The objective of this effort was, therefore, to collect and summarize 

 all available information on the performance of seaf loor foundations. This 

 information, along with appropriate analysis, could be expected to contrib- 

 ute significantly to improving the capability for designing safe, reliable, and 

 economical seafloor foundations. 



It was not possible to satisfy totally this objective because of a 

 general lack of available detailed knowledge concerning design and perfor- 

 mance of existing seafloor foundations. However, based on the available 

 general information, it is possible to make the following generalizations 

 concerning foundation design parameters: 



1 . On cohesive soils, excessive total or differential settlements have 

 been the causes of inadequate performance much more often than have bear- 

 ing capacity failures. 



2. Bearing pressures as low as 1 80 psf have caused bearing capacity 

 failures in cohesive soils. Known installations supplying pressures in the 40- 

 to 100-psf range have experienced no such failures although, in some cases, 

 they have been subject to large settlements and other performance problems 

 such as undermining resulting from scour or biological activity, downslope 

 skidding, and improper installation. 



3. On granular soils, where static bearing capacities are much larger, 

 other factors have been the source of most performance problems — these 

 factors have included scour due to bottom currents or surge, errors or unfore- 

 seen difficulties during installation and construction, excessive current or surge 

 forces, inadequate knowledge of topography, and biological activity. 



The general analysis of the experience to date with seafloor 

 foundations has pointed out foundation systems which have been success- 

 ful and those which have not been. This analysis has also drawn attention to 

 conditions unique to the seafloor environment which must be considered in the 

 design of foundations. As a result of this analysis, the following three general 

 conclusions have been reached: 



1 . In many cases there has been insufficient, or total lack of, reference 

 to foundation design principles. 



2. Although most foundation performance problems have not resulted 

 in catastrophic failures of the installation, they have often necessitated very 

 expensive remedial actions. 



3. The number and sophistication of seafloor installations are 

 increasing; therefore, the importance of improving the reliability of foun- 

 dation performance is becoming more critical. 



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