颗粒形状对珊瑚砂和石英砂沉降影响的试验研究

在研究海岸侵蚀的过程中,泥沙沉速是一个重要参数,对于侵淤量的计算非常重要。近些年来,由于工程活动、海洋动力和气候等因素变化的影响,珊瑚砂海岸的侵蚀冲刷问题已不容忽视。考虑到珊瑚砂与石英砂在形状、比重上的不同会对其沉速造成影响,套用现有石英砂的沉速公式进行计算并不合适。本文针对珊瑚砂和石英砂进行沉降试验,分析形状对珊瑚砂沉速的影响。结果显示,在小粒径(d 0.5 mm)下形状对珊瑚砂沉速的影响并不明显,在大粒径(d 0.5 mm)下明显减缓了珊瑚砂的沉降速度,套用石英砂的沉降公式计算出的珊瑚砂沉速明显偏大。故通过提出动力形状因子这一参数来表征形状对沉降的影响,推导出考虑了形状影响的沉降公式,能够较为准确地计算砂粒的沉速范围,计算精度随着黏度的增大而提升。

Experimental study on the influence of particle shape on the settlement of coral sand and quartz sand

In the study of coastal erosion, the sedimentation rate is an important parameter for the calculation of the amount of silt intrusion. In recent years, the erosion and scouring of coral sand coast cannot be ignored due to the influence of engineering activities, ocean dynamics and climate and other factors changes. Considering that the difference in shape and specific gravity between coral sand and quartz sand will affect their sinking velocity, it is not appropriate to apply the existing formula of sinking velocity of quartz sand for calculation. In this paper, the sinking test was conducted for coral sand and quartz sand to analyze the effect of shape on the sinking velocity of both sands. The results show that the effect of shape on the settling velocity of coral sand is not obvious at small particle size (d < 0.5 mm), and it is obvious that the settling velocity of coral sand is slowed down at large particle size (d > 0.5 mm), and the settling velocity of coral sand calculated by applying the settling equation of quartz sand is obviously large. Therefore, by proposing the parameter of dynamic shape factor to characterize the influence of shape on settling, the settling equation considering the influence of shape is derived, which can estimate the range of settling velocity of sand grains more accurately, and the calculation accuracy is improved with the increase of viscosity.