Incipient Motion Mode and Incipient Velocity of Soil Erosion on Cohesionless Soil Slope

無粘性土質岸坡土體沖刷起動模式及起動流速研究

王力(LI WANG) ； 王世梅(SHIMEI WANG) ； 郭飛(FEI GUO)

《台灣水利》 69卷3期 (2021/09) Pp. 46-58

https://doi.org/10.6937/TWC.202109/PP_69(3).0006

摘要

The effect of rainfall or wave on the erosion of cohesionless soil slope is obvious, but at present, the study on the mechanism of soil incipient motion is insufficient, especially the incipient motion mode of soil particles has not been unified, which leads to a large gap between the estimated incipient motion velocity and has a great impact on the prevention and control work. Based on the state of the force on the particles in the cohesionless soil slope when they are scoured to move, the drag force equation and the corresponding calculation method of scouring velocity were constructed and verified. Based on PFC program of particle flow, a new method to determine the incipient motion mode of slope soil was proposed. The method was used to simulate the erosion motion of a cohesionless soil slope, and the corresponding incipient motion velocity of each incipient motion mode was obtained and compared. The results showed that the method of judging the incipient motion mode of slope soil based on particle flow program was reliable, and the incipient motion mode of slope soil depends on the velocity of water erosion. When the scour velocity is low, the mainly incipient motion mode is rolling, when the scour velocity increases to a certain value, the mainly incipient motion models is sliding. The gradient of slope has a greater influence on the critical speed of the rolling motion and a smaller influence on the critical speed of sliding motion mode.

關鍵字

Sediment incipient ； Scour ； Incipient motion velocity ； Incipient motion model

並列摘要

降雨或波浪作用對無黏性土坡的坡面沖刷效應明顯，但是目前對坡面土體起動機理研究不足，尤其是土顆粒的沖刷起動模式還沒有統一認識，導致估算的起動流速差距較大，對岸坡防治工作產生極大影響。基於無黏性土坡顆粒起動時的受力狀態，構建了導致顆粒產生滑動起動和滾動起動的坡面水流拖曳力方程以及相應的沖刷流速計算方法，並進行了驗證。基於顆粒流PFC程序提出一種判斷坡面土體起動模式的新方法，應用該方法對某無黏性土坡進行了沖刷起動模擬，獲得了各起動模式對應的起動流速，並進行了對比驗證。結果表明：基於顆粒流程序的坡面土體起動模式判斷方法可靠，岸坡土體的起動模式取決於水流沖刷速度，沖刷速度較低時以滾動起動為主，沖刷速度增大到某一值時，岸坡土體以滑動起動為主；岸坡坡度對滾動起動臨界速度影響較大，而對滑動起動的臨界速度影響較小。

並列關鍵字

泥沙起動 ； 沖刷 ； 起動流速 ； 起動模式