Transcript CONSOLIDATION OF SOILS and HYDROCOMPACTION

CONSOLIDATION
OF SOILS
and
HYDROCOMPACTION
J. David Rogers
Part 1
COMPACTION
and
PRIMARY
CONSOLIDATION

The Proctor Compaction Test employs a 5 lb weight
being dropped 18 inches repeatedly on a soil sample
of 1/30th of a cubic foot, in three lifts, or layers of soil.
The moisture content corresponding to the maximum
achievable dry density is termed the optimum
moisture content
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Soil moisture-density relationships are commonly
referred to as “compaction tests”
Note how soil density is a function of the compactive
energy; the more energy expended per unit volume
of soil, the greater the density and lower the water
content

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The Standard Proctor (ASTM D 698) test was
introduced in 1933 and employs 12,600 ft-lbs of input
energy per ft3 of soil
The Modified Proctor (ASTM D 1557) test was
introduced in 1957 and employs 56,200 ft-lbs of input
energy per ft3 of soil

Typical range of dry density versus moisture
content for various soil mixtures, as
determined by Standard Proctor compaction
tests

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Water is added or deleted from soil mixtures to effect
maximum achievable compaction
After placement, soil mixtures can be expected to
absorb additional moisture until equilibrium is
achieved, thereby lessened soil density

Differential settlement is a widespread and nagging
problem wherever fill has been placed to support
structures, such as highways. Improved compaction
helps to reduce settlement.
Primary Consolidation

Primary consolidation occurs when interstitial
pore water is squeezed out of saturated clay

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One dimensional consolidation, or odometer test (upper)
Traditional representation of primary consolidation tests (lower)

Primary consolidation exerts controlling influence on
soft soil sites. A number of options may be
employed to mitigate potential damage, listed above