Prediction of deep-sea mining vehicle traction performance based on a new thixotropic constitutive model for deep-sea surface clayey sediments

The safe travel of deep-sea mining vehicles (DSMVs) requires accurate track traction predictions. Constructing a constitutive model utilizing thixotropic theory, from the perspective of the structural evolution of the deep-sea sediment, offers clear advantages in dynamic studies over traditional quasi-static constitutive models. This study investigates the non-Newtonian fluid characteristics of deep-sea clayey sediments and develops a thixotropic constitutive model to predict DSMV traction. Considering flocculation and breakdown dynamics, the study employs structural dynamic equations and state equations to describe the variation of shear response in deep-sea sediments with shear time and shear rate. A combination of shear rate ramp cycling and steady-state shear testing protocols is employed to conduct rheometer tests on deep-sea clayey sediments, effectively isolating the effects of shear rate and shear time to determine the trends in shear response under dynamic conditions. Additionally, the study investigates artificial clay, which is created by adding diatomite–kaolinite composite to bentonite to adjust its activity index. Parametric studies of both artificial clay and deep-sea sediments reveal that the liquidity index and activity index have a significant impact on the non-Newtonian fluid behavior of clayey soils. Furthermore, it was validated that the thixotropic constitutive model, incorporating both parameters, demonstrates superior predictive capability for dynamic shear stress. Finally, based on the constitutive model, the track thrust of DSMV under various operating conditions is predicted. The proposed model shows high accuracy in predicting the traction of DSMV under different conditions, providing theoretical support for optimizing the control strategies of DSMV.