Figure 2. Experimental data points and theoretical prediction of the maximum height of sandcastle as a function of its radius.

The solid line is the theory without any adjustable parameters using G = 0.054 a^−1/3E^2/3γ^1/3, where a = 100 µm, E = 30 GPa, γ = 70 mN/m. The density of the sand is ρ = 2.6 g/cm³. The small but systematic discrepancy between the theory and the experiments is likely to be due to perturbations that arise when we remove the PVC pipes, leading to a somewhat smaller maximum height than the theoretical one.