| 王乐,杨旭博,王大宇,张尚弘,吴雪.河床表层冻融作用下推移质输移特征研究[J].水利学报,2023,54(12):1485-1495 |
| 河床表层冻融作用下推移质输移特征研究 |
| Freeze-thaw effect of bed surface on bed load transport behaviour |
| 投稿时间：2023-04-21 |
| DOI：10.13243/j.cnki.slxb.20230235 |
| 中文关键词: 冻融作用 推移质 输沙率 级配组成 河床稳定性 |
| 英文关键词: freeze-thaw effect bed load transport rate grain size distribution bed stability |
| 基金项目:中国水利水电科学研究院基本科研项目(SE110145B0022021，SE0199A102021);国家自然科学基金青年科学基金项目(52009041) |
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| 中文摘要: |
| 高纬度河流系统常会经历季节性冻结与融化。为揭示冻融作用对床面推移质运动的影响，本研究以未经历冻融过程的常规室温(20 ℃)推移质输沙实验结果为基准，保证实验条件不变，开展了均匀沙与非均匀沙床表层冻融后的室温(20 ℃)推移质输沙实验，综合比较了冻融作用影响下推移质输沙率与级配组成特征。结果表明，河床表层冻融后的推移质输沙率均高于无冻融作用的推移质输沙率，据此提出了有冻融影响与无冻融影响下的推移质输沙率比值ζ。研究显示，冻融作用下的推移质输沙率呈有规律变化：剪切力较小时ζ较大，剪切力较大时ζ减小并逐渐趋于1.0;非均匀沙中，随着泥沙粒径增大，各粒径组的ζ逐渐减小;低流量驱动时，冻融作用对非均匀输沙级配组成的影响显著，并随着流量增大而逐渐减弱。本研究剖析了冻融作用对推移质输沙率与级配组成的影响，有助于认识冰冻区河流的河床稳定性与河床演变情势。 |
| 英文摘要: |
| High-latitude rivers generally experience seasonal freeze-thaw process, and the impact of freeze-thaw process on riverbanks dynamics and instability has been widely reported.By contrast, bed-load transport behaviours in alluvial rivers under the freeze-thaw action is still unknown.As such, two comparative experimental series were executed to isolate the freeze-thaw impact on bed load transport over uniform and non-uniform sediment beds in the present study, the first series focused on the bed load transport under freeze-thaw-free and normal room temperature (20 ℃) condition, and this series is designated as benchmark tests, against which the impact of freeze-thaw action on bedload transport rate and composition can be examined, the second series are the group of comparative experimental tests, within which both uniform and non-uniform sediment beds were worked by sequential events of freeze, thaw, and steady flow at normal room temperature (20 ℃).Our experiments show that bed load transport rates are usually higher for both uniform and non-uniform sediment beds affected by freeze-thaw process if compared with measurements in benchmark tests, accordingly, a ratio ζ of bedload rates measured within freeze-thaw-impacted sediment bed over their equivalents obtained from freeze-thaw-free bed.A comparison between the ratio ζ and normalized shear stress indicates that the ratio ζ is higher (i.e.ζ>1.0) at lower normalized shear stress and gradually reduced (i.e.ζ→1.0) as normalized shear stress increased.For comparative tests using non-uniform sediment bed, the impact of freeze-thaw action on transported grain size is significant at low flows and gradually attenuated by increasing flow magnitude.These findings are important for enhancing our understanding of alluvial bed stability and evolution in cold regions. |
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