Traction Potential Analysis of Self-Propelled Seafloor Trencher Based on Mechanical Measurements in Bentonite Soil

Shear stress-displacement relationship model of soil is very important to predict the tractive performance of tracked vehicle. Most shear stress-displacement models were proposed for terrestrial field. However, they are not suit for soft seafloor with flow surface and high water content. Based on comprehensive analysis of seafloor soil shear deformation and track segment shear tests, a new empirical model of shear stress-displacement relationship for saturated soft-plastic soil (SSP model) was proposed. To validate the SSP model and evaluate potential tractive force of self-propelled seafloor trencher, a test platform, where track segment shear test and drawbar pull test can be performed in seafloor soil substitute (bentonite water mixture), was built. Series of shear tests were carried out. Test results show that the SSP model can describe the mechanical behavior of track segment in seafloor soil substitute with good approximation. Through analyzing the main external forces, including environmental loads from seafloor soil and sea current applied to seafloor tracked trencher during the trenching process in a straight line, drawbar pull analysis model was deduced with the SSP model. A scale test model of seafloor tracked trencher was built, and the verification tests for drawbar pull analysis model were designed and carried out. Results of verification tests indicate that the drawbar pull analysis model was feasible and effective. The drawbar pull tests also indicated that the SSP model is valid from another side.