Development and teaching practice of top-coal migration trajectory monitoring experimental platform
[Objective]Fully mechanized top-coal caving(FMTC)technology is the primary method for mining thick coal seams.A crucial research area in FMTC is understanding the migration pattern of top coal,with migration trajectory being foundational.Traditional methods for monitoring top-coal migration trajectories and placing measurement points have certain drawbacks.The equivalence of particle migration trajectories obtained through experiments to actual trajectories within the model remains debatable.[Methods]This paper analyzed different experimental materials and tracking methods,ultimately selecting acrylic considering its similar density to coal and high plasticity,serving as the"coal block"for the experimental platform.Acrylic's high strength makes it suitable for the structural framework of the experimental platform,which must withstand horizontal pressure generated by the coal while minimizing interference with the coal tracking process.Electromagnetic tracking technology was chosen because it can position and track objects even with obstructions.An experimental platform for monitoring the migration trajectory of top coal in the FMTC has been developed,comprising a model frame,FMTC support,auxiliary hinge wheel,magnetic field emitting device,trajectory recognition device,and data acquisition system.This platform can project electromagnetic waves,allowing precise positioning and accurate identification of top coal influenced by geological conditions and mining techniques.Physical simulation experiments of top coal particle migration at different positions were conducted using this platform.A multistage experimental mode was designed,including"model construction,marker point installation,simulated coal caving,data collection,and trajectory inversion,"which deduced the top-coal caving body.[Results]By analyzing the monitoring coordinate sequences collected by the system,the following observations were noted:① top coal particles generally move linearly from their original position to the coal caving opening.The farther the particle from the opening,the longer the migration trajectory,conforming to the basic assumptions of the B-R model.Trajectories on the support side are denser and more concentrated than on the goaf side.② The migration trajectory is divided into two zones based on the influence of the protective and tail beams of the FMTC support.In the unconstrained zone(tail beam),trajectories align with the B-R model,intersecting at the midpoint of the coal caving opening.In the constrained zone,trajectories intersect at the hinge point of the protective and tail beams.[Conclusions]The development of this experimental platform for monitoring the migration trajectory of top coal substantially enriches the teaching of the"Mining Science"course.Students can visually observe the technical principles of FMTC and the movement process through experiments.This aids in deducing the equation of the top-coal caving body in FMTC,deepening students'understanding of FMTC technology and migration patterns,and greatly enhancing teaching effectiveness.
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