INTRODUCTION 



This report describes the development of a seafloor soil test 

 device capable of performing cone penetration tests to 40-foot sediment 

 depths. The general objective of the project was to provide the Navy 

 with a means of gathering geotechnical data on cohesionless soils to 

 soil depths suitable for shallow piles and propel lant anchors. The 

 equipment developed was to be operable in water to 200 feet deep and 

 suitable for operation from small anchored barges and other support 

 vessels typical in Navy construction. The data provided from the elec- 

 trical friction cone on the device was to be suitable for measuring soil 

 strength and for soil classification. 



Approximately 60 penetration tests were performed in various areas: 

 in Norton Sound, Alaska; off Port Hueneme, Calif.; in San Francisco 

 Bay, Calif.; and off Coronado, Calif. The data from some of these are 

 presented in this report and data of this type can be directly applied 

 to pile design using established methods. They are also suitable for 

 selecting appropriate anchors and evaluating anchor performance. This 

 development was funded by the Naval Facilities Engineering Command. 



BACKGROUND 



The Navy is responsible for constructing a variety of facilities in 

 the nearshore and continental shelf regions (i.e., in water depths to 

 1,000 feet). These include small to moderate-sized pile-supported 

 platforms and pile-supported piers and elevated causeways, as well as 

 various types of moorings incorporating pile, direct-embedded, or con- 

 ventional drag-embedded anchors. Knowledge of geotechnical properties 

 of cohesionless materials, correctable to end-bearing-capacity factors, 

 skin-friction-capacity factors, horizontal subgrade reaction moduli, and 

 other data is required for the design of these facilities. For the 

 majority of Navy situations, it is adequate to limit the soil depth of 

 geotechnical property determination to 40 feet. This choice of depth 

 was based on the depth of shallow piles used in Navy operations such as 

 for the elevated causeway system (ELCAS) and the depth of embedment of 

 propell ant-embedment anchors. 



At the initiation of this work, systems capable of measuring the 

 required parameters and of reaching subbottom penetrations to 40 feet in 

 sands required use of either (1) a borehole, (2) diver-operated or 

 remotely operated heavy equipment, or (3) coring and property estima- 

 tion. These systems are undesirable for Navy use for several reasons. 

 For instance, the major disadvantages of making a borehole are that the 

 process is time-consuming and expensive and requires special drill ships 

 or at- sea platforms to complete the work. 



