Tensile strength of pebble piles, σ_pp, as a function of VFF, φ_pp. The box extending in VFF from 0.30 (Brisset et al. 2016) to 0.64 (random close packing RCP) and in strength from 0.4 Pa to 1.6 Pa stems from the data of Blum et al. (2014) and Brisset et al. (2016), rescaled to a pebble radius of 0.5 mm. The four curves show scaling laws σ ∝ φ^d, with d = 1 (Skorov & Blum 2012), d = 2 (Tatsuuma et al. 2019), d = 3, and d = 4 (Kreuzig et al. 2024). All four curves are forced to cross at φ_pp = 0.5. The data points show the results of the simulations with a scaling factor of 1/3 applied (see text for details) so that they also cross the four model curves at φ_pp = 0.5.