Besides the plate load test, the subgrade modulus can also be obtained from Fig. 7.7. The values of
Kv
from Fig. 7.7 apply to dry or moist cohesionless (granular) soil with the groundwater table at a depth
of at least 1.5 B below the bottom of the footing. If a groundwater table is at the base of the footing,
then
1
/
2Kv
should be used in computing the settlement. For continuous footings, the settlement calcu-lated earlier should be multiplied by a factor of 2. The relative density Dr
can be estimated from the
standard penetration test Nvalue (see Table 2.6). Equations 7.5 to 7.8 may underestimate the settlement
in cases of large footings where soil deformation properties vary significantly with depth or where the
thickness of granular soil is only a fraction of the width of the loaded area.