Investigation On The Traction Of Deep-Sea Polymetallic Nodule Collector

In order to achieve high-quality economic development and promote the improvement of the ecological environment,China has put forward the goal of carbon peaking,carbon neutrality and the strategy of converting old and new energy,resulting in a rapid increase in the demand for some strategic metal resources.The deep sea is rich in such mineral resources,and the development of deep-sea mineral resources has become an inevitable trend to solve the shortage of China’s resource supply,and it is also an important guarantee for achieving China’s dual carbon goals and promoting innovation-driven highquality development.Deep-sea polymetallic nodules are one of the most commercially promising deep-sea solid mineral resources,and crawler collectors are currently a widely recognized method of mining equipment for mining polymetallic nodules.In order to ensure the collection efficiency of deep-sea polymetallic nodules,the study of driving performance and stability of crawler collectors has become an important topic in the direction of deep-sea mining.The traction of the collector when working underwater is provided by the interaction of the tracks with the deep-sea soil.Therefore,in order to evaluate the traction performance of deep-sea crawler collectors,it is important to study the tooth-soil interaction and soil failure mode during driving.Based on the discrete element method,the influence of key parameters of crawler on soil failure mode is studied,and the track parameters and soil failure mode are comprehensively introduced into the soil thrust model.Aiming at the shortcomings in the classical static traction calculation model of existing tracked vehicles,a new dynamic traction calculation model is proposed considering the dynamic change law of crawler-soil interaction during crawler operation.The main research contents and research results of this paper are as follows:(1)Based on the physical and mechanical properties of deep-sea fine soft sediment,the simulated sediment was configured for laboratory tests,and the numerical model of deep-sea sediment was established by using DEM for simulation test verification.By comparing the results of laboratory and numerical tests and checking with the mechanical properties of in-situ sediment,the reliability and rationality of the simulation of deep-sea sediment by discrete element are proved,and the process of tooth-soil interaction is analyzed by using discrete element software.(2)Based on the tooth-soil interaction theory,the crawler shear model is established in the discrete element software,the test results are analyzed and compared with the theory,in order to more accurately describe the shear stress curve under the shear action of different track parameters,a new shear stress-strain model-Magic Formula is introduced.The results show that Magic Formula can describe the shear stress curve better than the traditional shear stress expression,and provide an effective expression tool for subsequent dynamic traction research.(3)Discrete element software was used to analyze particle displacement,contact,force chain and other conditions under track shear,and the influence of track gear height to distance ratio on soil failure mode was studied.The track height to distance ratio,soil failure mode and soil thrust were combined for analysis.According to the analysis,the soil failure behind the teeth can be approximately regarded as the direct shear failure mode when the crawler height and distance ratio is large.With the decrease of the crawler height and distance ratio,the soil failure zone behind the teeth produces a uniformly distributed inclined shear plane,and the soil passive failure occurs at this time.(4)Combining with related parameters of harvest-car for sea test,the dynamic and periodicity of harvest-car motion is analyzed,a new dynamic tractive force calculation model is presented,and the correctness of the calculation model is verified by comparing with the numerical simulation results.Compared with the traditional model,the dynamic tractive force calculation model can describe the changes of tractive force in terms of time and displacement,and show the periodicity and fluctuation of dynamic tractive force,which provides an effective tool for studying the driving performance of deep-sea crawler harvester.