饱和悬浮塑料砂流动特性的试验研究

发布时间：2019-01-22 16:08

【摘要】：饱和砂土在液化状态下呈现出非牛顿流体的特性,而常规动力试验要获得稳定的液化状态比较困难。采用塑料砂和相等密度的氯化钠溶液配制成了有效应力接近于0的饱和悬浮塑料砂试样,基于流体力学低雷诺数绕球流动理论并结合粒子成像测速(PIV)技术,开发了饱和悬浮塑料砂流动特性的试验装置。利用紧贴透明模型箱内壁的半球在饱和悬浮塑料砂中运动时塑料砂颗粒的运动来分析其流动特性,并通过拉力与速度的关系计算饱和塑料悬浮砂的表观黏度。试验结果表明,饱和塑料悬浮砂试样是剪切稀化非牛顿流体,可作为液化砂土的相似材料用于液化问题的研究。基于试验中的细观规律,提出了零速度线、剪切区、剪切角、剪切区高度等实用概念。研究表明,拖球速度对剪切角有重要影响,速度越大,剪切角也越大,相应剪切区也越大。剪切区高度反映了拖球运动方向的影响范围,提出拖球试验中应保持球体形心与边界之间的距离要大于6倍球体直径。分析了拖球试验中的孔洞产生机制,提出在拖球和拖管试验中,应降低拖球的运动速度,以符合低雷诺数绕球(管)流动的基本理论。
[Abstract]:Saturated sand presents the characteristics of non-Newtonian fluid in liquefaction state, but it is difficult to obtain stable liquefaction state by conventional dynamic test. A saturated suspension plastic sand sample with effective stress close to 0 was prepared by using plastic sand and sodium chloride solution of equal density. Based on the theory of low Reynolds number flow around the sphere in hydrodynamics and the particle imaging velocimetry (PIV) technique, An experimental device for the flow characteristics of saturated suspended plastic sand was developed. The flow characteristics of plastic sand particles in saturated suspended plastic sand are analyzed by using the movement of the hemispheres close to the inner wall of the transparent model box. The apparent viscosity of the saturated plastic suspended sand is calculated by the relationship between the tension and the velocity. The experimental results show that the saturated plastic suspended sand sample is a shear-thinning non-Newtonian fluid and can be used as a similar material for liquefaction study. Based on the mesoscopic law in the experiment, the practical concepts of zero velocity line, shear zone, shear angle and shear zone height are put forward. The results show that the velocity of the ball has an important effect on the shear angle, and the larger the velocity, the bigger the shear angle and the larger the shear zone. The height of the shear zone reflects the influence of the direction of the towing ball. It is suggested that the distance between the center of the ball shape and the boundary should be kept more than 6 times the diameter of the ball in the towing test. The mechanism of hole formation in towing ball test is analyzed. It is suggested that the velocity of towing ball should be reduced in order to accord with the basic theory of low Reynolds number flow around the ball (tube).
【作者单位】：河海大学岩土力学与堤坝工程教育部重点实验室;河海大学土木与交通学院;
【基金】：国家自然科学基金面上项目(No.51379067,No.51679072) 重点国际合作研究项目(No.51420102013) 教育部创新团队发展计划(No.IRT_15R17)~~
【分类号】：TU441

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