Background 



During the spring and summer of 1969, the author of this report 

 accompanied scientists from NUC (Naval Undersea Research and Development 

 Center), San Diego, on an extended oceanographic investigation of 

 18 areas in the southwest Pacific and eastern Indian Oceans. 

 Each area belonged to one of the following three physiographic provinces: 

 (1) continental terrace (shelf and slope) , (2) abyssal plain, and 

 (3) abyssal hill. These provinces formed sedimentary environments in 

 which distinctive sediment types were apt to be found. The NUC scientists 

 studied the environment of each area with respect to water chemistry, 

 biologic activity, and sediment type. Studies were accomplished by 

 employing such oceanographic tools as Nansen bottles, trawl nets, and 

 gravity corers. Data obtained from bathythermographs, echograms, and 

 subbottom profilers also helped establish the characteristics of 

 the particular province. 



While aboard ship, the author, assisted several marine geologists 

 in obtaining and classifying sediment samples from the site. The 

 samples, which included red clays, oozes, and terrigenous silts and 

 clays, typified the materials found in major troughs, basins, and plains 

 of that geographic region. Within several hours of sampling the sediment, 

 the author performed tests that measured the original and remolded 

 vane shear strengths of sediment sections from various depth increments. 

 The tests utilized a motorized vane shear apparatus to establish the 

 undrained stress response during controlled conditions of strain. 



Difficulties associated with performing other laboratory tests 

 aboard ship prevented the immediate completion of the soil classification 

 program; consequently, each sample was visually identified, labeled, 

 and stored at 4 degrees Celsius (Centigrade) until the ship returned to 

 the United States. Once the samples were received at NCEL (Naval Civil 

 Engineering Laboratory) (about 6 months after obtaining the samples) , a 

 series of laboratory tests was performed on the cores to complete the 

 engineering classification. These tests included the determination of 

 the sample's water content, Atterberg limits, specific gravity, grain 

 size distribution, and carbonate carbon and organic carbon contents. 



Approach and Scope 



This report summarizes the results of the shipboard vane shear 

 test program and the subsequent series of laboratory identification 

 tests. These results are presented after a brief summarization of 

 the techniques involved in sampling the material, in performing the 

 vane shear tests, and in identifying the samples. The initial portion 

 of the report also considers the theory of vane shear tests and the 

 cause of strength variations within the soil strength profile. 



