stages will usually Improve the end product immensely. Once the 

 general configuration has been determined, the individual elements 

 can be sized. 



Bearing Capacity 



The bearing capacity of a seafloor soil is dependent upon the 

 type and size of footing used and upon the engineering properties of 

 the soil profile. These properties, normally determined through 

 laboratory analysis of core samples or in situ testing, will often not 

 be evaluated for the exact sites for structures in the category covered 

 by this report. For this reason the available data representing the 

 worst likely situations (Reference 11 includes an excellent collection 

 of this type of data in unanalyzed form) was analyzed to determine a 

 minimum likely soil strength profile. The worst likely situation was 

 taken as the weak and compressible cohesive soils typical of the deep 

 ocean floor and shallower basins and bays. The minimum likely was that 

 strength profile which was exceeded by 90 percent of the data (95 percent 

 or larger would have been desirable; however, there is not sufficient 

 data to make the results of its use significant) . 



The foundation elements are sized on the basis of the total 

 vertical force applied to the soil by the installation (primarily due 

 to the submerged weight) or that portion applied to the individual 

 foundation element (1/3 or 1/2 of the total in the most simplified cases 

 with no lateral forces) . The allowable loads which can be supported 

 by strip footings and spread footings are shown on Figure 3, parts (a) 

 and (b) , respectively. These curves are based in part on bearing 

 capacity equations and relationships from References 12, 13, and 14. 

 The values from Figure 3 contain an adequate factor of safety and 

 may, therefore, be used directly in the foundation design. These 

 values are minimums applicable to all the world oceans except areas 

 of very rapid deposition such as near the mouths of large rivers. 

 Such areas require more detailed analysis (see for example Reference 1) . 

 When the bottom material is known to be a clean sand (such as that 

 found on most beaches) the values of allowable bearing load may be 

 doubled for all footings. 



In sizing the foundation elements on the first trial, it is 

 advisable to use twice the vertical force attributable to the submerged 

 weight alone. This is to account roughly for the effects of overturning 

 due to current drag and other factors. In the subsequent section on 

 "Overturning" this approximation is checked and corrected. If the 

 seafloor is known to be rock, bearing capacity, as such, will not be a 

 problem. However, the overall dimensions of such a foundation or its 

 elements may be sized as if it were for a clean sand bottom. 



