Initial efforts toward providing an attitude sensor focused on a 

 standard pendulum-type device. The vibration of the anchor, however, 

 prevented this device from being successfully employed. A simple 

 solution to the problem was achieved by incorporating a mercury switch 

 into the displacement monitoring system's electrical circuit. This 

 switch is set so that when the tilt of the anchor exceeds a specified 

 angle, the pinger of the displacement monitor is turned off. This 

 essentially signals the shipboard monitor that the anchor is resting 

 at a precarious angle or that it has overturned. 



General Test Program and Procedures 



The investigation of the vibratory anchor design first involved 

 contractor testing to confirm the overall functionality and integrity 

 of the design for operation in shallow and deep water. Contractor 

 testing included shallow and deep water tests in sand and clay 

 seafloors. Upon receiving hardware deliverable under terms of the 

 contract, NCEL continued the test program in a variety of seafloor and 

 water depth conditions. A summary of all testing conducted to date 

 is presented in Table 2. 



The purpose of the Laboratory testing is to determine the 

 capabilities and limitations of the initial vibratory anchor design and 

 to establish criteria for improvements. The functioning and performance 

 of the anchor system components were examined individually and collectively. 

 Also, operational aspects of handling and lowering the anchor from 

 various work platforms at sea were noted. 



The test program for the full-scale vibratory anchor prototypes 

 has been somewhat dictated by the availability of work platforms and 

 other support activities. As a consequence, the anchor has been tested 

 with a variety of equipment and under a wide range of conditions. 



Though details of procedures differed to adjust to particular test 

 objectives and the support equipment used, the general procedure for 

 tests were similar. For the shallow water tests (less than 100 feet) 

 the work platform, ship or barge, was held firmly in place either at 

 dockside or in a two-point moor at sea. Then the anchor was assembled 

 and readied on deck, lifted over the side by a crane or ship boom and 

 lowered to the seafloor by a winch. Once on the seafloor the anchor 

 was activated by power supplied on the deck or by the battery power 

 pack contained by the support guidance frame. If embedment was 

 successful, uplift loads were applied through a multiple part line and 

 sheave rigging arrangement. A dynamometer was placed in the system 

 to measure the applied loads. An example of such rigging is shown in 

 Figure 22. 



Loads were applied continuously until breakout. In some tests, 

 attempts were made to hold the applied loads steady for a period of 

 time before applying the next higher load increment. However, movement 

 of the work platform due to ocean swells made it impossible to hold 

 loads perfectly steady even though in some tests a length of synthetic 

 rope was used as part of the load line to attenuate the effect of 

 ship heaving on the anchor. 



37 



