Experimental Study On Microscopic Liquefaction Mechanism Of Shipborne Solid Bulk Cargo

Since the "Mega Taurus",a bulk carrier carrying nickel ore from the Philippines to Japan,capsized in 1988,25 bulk carriers carrying nickel and iron ore have sunk with heavy loss of life.The maritime transportation safety of solid bulk cargo has attracted great attention from the shipping industry.IMO,DNVGL,Class NK and other international organizations have successively issued the maritime transportation safety standards of solid bulk cargo to reduce the risk of liquefaction of solid bulk cargo."Solid Bulk Liquefaction: Strategies for Effective Control",a three-year interdisciplinary project funded by Lloyd’s Register of Shipping,was launched in 2020 to improve the identification of solid bulk liquefaction risks.At present,the problem of liquefaction of solid bulk cargo has not been effectively solved,which greatly affects the safety of maritime transportation of solid bulk cargo and seriously restricts China’s mineral resources reserve and import efficiency.From the phenomenon of "wet bottom",dense mud and free liquid surface in the liquefaction process of solid bulk cargo,it can be seen that moisture migration is an important cause of liquefaction.Liquid bridge is the basic form of water in solid bulk cargo.Its dynamic evolution directly affects the liquefaction evolution process.In this paper,the tensile,fracture,water retention and moisture migration characteristics of liquid bridge between spherical particles were studied experimentally.Firstly,the liquid bridge between particles measurement experiment platform was built based on the principle of cantilever beam,and the dynamic liquid bridge force between particles was measured.Secondly,the relationship between dynamic liquid bridge force and particle size,liquid bridge volume,liquid bridge stretching speed and particle size ratio was investigated to determine the critical fracture distance of liquid bridge.Thirdly,the limiting liquid holding capacity under different particle size,particle number and particle spacing was investigated,and the critical conditions for static particles to transfer water were analyzed.Finally,the water migration behavior of particles with relative motion was analyzed,and the mesoscopic reason of solid bulk cargo liquefaction was given.In this paper,the complex evolution behavior of liquid bridge in the process of relative movement between solid bulk cargo particles was simulated.The advancing mechanism of liquid bridge evolution to water migration was analyzed,and the mesoscopic mechanism of solid bulk cargo liquefaction was further explored.It can provide scientific and effective theoretical guidance and technical support for the safe transportation of solid bulk cargo at sea.