TM 5-818-1 / AFM 88-3, Chap. 7
coefficient of consolidation, cv, is shown in figure 3-7.
H = total thickness of compressible soil
the actual time required for the various
Other terms have been previously defined. Secondary
percentages of consolidation to occur in the field can be
compression settlements may be important where
determined by the following formula:
plastic or organic, and allowable settlements are
Settlement of cohesionless soils.
time for U(%) consolidation in the
permeability of cohesionless soils is usually sufficiently
construction period. For important projects, estimate
settlement using consolidation tests on undisturbed
time factor corresponding to U(%)
samples or samples remolded at natural density.
Alternately, settlements may be estimated from plate
bearing tests described in chapter 4. Design of footings
When settlement occurring during the construction
on cohesionless soils,
based on settlement
period may be of interest, the values of T and U also
considerations using the Standard Penetration Test, is
can be obtained from figure 5-5.
described in chapter 10.
c. Secondary compression.
Eliminating, reducing, or coping with
estimates and special purposes, settlement resulting
Design techniques for ameliorating
from secondary compression may have to be evaluated.
settlement problems are summarized in table 5-4.
The amount ∆Hs can be calculated as follows:
Differential settlements beneath existing structures can
be corrected by releveling by jacks, grouting (i.e., mud
jacking) beneath slab foundations, or underpinning.
These techniques are expensive, to varying degrees,
and require specialists.
tp + time interval during which
settlement is to be calculated