The effects of soluble salts on the threshold shear velocity of fine sand



Wind tunnel tests were carried out to investigate the effects of two soluble salts (NaCl and KCI) on the threshold shear velocity of a well-sorted, fine sand. A sensitive laser monitoring system was used to detect initial grain motion during the tests. Results indicate that even small amounts of soluble salt can significantly increase the threshold velocity of the sand because of cement-like bonds formed between grains that tend to hold individual particles in place. However, with increasing concentration the salt crystal growth causes the initially smooth sand surface to develop an irregular frothy texture which also directly affects the threshold shear velocity. This is indicated by increased scatter of data on the threshold shear velocity-surface salt concentration plots for both NaCl and KCl. Although data scatter is evident, significant exponential relationships do exist between threshold shear velocity and surface salt concentration in each case.