Mechanical Properties and Energy Evolution Law of Coal-Rock Combination Under Unilateral Restriction load and its Damage Constitutive
To explore the unstable fracture,energy evolution and damage mechanical behaviors of coal-rock combination under load,rock-coal-rock combination samples with different thickness-width ratios were prepared and multiple sets of unilateral compression mechanical tests were carried out based on digital image correlation(DIC)technology and a self-made L-shaped test mold.The mechanical properties and macro-fracture characteristics of coal-rock combination were explored.Based on the thin plate buckling theory,a theoretical mechanical model of the coal wall was constructed and the coal wall stability of the coal-rock combination was analyzed.Furthermore,the dynamic evolution law of the energy of the combination and its damage constitutive relationship were studied.The results are concluded as follows.The stress-strain curve of the composite is mainly divided into four stages,namely,initial compaction stage,elastic stage,yield stage and post-peak failure stage.As the thickness of the coal seam increases,the peak strength and elastic modulus of the combination gradually decrease,while the peak strain gradually increases.The rupture of the sample mainly occurs on the free side of the coal seam.When the thickness-width ratio of coal-rock is less than 1,the cracks penetrate the entire coal seam along the loading direction.However,when the thickness-width ratio of coal-rock is greater than 1,the cracks transfer to the interface between the coal seam and the roof,causing small pieces of damage.The critical stress of coal wall instability increases with the increase of coal seam thickness.With the thickness of the coal seam increases,the energy storage limit of the coal-rock combination increases,while the energy release coefficient first decreases and then increases,and the thickness-width ratio of 1 is the inflection point.According to the Weibull statistical distribution density function,the damage constitutive relationship of the coal-rock combination under the situation of unilateral restriction load was constructed.The test results can verify the feasibility of the constitutive relationship.
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维普
