Surface Control Instrumentation. Control instrumentation is placed 

 in an 8-foot wide by 12-foot long instrument van for protection. The 

 control instrumentation (Figure 3) is used to regulate the elements 

 attached to the platform, to permit a visual observation of the perform- 

 ance of the elements, and to present a permanent record of the subsystem 

 feedback. A 40-channel Pulse Duration Modulation (PDM) system provides 

 for the down-link control of the platform elements and the subsystem(s) . 

 A 20-channel digital PDM up-link control system gives positive readouts 

 at the control console of the condition of the submerged components. 

 In addition to the digital PDM control and readout system, an Inter- 

 Range Instrumentation Group (IRIG) FM carrier system was provided to 

 permit 14 channels of underwater transducer feedback to be recorded; 

 however, only four channels of data were used for the vane shear and 

 cone penetrometer tests; i.e., axial load, vertical displacement, torque 

 and rotation, as appropriate. 



Vane Shear and Cone Penetrometer Subsystem 



Description of the Tower . The vane shear and cone penetrometer 

 tower (Figure 2) is mounted on the DOTIPOS platform as an accessory, 

 and it is remotely controlled from the surface instrument van. The 

 2-inch diameter penetration rod is mechanically pressed into the soil 

 by an electrical motor and jack-screw system. The penetration rod is 

 inserted or withdrawn at a rate of 10 inches per minute. Another 

 electrical motor and transmission system is used to rotate the penetra- 

 tion rod at a rate of either 10 rpm or 1 rph (6 deg/min) . 

 Potentiometers are used to monitor both displacement and rotation of 

 the penetration rod. 



Load Cell . A load cell (Figure 4) is coupled to the bottom of 

 the tower penetration rod so that torque and axial load may be recorded 

 for the field vane and cone penetrometer. The load cell was designed 

 to measure a torque of to 500 in. -lbs and an axial force of to 

 2,000 lbs. It consists of an enclosed 1/2-inch diameter steel rod which 

 is instrumented with strain gages. Two single gages were placed along 

 the axis of the rod to measure axial load, and two 90-degree rosettes 

 were placed on the rod at 45 degrees to measure torque. Additional 

 gages were added for temperature compensation. 



Vane Shear and Cone Penetrometer Tools. Either a vane shear tool 

 or a cone penetrometer tool may be attached to the load cell. A drawing 

 of each tool and significant dimensions are presented in Figure 5. All 

 of the tools were fabricated from stainless steel. 



The shear vane consists of four thin rectangular blades which are 

 welded at 90 degrees to a circular shaft. A height-to-diameter ratio 

 of 2.0 was used for all four vanes. The four vane diameters are 2, 

 2^5, 3, and 4 inches. 



