TM 5-818-4/AFM 88-5, Chap. 5
quirements. Also, as the materials are placed in stock-
slopes. The slopes may be either unsupported or sup-
piles, water should be added or the materials should be
ported by shoring and bracing. The lines and grades in-
aerated as required to approximate optimum water
dicated in the plans should be strictly adhered to. The
content for compaction. Field laboratory personnel can
contractor may attempt to gain additional working
assist in determining the extent to which this is neces-
room in the bottom of the excavation by steepening
sary. The requirements of shaping the stockpile to
the slopes; this change in the plans must not be al-
drain and sealing it against the entrance of undesir-
lowed.
able water by rolling with spreading equipment or
(a) Where shoring and bracing are necessary to
covering with polyethylene sheeting should be en-
provide a stable excavation, and the plans and specifi-
forced. This step is particularly important for cohesive
cations do not provide details of these requirements,
soils that exhibit poor draining characteristics and
the contractor should be required to submit the plans
tend to remain wet if once saturated by rains. Stock-
in sufficient detail so that they can be easily followed
piles must be located over an area that is large enough
and their adequacy checked. The first principle of ex-
to permit processing and where they will not interfere
cavation stabilization, using shoring and bracing, is
with peripheral drainage around the excavation and
that the placing of supports should proceed with exca-
will not overload the slopes of the excavation.
vation. The excavation cut should not be allowed to
yield prior to placing of shoring and bracing since the
(b) In cases where significant energy and cost
saving can be realized, special stockpiling require-
lateral pressures to be supported would generally be
considerably greater after yield of the unshored cut
ments should be implemented. An example would be a
face than if no movement had occurred prior to place-
large project consisting of a number of excavation and
ment of the shoring. Excavation support systems are
backfilling operations. The excavation material from
discussed in TM 5-818-1/AFM 88-3, Chapter 7. All
the first excavation could be stockpiled for use as back-
fill in the last excavation. The material from the inter-
safety requirements for shoring and bracing as con-
tained in EM 385-1-1 should be strictly enforced.
mediate excavations could in turn be immediately used
(b) The inspector must be familiar with stockpil-
as backfill for the first, second, etc., phases of the proj-
ing requirements regarding the distance from the
ect and thereby eliminate double handing of excavated
crest of the excavation at which stockpiles can be es-
backfill for all but the first-phase excavation.
tablished and heavy equipment operated without en-
(5) Protection of exposed material. If materials
dangering the stability of the excavation slopes. He
that are exposed in areas, such as walls of a silo shaft,
must also know the maximum height of stockpile or
foundation support, or any other area against which
weight of equipment that can be allowed at this dis-
concrete will be placed, are susceptible to deterioration
tance.
or swell when exposed to the weather, they should be
(c) Excessive erosion of the excavation slopes
properly protected as soon after exposure as possible.
must not be permitted. In areas subject to heavy rain-
Depending on the material and protection require-
fall, it may be necessary to protect excavation slopes
ments, this protection may be pneumatic concrete, as-
with polyethylene sheeting, straw, silt fences, or by
phalt spray, or plastic membrane (TM 5-818-1/AFM
other means to prevent erosion. Excavation slopes for
88-33, Chap. 7). In the case of a foundation area, the
large projects that will be exposed for several seasons
contractor is required to underexcavate leaving a cover
should be vegetated and maintained to prevent ero-
for protection, as required, until immediately prior to
sion.
placement of the structure foundation. Any frost-sus-
(4) Stockpiling excavated material. Generally,
ceptible materials encountered during excavation
procedures for stockpiling are left to the discretion of
should be protected (para 2-3h (3) and (4)) if the exca-
the contractor. Prior to construction, the contractor
vation is to be left open during an extended period of
must submit his plans for stockpiling to the contract-
freezing weather.
ing officer for approval. In certain cases, such as where
(6) Excavation record. As the excavation pro-
there are different contractors for the excavation and
gresses, the project engineer should keep a daily record
the backfill phases, it may be necessary to include the
of the type of material excavated and the progress
details for stockpiling operations in the specifications.
made. This record would be of value if subsequent
In either case, it is important that the stockpiling pro-
claims of "Changed Conditions" are made by the con-
cedures be conducive to the most advantageous use of
tractor.
the excavated materials.
4-2. Foundation preparation.
(a) As the materials are excavated, they should
be separated into classes of backfill and stockpiled ac-
a. General. In this manual, preparation applies to
cordingly. Thus the inspection personnel controlling
foundations for backfill as well as those for structures
the excavation should be qualified to classify the mate-
to be placed in the excavation. Generally, if proper ex-
rial and should be thoroughly familiar with backfill re-
cavation procedures have been followed, very little ad-
4-2
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