diamond core-drilling machinery of a type or types approved by the
Contracting Officer, complete with all accessories for taking continuous
cores of a diameter consistent with specified bit size to the depths
specified. The core drill shall be the product of one of the standard core
drill manufacturing companies designed primarily for this type of work.
The Contractor shall use a ball-bearing, swivel-type, double-tube NX core
barrel or manufacturers' equivalent meeting standards established by DCDMA
TM. Capacity of barrels shall not exceed 4.6 m 15 feet of core, and they
shall be equipped with diamond-set core bits and standard core lifters.
Supplies for core drilling to be furnished by the Contractor shall include
all casing, drill rods, core barrels, diamond-set coring bits, piping,
pumps, water, tools, core boxes, and power required for drilling. Bits
shall be set with the proper size stones for drilling the concrete and bed
rock.
3.4.4.4
Core Boxes
Longitudinally partitioned wooden core boxes constructed of dressed lumber
or other approved materials in general accordance with arrangement and
dimensions shown in the drawing included at the end of this section of the
specifications shall be used for all cores. As many core boxes as may be
required shall be used in submitting each concrete or rock core or group of
cores. Core boxes shall be completely equipped with all necessary
partitions, covers, hinges, and hasps for holding down the cover. To
prevent undue core breakage (while it is being placed in boxes) and to
allow for ease of access to core in the specified core boxes, the maximum
amount of core to be placed in any one box shall be determined by the
it is expected that an average of approximately 3.7 m 12 feet of core can
be placed in each box. In addition to the spacer blocks shown in the
drawing, the Contractor shall provide, as required, lengths of 29 by 54 mm
1-1/8 by 2-1/8 inch wood, painted red on one side, which shall be cut into
100 mm 4-inch lengths, marked with appropriate depths, and inserted in the
proper positions in core boring samples to show the location and actual
extent of voids and core losses. The Contractor shall mark all core boxes
with the appropriate hole number, box number, and depths.
3.4.4.5
Disposition of Core Samples
Upon completion of core drilling and sampling operations for each hole,
core boxes containing cores shall be delivered to a storage facility to be
designated at the project site. Core boxes containing cores shall be
delivered in accordance with schedules prepared by the Contracting Officer.
All packing, handling, and transportation of samples shall be considered
as subsidiary obligations of the Contractor.
3.4.4.6
Backfilling Core Holes
Upon completion of core sampling, the holes shall be backfilled under
gravity pressure with portland cement grout or mortar as directed by the
Contracting Officer. The grout shall be pumped into the hole through drill
rods or plastic hose set to within 1.5 m 5 feet of the bottom of the hole.
The bottom of the core hole is defined as being a point in bedrock 900 mm 3
feet below the bottom of the panel or the point at which the boring
deviates from the cutoff wall.
3.4.5
Evaluation and Acceptance
Concrete will be evaluated by examination of cores drilled by the
SECTION 03373
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