Study On The Crushing Characteristics Of Porous Seafloor Sulphides Under High Hydrostatic Confining Pressure

In response to the problem that the existing methods cannot take into account the effect of pore seawater inside the minerals in the crushing simulation of polymetallic sulfides under high surrounding pressure environment,this paper introduces a method combining discrete elements and smooth particles,using the pore pressure diffusion equation to simulate the distribution of pressure inside the minerals,and using the smooth particle interpolation theory to calculate the discrete elements and fluid fields in parallel,and then applying the continuous fluid field on the discrete particles in order to more accurately simulate the effect of seawater pressure on the mineral crushing process.(1)The polymetallic sulfide samples were requested from the China Ocean Sample Collection under the NSF project,and triaxial compression and Brazilian splitting tests were conducted to obtain the mechanical parameters of the polymetallic sulfide samples,which were used to calibrate the polymetallic sulfide discrete element(DEM)model and obtain the discrete element fine view parameters of the polymetallic sulfide.These microscopic parameters are then used to establish the pick tooth crushing model of polymetallic sulfide,and the fluid field is computed using a Python self-programmed smooth particle calculation program,which is inserted into the main loop of the discrete element calculation to establish a two-dimensional discrete element-smooth particle(DEM-SP)model.The correctness of the DEM-SP model was verified by analyzing and studying the cutting process,cutting effect,internal pore pressure distribution,crack distribution and the force on the pick teeth through simulated cutting.(2)The DEM-SP model was used to simulate the cutting process of polymetallic sulfide at different hydrostatic confining pressure,different cutting depths and different cutting speeds,and the results showed that with the increase of hydrostatic confining pressure,the model changed from brittle to ductile,the crack expansion was suppressed,the cutting resistance increased,and the chips became finer;with the increase of cutting depth,the crack expansion gradually changed from partial longitudinal expansion to partial transverse expansion,and the total amount of cracks and cutting resistance are proportional to the cutting depth;with the increase of cutting speed,the cutting resistance will increase rapidly but the growth rate will gradually slow down,and the total amount of cracks generated during cutting will first increase a little and then remain stable.(3)Dimensional expansion of DEM-SP model,calibration,cutting model establishment,crushing process simulation in 3D environment,and crushing simulation with DEM model using the same parameters,comparing the crack generation,cutting resistance and cutting effect in the crushing process of the two models,the results show that the simulation results of 3D DEM-SP model are basically consistent with the 2D model in terms of trend,verifying the results show that the simulation results of the 3D DEM-SP model are basically consistent with the 2D model in terms of trend,which verifies the feasibility of the DEM-SP model in 3D.