosion of riverbed was amplified by artificial sand mining and negatively correlated to the depth-length ratio of sandpit. In addition,with the increase of depth-length ratio,the erosion of upstream declined,while the erosion of downstream declined at first but then grew. What's more,Sandpit would change the channel local slope and the upstream local slope increased,while the downstream local slope decreased. The conclusions can provide certain reference to the protection and design of across river buildings and exploiting plan.