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Casing shall be utilized for drilling through unstable soil formations
[and] [_____]. The casing shall be advanced by [rotary drilling] [or]
[driving].
[3.2.5
Drilling in Rock
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NOTE: Core drilling is more expensive and slower
than other drilling methods and should be specified
only where excessive vibration could endanger
existing structures or would otherwise be
objectionable, where it is expected that embedded
items will be encountered in an existing structure,
or as otherwise determined by the designer to be
necessary. Anchor holes which are core drilled may
require overdrilling with a roller bit or other
approved means to roughen the circumference of the
hole to promote bond with the grout. Where existing
foundation information is not complete, e.g. when
anchoring existing structures, it may be advisable
to require core drilling for initial (demonstration
test) anchor holes in each area to determine the
nature of the rock material and permit determination
of actual hole depths. If sufficient foundation
information cannot be provided to permit the
contractor to estimate design and installation of
the anchors prior to bidding, the prescriptive
tailoring option should be used.
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Unless otherwise specified, holesHoles in rock may be drilled by core
drilling, rotary drilling, percussion drilling or down-the-hole hammer
using equipment suitable for the intended purpose. [The drilling method
shall not cause structural damage to existing structures. If damage is
observed, the drilling method shall be modified.][Core drilling shall be
performed with rotary drilling equipment using diamond-matrix coring bits.]
[Core from holes shall be furnished to the Contracting Officer in core
boxes at the site for information. Additional drilling may be required
based on the quality of the rock encountered. Rock core from demonstration
test anchor holes only shall be retained by the Contractor for the duration
of the contract as specified in paragraph "Retention of Core". Retention
of core from other holes, after evaluation and release by the Contracting
Officer, is not required.] Overdrilling of holes by a maximum of one meter
three feet beyond the required elevation will be permitted if complete
removal of cuttings and other material cannot be accomplished. If the hole
is overdrilled, the tendon must be supported so that the free length
corrosion protection extends the required length into the trumpet and so
that the anchor can be stressed.
]3.2.6
Records
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NOTE: If core recovery and logging is required to
verify design assumptions or to provide additional
foundation information, Section 02210 SUBSURFACE
DRILLING, SAMPLING, AND TESTING should be included
in the project, or applicable portions should be
SECTION 02490
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