TM 5-818-4/AFM 88-5, Chap. 5
in an enclosed space allocated by the project officer or
pects of backfill operation, such as selection and avail-
in mobile testing laboratories, such as pickup trucks
ability of materials, processing, hauling, compaction,
with a camper and equipped with the necessary testing
and inspection procedures. Some of the most common
equipment for performance of field density tests, wa-
deficiencies in inspection personnel activities are as
follows:
ter content tests, and gradation tests. Another possi-
bility is the use of large portable boxes in which equip-
(1) Failing to enforce specification requirements
ment is stored. When special problems arise and the
for preparation of the area for backfill. Often tempo-
rary fills, the working platform, debris, and other un-
required testing equipment is not available at the site
desirable materials are left in the excavation causing
laboratory, the testing should be performed at the cen-
tral laboratory.
weak areas and resulting in greater consolidation in
the backfill.
7-3. Excavation control techniques. Con-
(2) Failing to be cognizant of detailed site-adapted
trol to obtain a satisfactory excavation is exercised by
plans for stockpiling and placing backfill at specific lo-
enforcement of approved plans, visual observations, a
cations. Without knowledge of these plans, inspection
thorough knowledge of the contractor's plan of opera-
personnel are sometimes forced to make engineering
tion and construction schedule, the dimensions and en-
decisions beyond their capability, such as on-the-site
gineering features of the structure(s) to be placed in
approval of a new material or mixture of materials,
the excavation, and vertical and horizontal control
and stockpile locations.
measurements to ensure that the proper line and grade
(3) Allowing processing of backfill material and
requirements are met.
adjustment of water content on the fill that should
have been accomplished prior to placement. The re-
7-4. Foundation
preparation control
sults are the segregation of grain sizes and the nonuni-
techniques. The main control technique for ensur-
form distribution of water content. All major process-
ing proper foundation preparation is visual inspection.
ing, including crushing, raking, mixing, and adjusting
Prior to backfill placement, all uncompacted fill
of water content, must be done in the stockpile or bor-
should be removed from those portions of the excava-
row areas.
tion to be backfilled. The items included are road fills,
(4) Allowing lift thickness that is inconsistent
loose material that has fallen into overexcavated areas
with equipment capabilities and thicker than that al-
adjacent to foundations, and construction ramps other
lowed by specifications. Field density determinations
than those required for access to the excavation. Iden-
will not necessarily detect this inconsistency.
tification of such items will be easier if the inspection
(5) Allowing construction of backfill slopes that
personnel have charted the items on the plans as they
are too steep to obtain the full effect of compaction
were created, since they are not always easily discerni-
equipment.
ble by visual inspection. It is desirable to control earth
(6) Failing to require that the fill be built up uni-
backfill placed in foundation leveling operations by
formly in a well-defined pattern. Since the contractor's
water content and density tests. Care should be exer-
next move cannot be predicted, the inspection person-
cised to ensure that all subdrains required in the foun-
nel cannot adequately plan their operations, and it is
dation are protected by filters and transitional zones
difficult to determine which areas of backfill have
that are adequate to prevent infiltration of fines from
been tested and approved when the backfill is built up
the surrounding backfill that might otherwise clog the
in an unorganized manner.
drains and undermine structures.
(7) Allowing segregation of coarse-grained, nonco-
7-5. Backfill quality acceptance control.
hesive materials. This condition is caused by improper
The necessary authority to assure that compacted
hauling, dumping, and spreading techniques.
backfill is in compliance with the specifications is giv-
(8) Allowing the use of compaction equipment not
en in the specifications. The control consists of in-
suited to material being compacted.
specting and testing materials to be used, checking the
(9) Failing to perform sufficient field density test-
amount and uniformity of soil water content, main-
ing in critical areas.
taining the proper thickness of the lifts being placed,
(10) Allowing material that is too wet or too dry
and determining the dry unit weight being obtained by
to be compacted.
the compaction process. While control consists of all of
(11) Failing to require that intermediate backfill
these things, good inspection involves much more.
surfaces be shaped to drain during backfilling at other
locations.
a. Inspection activities. One of the best inducements
to proper placement and compaction of backfill is the
b. Inspection requirements. To properly control and
presence of the inspection personnel when backfill is
inspect backfill operations, the inspection personnel
being placed. However, to be of value the inspector
must keep informed of the construction schedule at all
must know his job. He should be familiar with all as-
times and be at the site where backfill is being placed.
7-3
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