Table 1.

The key predictions from the five models; ✓: present, ✗: absent, ✓*: partially present.

model variant	excess of large grains ejected	small-grain lining	pit completion time	large-grain excess at bottom of trench during construction	small grains at nadir
central digging, no redistribution	✗	✓*	✗	✗	✗
central digging, no drag	✓*	✓*	800	✗	✗
central digging with drag	✓*	✓	500	✗	✓*
spiral digging r = 25, with drag	✓	✓	300	✓	✓
spiral digging r = 50, with drag	✓	✓	600	✓	✓