Hardness Evaluation of Gravel-type Sediment Environments Based on Circularity and Friction Coefficient

Abstract

The influence of the shape of gravel on sediment hardness was discussed from the relationship between circularity degree and friction coefficient which can be easily measured. Calculation of circularity was based on the measurement with 30 grains per sample and considered to be sufficiently accurate. The decrease in circularity due to the change in the gravel shape corresponded well to the increase in the friction coefficient calculated from the angle of repose. In addition, the measured values of vane shear resistance, which is an index of sediment hardness, showed marked fluctuations that are consistent with the increase in friction coefficient due to the decrease in circularity. These results indicate that the circularity of gravel and associated variation in the friction coefficient can be utilized to infer the vane shear resistance, which is known to serve as a burrowing capability indicator for diverse benthic organisms.