of it which displaced the underlying soil to the sides. As the surrounding 
soil offers resistance to this movement, the displaced soil is forced upward. 
Shear takes place along the upwardly curving surface, which is much larger 
than the contact area between the load and the soil. It can be shown that 
the ultimate bearing capacity of the soil, U, is a function of the cohesion, 
the length and breadth of the load contact area and the depth to which the 
load sinks below the soil surface (Peck, Hanson, and Thornburn, 1953). For 
example, for a track whose length-to-width ratio is 5, in soft clay where 
s=c, and at a depth of 1 foot below the soil surface, 
U = 5.7¢c 
For ocean-bottom red clay at a depth of 1 foot below the soil surface where 
the shear strength is 0.043 psi, the ultimate bearing capacity for that track 
would be 
U7 axe O:043_— sO s25)psi 
rae: load 
we 
a, 
Figure 30. Soil shear path resulting from unconfined compression. 
38 
