The Effect of Measurement Method, Size and Shape of Box in Sliding Method on the Angle of Repose of Soil Particles

The angle of repose of soil particles is an important factor for determining critical shear stress for initiation of soil particles motion during the erosion process. There are different methods for measuring the angle of particle repose and the result of each method is somewhat different from those of the others. Sliding and fixed-base piling methods are the two most common methods in the literature. In this study, 6 different size classes of a soil and a fluvial sand samples were subjected to the measurement of angle of particle repose using sliding and fixed-base piling methods. Sliding method was performed using 11 boxes of different sizes and shapes. Statistical analysis indicated that the effect of box size was significant (P<0.001) on the measured angle of particle repose. Increasing box width and depth resulted in higher values for the angle of repose, but increasing the box length has resulted in lower values for it. It seems that the increasing of the ratio of particle weight (amount) to the box cross section, leads to a decrease in AOR. The shape of box significantly affected the angle of particle repose (P<0.001). The comparison of the two methods indicated that the angle of particle repose measured by the fixed-base pilling method is about 10 degrees less than that of the sliding method. According to the results, the current methods for measuring the angle of particle repose seems to have shortcomings and there is a need to revise the measuring methods.