foundations involving soft or sensitive clays. Primarily because of 

 the assumptions of undrained shear and of disturbance during vane 

 insertion, the vane shear test has not been used to any great extent 

 on pervious silts and sands. The field vane shear, however, appears 

 to be well suited for the analysis of seafloor sediments and has been 

 used in several limited studies (Dill and Moore, 1966; Richards, 1969). 

 It appears to be preferable to the cone penetrometer test because the 

 failure pattern is more accurately known. The greatest limitation of 

 the vane is its inability to test coarse-grained sediments. 



The cone penetrometer test consists of forcing an inverted circular 

 cone into the ground usually at a constant rate of penetration. The 

 cone is generally forced in from the surface, although it is possible 

 to begin a test at the bottom of a bore hole. The force applied to the 

 cone is recorded as a function of depth. 



The cone penetrometer test has been used in Europe since the 1930' s. 

 It has been particularly emphasized in the Netherlands and is often 

 referred to as the Dutch cone test. The results of cone tests have 

 generally been used in empirical relations for the control of highway 

 and railroad embankment construction and the design of pile foundations. 

 In these cases, the shear strength of the soil is not determined; the 

 cone resistance is used directly in the control or design process. 

 Since the penetrometer progresses into the sub-soil by mobilizing the 

 soil's shearing resistance, it should be possible to evaluate the 

 shear strength in terms of the penetration test results. However, in 

 certain instances the test results may be difficult to analyze because 

 of the data scatter and the soil- type dependency. In general, the major 

 advantages of the cone penetrometer test appear to be (1) its economy 

 and (2) its capability of testing soils such as loose sands and sensitive 

 clays which could not be sampled and tested in the laboratory. 



Approach and Scope 



The Deep Ocean Test In-Place and Observation System (DOTIPOS) 

 (Figure 1) is a remotely controlled bottom platform that was developed 

 for controlled placement and observation of instrumented packages at 

 an undisturbed seafloor site to water depths of 6,000 feet. The vane 

 shear and static cone penetrometer tower, a subsystem of DOTIPOS, was 

 developed specifically to obtain the in-situ shear strength of marine 

 sediments to a depth of 10 feet. The in-situ test tower is also 

 operable to water depths of 6,000 feet. 



This report presents the results of vane shear and static cone 

 penetrometer tests obtained with DOTIPOS at a 100-foot seafloor site 

 and a 600-foot seafloor site. The data from both sites are analyzed, 

 and the results are compared with empirical test parameters obtained 

 for similar terrestrial soils. A performance evaluation of DOTIPOS 

 and the vane shear and static cone penetrometer subsystem is also 

 presented. 



