Experimental design for rock breaking of viscoelastic surfactant slurry abrasive jet
[Objective]Abrasive water jet(AWJ)technology,which effectively breaks rocks in thin coal seams,faces challenges like nozzle blockage and low cutting efficiency owing to particulate agglomeration and deposition.Recent advancements have shown that adding a viscoelastic surfactant(VES)to an abrasive slurry provides benefits such as low friction,high viscosity,and stable suspension.Inspired by the progress made in the abrasive slurry jet(ASJ),this study designed a comprehensive teaching experiment to investigate the rock-breaking performance of ASJs with VES additives.[Methods]A comprehensive experimental study on rock breaking using VES ASJ was conducted on a high-pressure jet cutting platform.Prior to the experiment,VES was prepared using octadecyl trimethyl ammonium chloride,sodium salicylate(NaSal),and C3H8O in a 1:5:1 mass ratio.SiO2 particles were added to the VES solution at a concentration of 15 kg/m3 to form an abrasive slurry.Stability was assessed through static visual observations,revealing a stable suspension of SiO2 owing to the VES's three-dimensional entangled network structure of the VES under the action of counter ions.Based on similar material modeling methods,the artificial rock samples used for rock-breaking experiments were made of architectural gypsum,cement,and quartz sand in a 1:4:5 mass ratio.The relationship between the uniaxial compressive stress and loading displacement in both man-made rock samples and natural marble samples exhibited similar trends,indicating that they had comparable mechanical properties.[Results]This study examined the particle-carrying capacity,flow pattern,and rock-breaking ability of ASJs,along with the morphology and size of the resulting rock crushing pits.Experimental results clearly show that the particle-carrying rate of ASJ increases rapidly with jet velocity and is higher with VES additives than with AWJ.This improvement is attributed to the VES's entangled network structure,formed under the action of counter ions.Owing to the low friction and high viscosity of VES,high-speed camera recordings of ASJ reveal well-concentrated fluidic beams with flow structures that remain smooth and stable under different jet pressures.VES enhances jet stability and cohesion,minimizing disturbances from air entrainment.Jet pressure directly impacts rock-breaking performance.As jet pressure increases,so do the depths and widths of erosion pits.However,rock-breaking efficiency initially increased with increasing pressure and then declined following a parabolic function.[Conclusions]To meet the educational needs of the"Intelligent Tunneling"course,a hierarchical experiment was designed,containing abrasive slurry preparation,physical property testing,and rock-breaking investigations.The experiment involves many areas,such as green mining of coal resources,intelligent mining,and energy saving,which can nurture top-notch talent in the mining industry.
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