Abstract: In the numerical simulation of the discrete element method (DEM), the porosity field has been employed to observe the width of shear bands, which aids in understanding the relationship between shear band width and particle characteristics. The porosity field is obtained by measurement circles. However, the measurement circle radius is usually determined empirically, lacking theoretical and numerical simulation research. Therefore, a study was conducted to investigate the relationship between the accuracy of porosity measurement and the measurement circle radius. Furthermore, the “1/2 width estimation method” and “1/2 curvature extremum method” based on the porosity field were proposed and applied to measure the shear band width in direct shear and biaxial compression tests. The measurement results were compared with those obtained using the particle rotation method and grid method. The DEM numerical results show that the proposed methods are effective for measuring the shear band width in direct shear and biaxial compression tests. In the direct shear test, the shear band width gradually increases with the increase of particle size. Due to the asymmetry and non-uniformity of the specimen, the two shear band widths in the X-shaped shear band of the biaxial compression test are not equal, and the shear band widens gradually during the axial loading process.

Key words: discrete element method, shear band, measurement circle, porosity, measuring technique