TM 5-818-1 / AFM 88-3, Chap. 7
Table 5-1. Causes of Settlement
Cause
Comment
Compression of foundation
Soft, normally consolidated clays and
soils under static loads.
peaty soils are most compressible.
Loose silts, sands, and gravels are
also quite compressible.
Compression of soft clays
Increased effective stress causes
due to lowering ground-
settlement with no increase in sur-
water table.
face load.
Compression of cohesionless
Loose sands and gravels are most sus-
soils due to vibrations.
ceptible.Settlement can be caused by
machine vibrations, earthquakes, and
blasts.
Compression of foundation
Loose silty sands and gravels are most
soil due to wetting.
susceptible.Settlements can be
caused by rise in groundwater table
or by infiltration.
Shrinkage of cohesive soils
Highly plastic clays are most suscept-
caused by drying.
ible.Increase in temperature under
buildings containing ovens or fur-
naces may accelerate drying. Wetting
of highly plastic clays can cause
swelling and heave of foundations.
Loss of foundation support
Waterfront foundations must extend below
due to erosion.
maximum erosion depth.
Loss of foundation support
Most pronounced in soft, saturated clays.
due to excavation of
adjacent ground.
Loss of support due to
Lateral shifting may result from land-
lateral shifting of the
slides, slow downhill creep, or move-
adjacent ground
ment of retaining structures.
Loss of support due to
Soils overlying cavernous limestone and
formation of sinkhole.
broken conduits are susceptible.
Loss of support due to thaw-
Permafrost should be insulated from
ing of permafrost.foundation heat.
Loss of support due to
Loose, saturated sands are most
partial or complete
susceptible.
liquefaction.
Downdrag on piles driven
Loading on piles is increased by nega-
through soft clay.
tive skin friction if soil around
upper part of pile settles.
U. S. Army Corps of Engineers
5-2
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