Research On Coupled Thermo-hydro-mechanical Dynamic Response Characteristics Of Saturated Porous Deep-sea Sediments

With the deepening of the ”double carbon” policy,China will vigorously develop electric vehicle technology.The strategic metals such as manganese,cobalt,and nickel in electric vehicle batteries are highly dependent on foreign countries(some more than 90%),so a deep-sea mining strategy is being implemented to ensure the safety of strategic metals.However,the complex seabed working environment is a great threat to the operation safety of the deep sea metal mineral resource mining system,and an efficient,safe and environmentally friendly deep sea mining system is urgently needed.The mining machine is an important part of mining system,which has a direct impact on the mining efficiency of the system.In the field experiment,it was found that the soil in the deep sea mining area is easy to soften under a certain vibration frequency and loses its compressive resistance.This indicates that the soil in the mining area is extremely sensitive and has extremely poor dynamic properties.Aiming at the problem of sediment liquefaction caused by the vibration of mining machine,this paper studies the coupled thermo-hydro-mechanical dynamic response characteristics of saturated porous deep-sea sediments under vibration of mining machine.In this way,the subsidence law and influencing factors of the mining machine on the deep-sea sediments are revealed,and the theoretical basis for the optimal design of the mining system in my country is provided.Aiming at the problem of excessive deformation of deep-sea sediments caused by the vibration of the mining machine,this paper studies the dynamic response of the mining machine vibration on the deep-sea sediments.Combined with the reality of deep-sea mining work and considers the heterogeneity of deep-sea sediments,whose elastic modulus and density will change with depth.Based on the Green-Lindsay generalized thermoelasticity theory and Darcy’s law,a thermo-hydromechanica coupled dynamic response model of homogeneous and heterogeneous saturated porous deep-sea sediments is established.The solutions of physical quantities such as vertical displacement,excess pore water pressure,vertical stress,temperature and changing volume fraction field of the sediment under the action of the mining vehicle vibration are obtained by decoupling them by using the normal mode method,and their distribution diagram with depth is obtained.The effects of the vibration frequency and load amplitude of the collector on the physical quantities of deep-sea sediments,the elastic modulus and density of deep-sea sediments,and the vibration of the collector on the physical quantities of homogeneous and heterogeneous deep-sea sediments are analyzed.The results show that the vibration frequency has a very obvious effect on the vertical displacement,excess pore water pressure,vertical stress and volume fraction field;the greater the load amplitude,the greater the change of the physical quantities of the deep-sea sediments;the heterogeneity of deep-sea sediments has a great influence on the physical quantities in deep-sea sediments.The research results can be applied to the research on the sediment liquefaction mechanism and the stability evaluation of the mining machine during the mining of marine mineral resources.