INTRODUCTION 

 Objective 



The purpose of this report is to present foundation design pro- 

 cedures for small unmanned seafloor installations. This category 

 includes instrument or sensor platforms, test structures, in situ test 

 devices, and other totally submerged non-strategic structures having 

 maximum dimensions of less than 15 feet, submerged weights of less 

 than 4,000 pounds, and which are placed on the seafloor as a single 

 unit. These guidelines are for structures placed in water depths 

 greater than 30 feet, and for periods of from several hours to 

 several years. 



The information presented here is for those who must design and 

 emplace such structures and whose background does not include a famili- 

 arity with seafloor foundation design principles. This information is 

 not intended as, nor is it a reasonable substitute for, a complete 

 foundation analysis which is required for structures of higher monetary 

 or strategic value or of larger size or weight. Foundation analysis 

 for such structures is discussed elsewhere (see, for example, References 

 1 through 10) . 



Background 



Seafloor foundations can be separated into a number of categories 

 (Reference 2) which range from small non-strategic structures, which 

 are relatively insensitive to tilting, to large man-rated structures 

 which are quite sensitive to very slight differential movement. There 

 currently is no report available which is intended to provide guidance 

 for the case of the small, non-strategic structures. These installa- 

 tions do not typically merit extensive site surveys or comprehensive 

 foundation analyses. However, this group includes the vast majority 

 of all installations currently being placed on the seafloor. 



Of the hundreds of such foundations which are known to have been 

 placed, a number have not performed in a totally satisfactory manner. 

 One of the primary causes for these problems was a lack of knowledge, 

 at the time, concerning seafloor foundation design considerations and 

 principles. This report is intended to help satisfy the need for 

 guidance in designing foundations for these installations. 



