Three-dimensional stress path in deep-sea sediment under the driving load of a nodule collector

Abstract

The quasi-static method was used to study the internal stress path in deep-sea sediment under the driving load of a crawler-type nodule collector. First, the instantaneous stress state of a soil element was calculated according to the theory of elasticity and was compared with the results of a numerical simulation. Next, the relative positions of the load imposed by the nodule collector and the soil element were changed to simulate the driving of the nodule collector to obtain the full-time stress path in the soil. Finally, the stress path and rotation of the principal stress axes in the soil at typical positions were analysed. The results showed that the spatial position of the soil had a significant influence on the stress path. In addition, the stress, peak value of the time-history curve for the principal stress and rotation mode of the principal stress axes showed correlations with the spatial position. Therefore, the stress-loading scheme should be selected according to the actual conditions of a given position in a laboratory test. A method was developed for representing the three-dimensional (3D) rotation of the principal stress axes based on a spherical projection of the direction vector. The proposed method can intuitively show the rotation law of the principal stress axes at any position in the soil during the driving of the crawler.