嫩江佰大街防浪林消浪机理物理实验研究

Wave elimination mechanism of wavebreak forest by physical experiments in Baidajie Dike, Nenjiang River of northeastern China

【目的】以嫩江佰大街堤防为研究对象,研究不同因素对嫩江干流防浪林消浪效果的影响以及合理设计防浪林优化布局。【方法】根据重力相似准则,通过合理的比尺缩放将研究区防浪林缩小至实验室水槽中,构建合适的防浪林物理模型,模拟防浪林植被与波浪的作用过程。其中波浪由造波机生成,防浪林采用模型树模拟。物理模型的实施方案,主要采用控制变量法,即通过单因素变化的方法,选取防浪林林带宽度、排列方式、密度、树型、滩地波高作为消浪影响因素,进行分组实验,模拟某一因素变化下,防浪林消浪效果的变化,确定各个影响因素对防浪林消浪效果的影响;并根据实验结果,综合一些较为复杂的影响因素,提出防浪林优化设计方案。【结果】实验结果表明:合理的防浪林树型条件下,30~40 m的防浪林林带宽度的消浪系数在30%以上,继续增大防浪林林带宽度,消浪系数增加并不显著。考虑到经济合理等因素,40 m的防浪林带宽度较为合理;等边三角形的排列方式的防浪林消浪效果相对较优,并且能满足更大的行株距,更适于防浪林生长的光照条件。植被密度的增加能够提高消浪系数,但当防浪林密度大于0.17株/m^2时,消浪系数提高不显著,当防浪林密度采用0.17株/m^2时能够充分的保证行株距,更有利于林带的生长。同时防浪林树冠部分的消浪效果最佳,并且当波高处于树冠位置时,波高越大,消浪效果越好。【结论】因此,在合理的树型条件下,研究区防浪林林带宽度采用40 m,排列方式为等边三角形,密度为0.17株/m^2左右时为防浪林优化布局。

[Objective] Taking the Baidaijie Dike in Nenjiang of northeastern China as the research object,this paper aims to study the influence of each factor on wave-elimination effect of Nenjiang Mainstream wavebreak forest, and to optimize the layout of the forest. [Method] According to the gravity similarity criterion, the forest in the study area is reduced to a laboratory sink by reasonable scale scaling to simulate the process of the effect of the vegetation on the wave. In the experiments, waves are generated by the wave generator, the wavebreak forest is simulated by the model tree and thus a suitable physical model of the wavebreak forest is constructed. The main control variable method is adopted, and the width, density,arrangement mode of wavebreak forest, tree shape and wave height on the beach were taken as the influential factors. Grouping experiments were conducted. And in each group, the changes of waveeliminating effect of wavebreak forest under the change of a certain factor were simulated to determine the influence of each influencing factor on the wave-eliminating effect. And based on the experimental results of the optimization scheme, some complicated factors are combined and the optimal design scheme is proposed. [Result] The results showed that under reasonable conditions of tree shape, the wave-elimination coefficient of 30-40 m of the width of the forest was above 30%, and the increase of the wave-elimination coefficient of the larger forest width was not significant. Taking into account the economic and rational factors, 40 m of the width of the forest was more reasonable. Forests with equidistant triangles arranged mode were relatively superior, and can meet the needs of greater row spacing and more suitable for the conditions of light, growth and health of the wavebreak forest. The increase of vegetation density can improve the wave elimination coefficient, but when the vegetation density was more than 0.17 plant/m^2, the wave elimination coefficient cannot be increased significantly. And it is suggested that the vegetation density should be about 0.17 plant/m^2, which can fully guarantee the plant spacing, more conducive to the growth of forest belt. Meanwhile, when the wave height is in the crown position, the wave-eliminating effect is good;and the higher the wave height was, the better the wave-elimination effect was. [Conclusion] The optimal design scheme in research area is under the reasonable tree type condition, the width of the shelterbelt is 40 m,the arrangement is equilateral triangle, and the density is about 0.17 plant/m^2.