PART 3
EXECUTION
3.1
INSTALLATION
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NOTE: Caissons selected for contract shall be based
on analysis of subsurface investigation and design
requirements. Complete installation information
shall be provided to the Contracting Officer.
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3.1.1
Excavation
Drill caissons to depths and dimensions shown. [Excavate or drill the
bottom of excavations to bell diameters and shapes shown.] Drilling of
caisson shall not be within 6 m 20 feet of concrete placed within last 3
days. Clean bottoms of caissons of loose, soft, or disturbed materials and
level. Dispose of excavated material [in the area indicated] [off
Government property] [_____]. Excavations made below indicated depths,
without specific direction by the Contracting Officer, shall be filled with
concrete. Where, in the opinion of the Contracting Officer, materials are
encountered at the indicated depths that do not provide the required
bearing capacity or would result in unsatisfactory construction, the
excavation shall be extended as directed by the Contracting Officer and an
adjustment in the contract requirements will be made.
3.1.2
Protection and Casings
In drilling caissons, protect surrounding soil and excavated walls against
cave-ins, displacement of the surrounding earth, and retention of ground
water by means of temporary steel casings, sheeting, or use of bentonite
slurry. Casings shall not be driven within 6 m 20 feet of concrete placed
within last 3 days. If Contracting Officer determines that the structural
integrity of the caisson will be impaired, the casing shall be left in
place and an adjustment in the contract requirements will be made.
Withdraw temporary steel casings, as concrete is placed, maintaining
sufficient head of concrete within the casing to prevent extraneous
material from falling in from the sides and mixing with the concrete.
Casings may be jerked upward a maximum of 102 mm 4 inches to break the
bottom seal but thereafter removed with a smooth, continuous motion. All
voids surrounding the casing shall be filled with concrete extruded from
the bottom of the casing as it is being raised, with all free water
surrounding the casing being forced to the surface ahead of the rising
concrete. Provide venting if necessary to ensure removal of water around
the casing as the concrete level rises and the casing is being removed.
3.1.2.1
Cleaning Casings
Clean inside of steel casings thoroughly and oil before reuse.
3.1.2.2
Temporary Casings
The temporary casing shall be in place from the caisson top to the ground
surface until the concrete has set if the elevation of the top of the
caisson is below the adjacent ground surface.
3.1.2.3
Casings with Soft Subbase
Continuously remove water that flows into the excavations and the
SECTION 02468N
Page 9
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