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泥沙模型应正确复演原型河道演变特点和规律 ,模型沙的选择是起关键作用的。为此 ,通过室内土力学试验、物理化学性能分析、玻璃水槽试验和泥沙模型验证试验结合理论分析等方法 ,对粉煤灰模型沙进行了试验研究 ,取得了以下主要成果和结论。 (1 )采用光学显微镜和电镜观察成果分析了粉煤灰的细观结构和理化特性 ,明确了 d>0 .0 76 mm的粉煤灰分散性较好 ;(2 )用定量数值对比了粉煤灰干重度及土力学特性变化规律与天然泥沙的差异 ,阐述了选用凝聚力较低的粉煤灰粒径组作模型沙的机理 ;(3)粒径为 0 .0 2 7～ 0 .1 1 m m的粉煤灰模型沙的干重度和起动流速随时间增加有限 ,不致引起模型沙明显的板结和起动相似偏离 ;(4)南水北调中线穿黄泥沙模型验证试验表明 ,粉煤灰模型沙能够较好地满足模型试验要求 ,模型挟沙水流物理特性和运动规律与原型相似 ;(5 )采取控制干重度使模型沙不发生板结现象的方法 ,可解决类似模型试验问题
Sediment model should correctly reproduce the characteristics and laws of evolution of the prototype river. The selection of model sand plays a key role. To this end, through the laboratory soil mechanics test, physical and chemical performance analysis, glass tank test and sediment model validation test combined with theoretical analysis and other methods of fly ash model sand were studied and achieved the following main results and conclusions. (1) The microstructure and physical and chemical properties of fly ash were analyzed by light microscope and electron microscope. It was found that the dispersity of fly ash with d> 0.076 mm was better. (2) The variation of dry weight and soil mechanics characteristics of coal ash and the difference of natural sediment, and expounds the mechanism of choosing the fly ash particle size group with lower cohesion as the model sand. (3) The particle size is 0 .027 ~ 0. The dry weight and starting velocity of the 11 1 mm fly ash model sand increased little with time, which did not cause obvious deviation of the formation sand and start of the model sand. (4) The Yellow River sediment model verification test of midline of the South-to-North Water Diversion Project showed that the fly ash model Sand can better meet the requirements of the model test. The physical characteristics and movement patterns of sediment-laden flow in the model are similar to the prototype. (5) The method of controlling dry weight so that sand does not occur in the model sand can solve similar model test problems