Investigation of torsional penetrometer for simulation of track-soft clay interaction

Underwater track vehicle will compress and shear the soil as it walks over a soft clay seabed. The compression reflects the depth of penetration and the strength of clay, and the shearing decides the traction that clay could provide. Traditional bevameter technique comprises two separate sets of tests, one is a plate penetration test and the other is a shear test, to simulate this process, ignoring the interaction effect between compression and shearing. In this paper, a new work method of torsional penetrometer is proposed, unifying the compression and shearing of seabed into the sequential penetration and torsion of the penetrometer. The validity and feasibility of the torsional penetrometer concept are verified by comparisons with the previous indoor model tests. In view of the normal solidified soft clay common in the deep sea, by means of finite element method connected with Modified Cam-clay Model, the sensitivity analysis of grouser height and pitch is conducted based on the torsional penetrometer. Finally, the influence of track parameters on the mobilized strength of soft clay seabed is explored. The results show that the grouser height and pitch have a significant effect on the strength of soft clay, and appropriately increasing the tooth height and reducing the pitch will help to give full play to the strength of soft clay.