2-inch pipe floor flange. A short nipple and a nominal 2- by 2- by 0./5- 
inch pipe tee are threaded to the floor flange to receive the core barrel. 
A nominal 0.75-inch check valve is installed in the side opening of the tee 
by way of an elbow which places the valve in a vertical position. The floor 
flange and all joints are sealed, which creates a vacuum in the core tube 
during retrieval and holds the cored sediments in place. 
2. Core Tube. 
Nominal 2-inch polyvinyl chloride (PVC) pipe was used as core tube because 
it is reasonably inexpensive, readily available, and acts as both core barrel 
and disposable liner. This size pipe is also easy to handle and is large 
enough in diameter to show internal sediment stratifications. Two wall thick- 
nesses of PVC were tested: SDR 26 (thin wall) and Schedule 40 (thick wall). 
These were tested with both blunt and sharpened ends. Of the two, the Sched- 
ule 40 with a sharpened end appeared to be the best. A pipe adapter can be 
used to thread the core tube to the floor flange, or in the case of the 
Schedule 40, the pipe can be threaded. No cutterhead or core retainer was 
used and in most cases the check valve was adequate to retain the core during 
recovery. 
3. Vibrator. 
The 3-inch vibrator used was a piston-type industrial vibrator model BH3 
Long-Stroke, Impacting, manufactured by the National Air Vibrator Company, 
Houston, Texas. The vibrator weighs 33 kilograms and consumes 14 standard 
cubic feet per minute at 50 pounds per square inch. A 0.3/7-inch hose was used 
to supply air at 60 pounds per square inch to the vibrator and a 1.5-inch 
exhaust hose was used to return the air to the surface. Similar vibrators 
are available from other commercial firms. A direct impact-type vibrator with 
a hole in the base plate opening to the piston chamber should not be used 
unless an adequate seal can be made between the base of the vibrator and the 
mounting plate. 
4, Field Operation. 
For field use the vibrator is connected by hose to a suitable size compres-— 
sor with a second hose of larger diameter connected to the exhaust port to 
exhaust the air above the water surface. The hoses should have sufficient 
wall strength to resist collapsing under the water pressure at normal coring 
depth. In order to keep air in the system at all times when the vibrator is 
underwater, an air valve is connected to the exhaust hose side. Pressure is 
thus kept in the system without activating the vibrator. If difficulty 
occurs in starting the vibrator underwater, vibration can be commenced before 
lowering. When the corer is on the bottom the lifting cable is slackened and 
coring commences. Vibration can be continued for a specified time (e.g., 10 
to 15 minutes was used during the tests) or a tag line connected to the slide 
section can be payed out as the core is driven to roughly indicate when 
penetration is stopped or near refusal is attained. After penetration the 
vibrator is stopped, then pullout and recovery are commenced. When the corer 
is retrieved the core tube is removed, any excess empty tubing cut off, the 
ends capped and sealed with tape, and the core tube marked to identify it and 
indicate top and bottom. 
