TM 5-818-4/AFM 88-5, Chap. 5
The inspection personnel must be thoroughly familiar
(a) The thickness of loose lifts can be checked
with every aspect of the earthwork section of the
easily by probing with a calibrated rod just prior to
specifications and know boundary locations for the
compaction. Compaction of lifts too thick for the
various zones of material. They should be able to read-
equipment will not normally be detected by perform-
ily identify the various classes of backfill and know
ing density tests on the lift, since adequate compaction
their compaction characteristics and requirements.
may be indicated by a test made in the upper portion
Good inspection personnel will also know the compac-
of the lift and the lower portion may still have too low
tion capabilities of various types of equipment and the
a density. It is therefore a requisite that lift thickness
materials that each type is best suited to compact.
be controlled on a loos&thickness basis prior to com-
(1) To maintain adequate control of compaction
paction
operations, a staff of earthwork inspectors and labora-
(b) Checks for proper bond between layers can
tory personnel commensurate with the importance of
be made by digging through a lift after compaction
the work and size of the operation is essential. There
and using a shovel to check this bond. If the soil can be
should be at least one inspector at the fill when back-
separated easily along the plane between lifts, suffi-
fill is being placed. His sole duty should be inspection
cient bond is not being provided. Backfill materials
of earthwork. Although he should be familiar with the
should not be placed on dried or smooth surfaces, as
testing procedures and capable of directing testing op-
bond will be difficult to obtain.
erations and selecting locations for testing, he should
(c) Inspection personnel should be thoroughly
not be required to perform the tests. Laboratory tech-
aware of areas where compaction is critical. These
nicians should be available for this purpose. A discus-
areas are the confined spaces around and adjacent to
sion of the methods and procedures for field density
structures that are not accessible to the rolling and
testing of the compacted fill is contained in section
spreading equipment. Although the volume of backfill
B-3, appendix B.
is usually rather small in these areas, a much higher
frequency of check testing for density is required as
(2) The specifications should require that neces-
well as a careful check of the quality and water content
sary processing of backfill materials be performed in
of the materials to be placed.
the stockpile or borrow pit. Processing includes raking
or crushing to remove oversize material, mixing to pro-
c. Compaction control tests. Compaction tests will
vide uniformity, and watering or aerating to attain a
have been performed on representative specimens ob-
water content approximating optimum for compac-
tained from exploratory sampling prior to construc-
tion. An earthwork inspector is required at the stock-
tion. The selection of suitable backfill material are in
pile or borrow pit to enforce these provisions. In addi-
fact generally made based on these and other tests. At
tion, this inspector has the duties of classifying the
least during the early phases of the backfill operation,
materials, determining their suitability, and directing
density requirements are based on these and in some
the zone of backfill in which they are to be placed. He
cases additional preconstruction compaction tests.
is charged with the responsibility of seeing that the
Conditions may develop that require compaction tests
contractor uses the materials available for backfill in
during backfill operations to establish new density re-
the most advantageous manner. Generally, the stock-
quirements. Generally, these changes are the results of
pile or borrow pit inspector relies upon visual inspec-
backfill material deviations. The need for additional
tion and experience to exercise control over these oper-
control tests may be ascertained from visual observa-
ations. Occasionally, he may require that appropriate
tion and changes in compaction characteristics during
tests be performed to confirm his judgment.
field compaction. For most backfill materials, quality
(3) The duties of the backfill inspector consist of
acceptance compaction control tests must be per-
checking the material for suitability as it is placed on
formed according to the CE 55 test procedure specified
the fill and spread, ensuring that any oversize mate-
in MIL-STD-621, the equivalent procedure in ASTM
rial, roots, or trash found in the material is removed,
D 1557, or the two-point test procedure (app B). For
checking the thickness of the lift prior to compaction,
some cohesionless soils where higher maximum dry
checking for uniformity and amount of water content,
densities can be obtained using the vibratory (relative
observing compaction operations, and directing or
density) compaction procedure, the specifications may
monitoring testing of the compacted material for com-
require the vibratory test procedures as specified in
pliance with density and water content requirements.
EM 1110-2-1906 or ASTM D 2049. Field compaction
(4) There are many techniques and rule-of-thumb
control and rapid compaction check tests that are used
procedures that the earthwork inspector can and must
to supplement the Corps acceptance control tests are
resort to for assistance in his work. A few of them are
discussed in appendix B.
discussed below; others can be ascertained by inspec-
tors meeting together to discuss problems and correc-
d. Field moisture-density control techniques. Mois-
tive action.
ture-density control is the most important phase of
7-4
Previous Page
