Experimental evaluation of procedural parameters affecting minimum density determination of low-fines poorly graded sands

Soil behaviour is influenced by particle packing, with minimum density defining the loosest reference state of sands. However, its determination is procedure-dependent, resulting in variability among existing methods. This study investigates the effects of deposition technique, funnel spout diameter, and mould dimensions on the minimum density of three low-fines poorly graded sands and proposes an alternative configuration. Thirty-three configurations based on IS 2720 (Part 14), ASTM D4254 Method C, JIS A 1224, Lade’s, and the proposed method were examined. Deposition technique had the greatest influence: zero free fall height (ZFFH) produced minimum densities 0.07 to 0.16 g/cc lower than spiral motion under otherwise identical conditions. It also achieved coefficients of variation below 1%, whereas inversion-based methods reached 3.14%. Spout diameter had a minor effect, with mean differences of 0.00 to 0.03 g/cc. The alternative mould improved repeatability under ZFFH and provided a small-scale configuration for the investigated sands.