OCEAN-BOTTOM MINING TECHNOLOGY 405 



Conclusions and Recommendations 



1. The ability to observe actual operation of the air lift on the sea floor is very helpful. 



2. The greater the shear strength of the sediment, the higher must be the shoe inlet veloc- 

 ity. This points up the need to custom design shoes to suit the physical characteristics of bot- 

 tom sediments. 



3. Baffle plates are needed in the recovery tanks. Solids were lost through the recovery- 

 barrel overboard discharge even though 20 and 40 mesh screens were positioned in the lines 

 between the two recovery tanks. 



4. The "man handling" of one hundred or more feet of hose creates a considerable 

 problem. 



5. An oversupply of compressed air does not help sediment recovery. Excess air has an 

 adverse effect, in that it causes the recovery hose to thrash and whip. 



6. Manifolds two and three (Fig. 167) were tested, and each functioned relatively well. 

 Time limitations did not permit conclusive volumetric flow measurements. 



32-1/16 DIA. HOLES, 

 4 TO ROW, 8 ROWS 



64-1/8 DIA HOLES 

 8 TO a ROW, 8 ROWS 



32-1/8 DIA. HOLES 

 4 TO o ROW, 8 ROWS 



NO. I 



NO. 2 



T 



NO. 3 



NO. 4 



SCALE: 1/2"= l" 

 Fig. 167. Types of spools used on compressed air manifold 



ROTARY CORER EXPERIMENT 



General Description 



The rotary coring device (Fig. 168) is 14 ft high and weighs 1,000 pounds in air and 830 

 pounds in water. It is made up of off-the-shelf components assembled in a frame with tripod 

 legs to sit on the ocean floor and drill a six-foot core of sand, gravel, nodular material, or 

 rock. The unit is lowered and raised from a surface vessel, from which power is supplied to 

 a motor mounted on the device. The motor is controlled by an operating console on the surface 

 vessel. A circulating-water pump on the corer assists the core barrel in penetrating the dense 

 sands and gravels. The core barrel is lined with plastic sheet to facilitate core removal. 



