Determination of the size of representative volume element for gap-graded granular materials

Gap-graded granular soils have a wider grain size distribution and more heterogeneous fabric structure than normal soils. It is critical to choose the sample size of element tests in a faithful and repeatable manner. The Discrete Element Method (DEM) is utilized to determine the size of representative volume element (RVE) of gap-graded mixtures with varying particle size distributions. Over seven hundred triaxial tests are performed to investigate the effect of particle size ratio and coarse fraction on the typical RVE size. Microscopic parameters are analyzed to validate the reproducibility of the determined RVE sizes. The optimal RVE size is negatively proportional to particle size ratio and positively correlated with the coarse fraction. Empirical equations are further established to correlate the RVE sizes with particle size ratios for different coarse fractions. The findings may provide a useful reference for experimental and numerical studies in choosing the RVE size for gap-graded soils. [Display omitted] •Over seven hundred simulations are performed on gap-graded granular soils.•The Chi-square test is adopted to recommend the RVE sizes for each gradings.•The proper RVE size decreases with particle size ratio and increases with coarse fraction.•Empirical equations are proposed for the RVE sizes of gap-graded soils.