師哲　龍超平　嚴軍

摘要：泥沙模型應正確復演原型河道演變特點和規律，模型沙的選擇是起關鍵作用的。為此，通過室內土力學試驗、物理化學性能分析、玻璃水槽試驗和泥沙模型驗證試驗結合理論分析等方法，對粉煤灰模型沙進行了試驗研究，取得了以下主要成果和結論。(1)采用光學顯微鏡和電鏡觀察成果分析了粉煤灰的細觀結構和理化特性，明確了d＞0.076 mm的粉煤灰分散性較好；(2)用定量數值對比了粉煤灰干重度及土力學特性變化規律與天然泥沙的差異，闡述了選用凝聚力較低的粉煤灰粒徑組作模型沙的機理；(3)粒徑為0.027～0.11 mm的粉煤灰模型沙的干重度和起動流速隨時間增加有限，不致引起模型沙明顯的板結和起動相似偏離；(4)南水北調中線穿黃泥沙模型驗證試驗表明，粉煤灰模型沙能夠較好地滿足模型試驗要求，模型挾沙水流物理特性和運動規律與原型相似；(5)采取控制干重度使模型沙不發生板結現象的方法，可解決類似模型試驗問題。
關鍵詞：粉煤灰； 高含沙； 沖淤相似
分類號：TV141　　　文獻標識碼：A
文章編號：1001-5485(2000)03-0014-05

Investigation of flyash model sands

SHI Zhe, LONG Chao-ping, YAN Jun
(Yangtze River Scientific Research Institute, Wuhan 430010,China)

Abstract：Because sediment model is required to correctly replicate the characteristics and regularity of river bed evolution in prototype,the selection of model sands plays the role of key.For this purpose,by means of the methods of laboratorial soil mechanics tests,the analyses of physical-chemistry properties, combining the experiment results obtained in the glass flume and sediment model tests with theory analysis ,etc.,the tests for flyash model sands were carried out.The primary results and conclusions are as following：(1)The results on the fine structure and physical-chemistry properties of flyash were obtained and analysed using the optical microscope and eletronic microscope,it was demonstrated that the decentralization property of flyash with partical size d＞0.076mm is better;(2)Through contrasting the differences in values between flyash and nature sands in their dry unit weight and soil mechanic characteristic variation,the mechanism of selecting flyash partical size groups,in which cohesion is rather low,as model sands is represented;(3)The increase of the dry unit weight and the incipient velocity of flyash with time(partical size ranges from 0.027 mm to 0.11mm)is very small so as to not generate obvious consolidation effect and similarity departure;(4)The results obtained from sediment model tests for Diversion Project from South to North China crosscut the Yellow River showed that the flyash model sands can meet the requirements of model test well,and the physical properties and regularity of silt-carrying flow on model are silimar to prototype;(5)Employing the method of controlling dry unit weight to keep model sands not generate consolidation phenomenon,this kind of model sands may solve the problems of analogic model test.
Key words： flyash; high silt-carrying flow; similarity of scouring and silting