3.4.4
Concrete Coring
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NOTES: The number of the test panels to be cored
should be determined by each district office as
necessary to give a representation of the work that
was done. The core boring of these test panels
should be done after the concrete has developed
sufficient strength to allow cores of properly
placed concrete to be retrieved.
The spacing and timing of the core borings of the
concrete cutoff wall should be arranged to retrieve
properly placed concrete cores. The concrete should
be allowed to develop sufficient strength to allow
cores of competent concrete to be retrieved. The
spacing of the core holes should be representative
of the particular job to give confidence in the work
that was performed. The wall construction should
not be allowed to get too far ahead of the core
boring. This will allow problems discovered by the
core boring to be corrected or changed and these
changes incorporated in the cutoff wall construction
that follows.
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3.4.4.1
Concrete Coring in Completed Panels
One NX core boring (or one core boring approximately NX) shall be drilled
through the concrete in each of the first [_____] test panels. These
borings shall be completed during the installation of the first [_____]
linear meters feet of cutoff wall and prior to commencement of the
remainder of the wall. Thereafter, an NX boring shall be drilled through
one panel selected by the Contracting Officer for every [_____] linear
meters feet of wall, within [_____] days after completion of each [_____]
meter foot section. Additional core borings may be directed by the
Contracting Officer. The borings shall be located in the center of each
panel unless otherwise directed by the Contracting Officer. While coring
the completed panels, the Contractor shall prepare a log including the
elevation of any drill fluid loss, soft zones, drill tool drops, or zones
of core loss and provide the log to the Contracting Officer immediately
after coring is complete. The core holes shall not be backfilled until
approved by the Contracting Officer. [If the Contracting Officer decides
to have falling head permeability tests or other tests conducted due to
core results, this shall not be used as basis for a claim.] Core holes
deviating through the side of the panel shall be filled and a new core hole
drilled at no additional cost to the Government.
3.4.4.2
Method of Drilling
Drilling of cores shall be by any approved standard and accepted method of
rotary rock core wireline drilling using diamond-set coring bits by means
of which continuous and complete cores of standard diameter for the
specified bit size shall be obtained.
3.4.4.3
Equipment and Supplies
Equipment to be furnished by the Contractor for core drilling shall include
SECTION 03373
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