Determining the Dilatancy of Gravels Using a Large-size Direct Shear Test.

The peak shear strength of dense coarse-grained soils is defined by the angle of the shear strength, the initial shear strength, and the angle of dilatancy. This paper mainly focuses on determining the angle of dilatancy. This parameter has been investigated by many researchers on sands or sand-gravel mixtures. The study aims to determine the dilatancy angle of various types of gravel soils using a large-size direct shear test. The results demonstrated that the dilatancy angle decreases with an increase in the normal stress. The gravels tested were separated into 8 groups based on the type of gravel, the fraction, and the shape of the grains. The relation between the dilatancy angle and the normal stress was correlated using a power function for each gravel group. The results also showed that simplified assumptions of the dilatancy angle, which are usually applied in the design of geotechnical structures, can lead to a determination of a higher value of the dilatancy angle than that determined by laboratory measurement. A simple correlation is presented, which allows for determining the angle of dilatancy from the peak and the critical angle of the shear strength in a given normal stress range. [ABSTRACT FROM AUTHOR]