Dynamic mechanical properties and numerical simulation of fractal coal-rock cemented bodies

Zhu Changxing; Huo Jiaxin; Wu Dazhi

doi:10.16186/j.cnki.1673-9787.2024030053

Abstract：Objectives To investigate the influence of particle breakage degree on the dynamic mechanical properties of coal-rock cemented bodies.Methods Based on the theory of solid particle distribution in loose media,loose coal samples with varying degrees of fragmentation were prepared using fractal dimensions of 1.4,1.7,2.0,2.3,and 2.6.These were mixed with cementitious materials in proportion and cured to form standard specimens.Split Hopkinson Pressure Bar(SHPB)tests were conducted to evaluate the dynamic properties,and the SHPB test process was simulated using the finite element software LS-DYNA for com-parative analysis.Results The compressive strength was found to be the lowest at a fractal dimension of 1.7 and the highest at 2.6.The degree of coal fragmentation significantly affected the dynamic mechanical be-havior of the specimens.The internal energy of the cement matrix was considerably greater than the com-bined internal energy of coal particles of different sizes.Numerical simulation results-including peak stress,final strain,and failure modes-were in good agreement with the experimental results.Within the particle size range of 0～20 mm,specimens with a higher mass proportion of 0～5 mm fine particles exhibited greater overall strength.The dynamic compressive strength of the cemented body decreased initially and then increased with increasing fractal dimension.Similarly,the energy dissipation under dynamic compres-sion also showed a decrease-increase trend.A gradation corresponding to a fractal dimension of 1.7 was found to be unfavorable for the mechanical performance of the cemented body.The cement matrix served as the primary energy storage and dissipation medium.Reasonable selection of HJC model parameters allowed the numerical simulation to accurately reflect the dynamic mechanical behavior of the cemented specimens.Conclusions The findings provide technical support for future coal and rock grouting practices.