Investigation Methods and Procedures - Geotechnical Engineering Investigation - page 117

Air hoses
and
signal
cable

Air-operated
mechanical
vibrator

Core pipe

FIGURE 2.75
The Vibracore lowered to the seafloor.
(Courtesy of Alpine Ocean Seismic
Survey, Inc.)

Oriented core barrel contains knives that scribe a groove on the rock core. The
compass orientation of the groove is continuously recorded, which enables
determination of the strike of joints and other fractures ( Figure 2.83) . During nor-
mal coring operations cores twist in the hole and accurate determination of joint
strikes are not reliable.

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Coring Bits
General
Types of coring bits are based on the cutting material, i.e., sawtooth, carbide inserts, and
diamonds.
Waterways are required in the bits for cooling. Conventional waterways are passages cut into
the bit face; they result in enlarged hole diameter in soft rock. Bottom-discharge bits should be