As indicated by the above examples, the ultimate bearing capacity of plastic soil is often much less
than the ultimate bearing capacity of cohesionless soil. This is the reason that building codes (such as
Table 18.4) allow higher allowable bearing pressures for cohesionless soil (such as sand) than plastic
soil (such as clay). Also, because the ultimate bearing capacity does not increase with footing width
for saturated plastic soils, there is often no increase allowed for an increase in footing width.