g
N
g
b
= 9.7 kN/m
3
= 21 (entering Fig. 6.5 with f′=32°, and intersecting the N
g
curve, the value of N
from
the vertical axis is equal to 21)
B = 1.5 m for the strip footings and 2.5 m for the spread footings
r
u
= 0.20 (entering Fig. 4.25 with a factor of safety against liquefaction = 1.3, the value of
r
= 0.20)
u
for sand varies from 0.05 to 0.35. Using an average value, r
u
g