The suggestion that increasing ∆P disrupts force chains may also explain the somewhat counter-intuitive results in Table . That is, increasing φ by an order of magnitude increases the number of clogs N by a factor of 2 -5. However, ∆P has a much weaker effect: increasing ∆P by an order of magnitude increases N by barely 50%. This less dramatic increase may be due to the disruption of force chains. Increasing ∆P certainly sends more particles into the channels, as seen in Table , but these do not all form new clogs. Consequently, N does not increase as strongly with ∆P compared to φ . In addition, increasing φ may somewhat reduce the ability of high ∆P to prevent clog formation. When ∆P is high and φ is low, clog prevention occurs very effectively upstream: the longest clogs are found downstream, where x < 1 cm, as seen in Fig. . However, as φ increases, the longest clogs are upstream, near x = 3 cm, towards the channel inlet area.