沙的摩擦性质是影响沙丘形态的重要因素之一,研究沙土内摩擦角对于探讨床面沙波形态、沙丘流动性、沙丘稳定性、沙丘防护等都具有实际意义。本文实验研究了内摩擦角与粒径、含水率及天然坡角的定量关系。结果表明:当粒径从<0.125 mm增大到0.315~0.4 mm时,内摩擦角从32.25°减小到28.06°; 而粒径从0.315~0.4 mm增大到0.63~0.8 mm时,内摩擦角却从28.06°增大到31.47°。主要原因是,粒径小时颗粒的比表面积大,颗粒间接触面积大使得内摩擦角大。粒径大时,颗粒表面棱角突出,颗粒间嵌入咬合作用明显使得内摩擦角大。当含水率从0%增加到15%时,内摩擦角从29.07°增大到31.84°; 而含水率从15%增加到20%时,内摩擦角却从31.84°减小到30.75°。主要原因是一定含水率下沙土表现出黏聚性,而高含水率下水的润滑作用使得颗粒间摩擦力减小。内摩擦角与天然坡角都反映沙土摩擦特性,两者相等。
The sand particle friction property is one of the most important factors affecting the morphology of sand dunes. It has practical significance to discuss the bed morphology, the mobility, the stability and the protection of sand dunes. In this paper, we did some experiments to explore the quantitative relationship between internal friction angle and particle size, water content and slope angle. The results showed that when the particle size varied from <0.125 mm to 0.315-0.4 mm, the sand particle internal friction angle decreased from 32.25 to 28.06. When the sand particle size varied from 0.315-0.4 mm to 0.63-0.8 mm, the sand particle internal friction angle increased from 28.06 to 31.47. Smaller particles have larger surface which makes the contact area between particles larger. Larger particles have obvious effect of interlock function due to their rough surface. When the water content varied from 0 to 15%, the sand particle internal friction angle increased from 29.07 to31.84. When the water content varied from 15% to 20%, the sand particle internal friction angle decreased from 31.84 to 30.75. Water makes sands show some cohesion which makes the internal friction angle larger, but lubrication weaken the friction between particles when high water content. The internal friction angle and the slope angle are natural reactions of sand particle friction characteristic. The maximum slope angle is equal to the internal friction angle.
[1] 刘建宝,王乃昂,程弘毅,等.沙丘沙休止角影响因素实验研究[J].中国沙漠,2010,30(4):758-762.
[2] 王涛,刘树林.中国干旱区绿洲化、荒漠化调控区划[J].中国沙漠,2013,33(4):959-966
[3] 张伟民.金字塔沙丘粒度变化及表面过程的初步研究[J].中国沙漠,2013,33(6):1615-1621.
[4] 韩庆杰,屈建军,廖空太,等.海岸湿沙表面风沙传输特征的风洞实验研究[J].中国沙漠,2012,32(6):1512-1521.
[5] 张克存,姚正毅,安志山,等.巴丹吉林沙漠及其毗邻地区降水特征及风沙环境分析[J].中国沙漠,2012,32(6):1507-1511.
[6] 刘清秉,项伟,Lehane B M,等.颗粒形状对砂土抗剪强度及桩端阻力影响机制试验研究[J].岩石力学与工程学报,2011,30(2):400-410.
[7] 刘海波,张丽华,林大超,等.直剪试验有效剪切面积动态变化的改进计算[J].沈阳建筑大学学报(自然科学版),2010,26(3):503-504.
[8] 雷胜友.毛细水对潮湿粉细砂强度影响的理论分析[J].长安大学学报,2013,33(5):1-6.
[9] 任平第,陈光雄,周仲荣.不同水介质润滑下GCr15钢的微动磨损特性[J].摩擦学学报,2003,23(4):331-335.
[10] 黄雄,林荃,陈静.土工击实试验中预估最优含水率的方法[J].水运工程,2009,(7):157-160.
[11] 强跃,赵明阶,林军志,等.静止土压力系数探究[J].岩土力学,2013,34(3):727-730.
[12] 孟震,杨文俊.泥沙颗粒水下休止角与内摩擦角差异化初步探索[J].泥沙研究,2012,(4):76-80.
[13] 刘建峰,徐进,高春玉.土的直剪试验缺陷探讨[J].四川水力发电,2005,24(1):56-59.