INTRODUCTION 



Subject and Purpose of Report 



This report presents the results of in-situ plate bearing tests performed 

 on cohesive seafloor sediments located at sites ranging in water depth from 

 100 feet to 6,000 feet in the vicinity of the Channel Islands off the coast of 

 Southern California. The work was sponsored by the Naval Facilities Engi- 

 neering Command. The objectives of this report are: ( 1 ) to present an 

 analysis of the results of the two most recently performed series of in-situ 

 plate bearing tests, (2) to present a scheme for correlating the results of in-situ 

 plate bearing tests with those of laboratory tests on core samples, (3) to report 

 on a general procedure for predicting short-term foundation settlement from 

 data on cores, and (4) to present updated information on NCEL's plate bear- 

 ing test equipment and data processing procedures. 



Analysis of Problem 



The exploration and utilization of the ocean is progressing at an ever 

 increasing rate. Frequently this endeavor involves the use of the seafloor to 

 support foundations for such diverse structures as equipment test stands, 

 acoustic arrays, and bottom-sitting submersibles. Some items are emplaced 

 at one location for long periods of time while others are moved from site to 

 site in the course of their use. Some structures are very large and apply 

 significant stresses to great depths in the sediment while others are small, 

 lightweight, and are supported primarily by the upper several feet of sediment. 

 At present the weight of many underwater structures is reduced or these struc- 

 tures are even made positively buoyant by the use of buoyant elements. In 

 these cases the foundation may be provided primarily to resist loads due to 

 overturning moments on the structure or simply to keep the structure at one 

 location on the seafloor. In most of the above-mentioned situations the pos- 

 sibility of a bearing capacity failure and the resulting excessive settlement or 

 tilting of the structure needs to be investigated; failure to do so may render 

 a structure useless for accomplishing its designated mission. 



