抄録
A series of direct shear tests between sand and various kinds of smooth or lubricated surfaces was performed for a wide range of normal stress to quantitatively evaluate the shear resistance between them. The angles of friction between sand and hard surfaces of either Teflon or two kinds of glass platens or polished stainless steel platen were more or less similar and were not smaller than 5 degrees for a range of normal stress from 0.056 kgf/cm2 (5.5 kN/m2) to 1.6 kgf/cm2 (157 kN/m2) under the test condition employed. It was also found that at normal stresses higher than around 0.1 kgf/cm2 (10 kN/m2) the lubrication method by means of a thin latex rubber membrane and a silicone grease layer is much more effective than the methods using smoothed or polished hard platens. Furthermore, it was found that when the surface of Teflon sheet placed on a hard platen was rather flexible by the presence of the underlying soft material like grease the angle of friction becomes quite large due to the indentation of sand particles into the Teflon sheet.
