Abstract
When using the explicit dynamic relaxation approach (DRA) to model the quasi-static rock breakage, fragmentation, and flow problems, especially the top-coal caving question, introducing numerical damping into the solution equation is inevitable for reducing the vibration frequency and impact speed of mesh nodes, which is significantly affect the fidelity of the computation results. Although the DRA has been widely adopted to simulate top-coal caving, the reasonable value and calibration method of numerical damping are still open issues. In this study, the calibration process of reasonable numerical damping for modeling top-coal caving is investigated by comparing with the experimental results, in which several geometry parameters of the drawing funnel are selected as the calibration indexes. The result shows that the most reasonable numerical damping value is 0.07 for the numerical modeling of interval top-coal caving in extra-thick coal seams. Finally, the correlation between the numerical damping and the physical top-coal drawing process is discussed. The numerical damping indirectly reflects the fragmentation in multi scale of coal mass and friction interaction between coal particles during the caving process, which reduces the vibration intensity of the top-coal caving system and dissipates the kinetic energy.
Highlights
The longwall top-coal caving technology (LTCC) is the most popular mining approach in extra-thick coal seams in China, vigorously promoting the coal production of single working faces up to 10 million tons in many northwestern China coal mines [1,2,3]
Numerical damping dramatically influences the accuracy of static simulation results, and its value is generally related to the mechanical properties of material damage, simulation boundary conditions, contact, and other factors
This paper studies the influence of different numerical dampi on the numerical simulation of top-coal caving and puts forward the damping va methToadb,lew2.hNiucmheirsicarlesaimsoulnataiobnlyschdeemtee.rmined
Summary
The longwall top-coal caving technology (LTCC) is the most popular mining approach in extra-thick coal seams in China, vigorously promoting the coal production of single working faces up to 10 million tons in many northwestern China coal mines [1,2,3]. Compared to the in-situ monitoring, the laboratory physical similar experiment has the advantages in modeling the drawing process and obtaining the displacement data of the coal particles, but it only can get the results of the final distribution of the coals and rocks, which usually is hard to trace back to the initial position of the drawn coals and record the stress variations. The dynamic relaxation approach (DRA) is prevalent in modeling the flow of top coal, which models the static or quasi-static mechanical behavior by introducing a significant parameter, the numerical damping, in its balance equation. Numerical damping dramatically influences the accuracy of static simulation results, and its value is generally related to the mechanical properties of material damage, simulation boundary conditions, contact, and other factors
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