Experimental and numerical simulation study on mechanical properties of coal-transition layer-rock composite structures
Within deep coal-bearing strata,a prolonged diagenesis process leads to the existence of a lithological transition zone between some coal and rock layers.This transition zone,together with the adjacent rock and coal layers,constitutes a composite structure.To study the influence of the transition layer's height on the deterioration characteristics of the coal-rock composite,a proportionate design of coal,rock,and transition layer artificial materials,as well as a production plan for coal-transition layer-rock(CFR)composite specimens,were initially proposed.On this basis,uniaxial compression tests of artificial CFR composite specimens with varying transition layer heights were conducted.In addition,based on the discrete element numerical simulation software PFC,rigid clusters and spherical particles were used to represent coal and rock particles in the transition layer.Through their proportion changes,a PFC characterization model for the transition layer and CFR composite structure was constructed.Combined with the test results,the model parameters were calibrated,and the algorithm's effectiveness was validated.Both experimental and numerical simulation results indicate that as the height of the transition layer increases,specimen strength,pre-peak dissipated energy,and acoustic emission b initially decrease then increase,while the elastic strain energy shows a progressively increasing trend.The distribution range of numerical simulation micro-fracture angles also initially narrows then expands with increasing height,and the micro-crack initiation area gradually shifts from the coal layer to the transition layer,with the acoustic emission location progressively concentrating on the interface between the coal and transition layer.These results demonstrate that the presence of the transition layer significantly alters the physical and mechanical properties of the coal-rock composite structure.
rock mechanicscoal-transition layer-rock combinationstrength characteristicsnumerical simulationfailure mechanism
万方数据
