Runaway evolution of midplane solid-to-gas ratios in the cases of Sil-RPU (left) and Ice-RPU (right). Blue and green lines represent midplane solid-to-gas ratio of pebbles and silicate grains, respectively. Time proceeds as dotted, dashed and solid lines. Left panel is the case of α_tur = 1 × 10⁻³, F_p/g = 0.3, α_acc = 1 × 10⁻² and K = 1. Right panel is the case of α_tur = 3 × 10⁻³, F_p/g = 0.5, α_acc = 1 × 10⁻² and K = 2.