no sensitivity values are available for that site. An average sensitivity 

 value of 2.5 to 3.0 was obtained for Site 2, however, erratic values of 

 1.3 and 8.0 were also encountered. There is no noticeable trend for 

 sensitivity with depth. From the lines of best fit in Figures 19 and 20, 

 the sensitivity was expected to increase with depth, however, the 

 experimental error in the undisturbed and remolded vane shear strength 

 values tends to mask any noticeable trend in sensitivity with depth. 



The sensitivities obtained in situ (Figure 26) compare favorably 

 with the sensitivities obtained in the laboratory vane tests (Figures 

 14 and 15) on cores. Sediment sensitivities of 2.5 to 3.0 were obtained 

 for both series of tests performed on the clayey-silt (below 15 inches) . 

 In the 15- inch sandy layer at the top of the soil profile, lower 

 sensitivities were obtained in the laboratory than in the field. This 

 may be attributed to the different circumferential (not rotational) shear 

 rates used in the laboratory and field for the two different soils. It 

 was initially believed that different sensitivities might be obtained 

 in the laboratory and field because of the different remolding techniques. 

 Terzaghi and Peck (1967) state that "the degree of disturbance caused 

 by rotating a vane differs from that caused by kneading a sample in the 

 laboratory". The numerical values of sensitivity determined by the two 

 procedures may, therefore, differ, but the magnitude of difference is 

 unknown. The experimental error for the tests performed in situ and 

 in the laboratory were not sufficient to note any significant trends. 



SUMMARY AND CONCLUSIONS 



1. DOTIPOS , with the vane shear and cone penetrometer tower, operates 

 satisfactorily to water depths of 600 feet. 



2. Several sets of vane shear tests and several cone penetration tests 

 can be performed in an eight-hour work day. 



3. Load handling of DOTIPOS from a Navy ARS or a Navy LST posed no 

 problem when the wave height was less than 5 feet. 



4. Vane shear and cone penetrometer test results, when compared to 

 previous theoretical and experimental results, appear reasonable. 



5. Reasonable agreement exists between laboratory and in-situ vane 

 shear data for Sites 1 and 2; however, the In-situ strengths slightly 

 exceed the laboratory strengths. The disagreement most likely stems 

 from errors in the laboratory test results generated by soil disturbance 

 which originates from poor sampling techniques. 



6. A relationship between sediment clay content and the ratio of cone 

 resistance to vane shear strength appears feasible for seafloor sediments. 

 If this relationship can be established, the cone penetrometer will become 

 a more useful and economical tool in support of a seafloor investigation. 



17 



