Regional Characteristics of Deformation and Failure of Coal and Rock under Local Loading

Abstract

Abstract The deformation regional characteristics and fractal characteristics of crack propagation in raw coal and briquette coal under local loading were studied. The results show that the stress-strain curves of the two samples under local loading have typical stage characteristics, the deformation of the raw coal samples in the compaction stage is greater than that of the briquette coal samples, and the peak strength of the two samples increases linearly with the increase of the loading area. With the increase of loading time, the strain of the nonloading zone shows a slow growth stage and a strain stable stage. The farther away from the loading area, the smaller the strain and the strain rate are. Under local loading, the relation of the fractal dimension of the raw coal surface and strain can be described as a cubic function, while the relation can be expressed by a quadratic function for the briquette sample, and the relation of the fractal dimension and loading area of the raw coal and briquette both can be described as a quadratic function. Under uniaxial compression, the briquette coal mainly undergoes tensile failure, and the raw coal mainly undergoes x-type shear failure. Under local loading, the raw coal and briquette coal microcracks started propagation from the easy fracture zone, and the main control crack is located in the interface between the loading zone and the nonloading zone.