推移質泥沙的隨機起動規律研究

泥沙起動是河流泥沙動力學基本概念之一，對泥沙運動及河床沖淤變形研究有著重要意義。基於泥沙起動的隨機特性，採用二維床沙顆粒位置試驗，對隱蔽角和暴露角的分佈規律進行概率統計，表明二者服從相同的正態分佈。在顆粒位置試驗數據的基礎上，引入床沙有效暫態起動參數的概念，採用單顆粒泥沙起動模型，建立了反映顆粒隱蔽和暴露效應的床沙有效暫態無量綱起動切應力和起動流速公式。統計結果表明，床沙有效暫態無量綱起動切應力和起動流速均服從對數正態分佈；顆粒隱蔽效應顯著增大了二者的量值大小和離散程度，表明顆粒隱蔽效應增加了泥沙起動的難度和隨機性。在此基礎上，引入泥沙起動全概率的概念，構建了反映泥沙起動隨機特性的泥沙起動概率、起動切應力和起動流速公式。計算結果表明，泥沙起動臨界條件與泥沙起動標準存在一一對應關係，在實際應用中應依據泥沙起動標準的需要來選擇泥沙起動臨界條件。

關鍵字

推移質；隨機理論；起動概率；起動切應力；起動流速

並列摘要

Sediment incipient motion is one of the basic concepts of river sediment dynamics, which is of great significance to the study of sediment transport and bed deformation. Based on the stochastic characteristics of sediment initiation, a two-dimensional bed sand particle position test was used to perform probability statistics on the distribution laws of concealed and exposed angles, which showed that both obeyed the same normal distribution. Based on the experimental data of particle position, the concept of the effective instantaneous incipient parameter of bed material is introduced, and the formulas of effective instantaneous dimensionless incipient shear stress and incipient velocity of bed material, which reflect the hidden and exposed effects of particles, are established by using the single particle incipient model. The statistical results show that the effective instantaneous dimensionless incipient shear stress and incipient velocity of bed material obey the lognormal distribution. The particle concealment effect significantly increases the magnitude and dispersion degree of the two, indicating that the particle concealment effect increases the difficulty and randomness of sediment incipient motion. On this basis, the concept of total probability of sediment incipient motion is introduced, and the formulas of sediment incipient probability, incipient shear stress and incipient velocity, which reflect the random characteristics of sediment initiation, are constructed. The calculation results show that there is a one-to-one correspondence between the sediment incipient conditions and the sediment incipient criteria. In practical applications, sediment incipient conditions should be selected according to the needs of sediment incisive criteria.