There were two main development goals: (1) to obtain data to a soil 

 depth at least as large as the depth required to achieve the rated holding 

 capacity of the Civil Engineering Laboratory (CEL) 20K anchor (30 feet 

 in clay, 15 feet in sand), and (2) to keep the cost low enough that the 

 tool could be considered expendable, thus maximizing operational flexibility. 



Background 



The Civil Engineering Laboratory conducted a study and made tentative 

 recommendations for conducting deep ocean site surveys for anchor installa- 

 tions, Rocker, et al. , 1972. A tentative plan called for soil coring and 

 acoustic subbottom profiling to be the mainstays in providing the information 

 required to site and design anchors. They saw soil strength, penetrability, 

 and thickness, and the occurrence of anamolous conditions (e.g., ice-rafted 

 detritus and small submarine lava flows) as important parameters to 

 determine. One of the conclusions in this report was that the development 

 of simplified in-situ testing equipment would significantly improve the 

 chances of conducting successful site investigations. Rocker recommended 

 that an expendable penetrometer be developed to provide an improved site- 

 investigation capability. 



An additional study of the most suitable technique and equipment to 

 provide the required seafloor data was made by Rocker and Raecke (1972). 

 After studying a wide range of existing and conceptual survey tools, they 

 concluded that a gravity, penetrating, test anchor* was the best tool for 

 acquiring data to design direct-embedment anchors. They also recognized 

 that a dynamic penetrometer was the only truly expedient tool, the easiest 

 and the least costly to use, and, therefore, the most attractive tool 

 if satisfactory data could be acquired from it. Therefore, they recommended 

 that a gravity, penetrating, test anchor be developed and that investigation 

 into the possible development of a dynamic penetrometer continue. 



Work was initiated to develop a penetrating test anchor. A hydrodynamic 

 model study was conducted to determine drag coefficients and the stability 

 of several concepts. Penetration studies with the same models were also 

 conducted. It was determined that to achieve required performance a gravity, 

 penetrating, test anchor would weigh about 3,000 pounds and be about 20 

 feet long. Several disadvantages in the development of such an anchor were 

 noted: (1) it would be difficult to use a device of this size; (2) use would 

 be limited to weather conditions favorable for coring; (3) the time required 

 to perform a test would be as lengthy as that necessary for coring, and 

 therefore the number of tests would be limited; and (4) the extended onsite 

 time would jeopardize the security of a site. Therefore, it was decided that 

 a re-evaluation of its usefulness was in order. The result of the re- 

 evaluation was a recommendation to stop development of a gravity, penetra- 

 ting, test anchor and to begin development of an expendable penetrometer. 

 It was thought that an expendable penetrometer could expediently meet any 

 operational requirement, provide knowledge about lateral soil variability 

 when compared to sediment core data, provide knowledge about anomalous 

 conditions (dependent upon the number of tests) , and give an indication of 

 soil penetrability and strength. 



* In concept only, the gravity penetrating test anchor was never developed. 



