In order to study the dynamic mechanical properties and damage failure law of coal specimens with borehole under impact load,the split Hopkinson pressure bar test system and LS-DYNA finite element numerical simulation were used to car-ry out the dynamic mechanical test and simulation analysis on the raw coal specimens with boreholes with different diameters,and their stress and strain response,crack expansion characteristics,and damage evolution law were studied. The results show that the dynamic compressive strength of coal specimens is weakened by borehole under dynamic loading,and the peak stress and peak strain present the decreasing trend with the increase of borehole diameter. The damage of coal specimens by borehole is oriented,and the cracks are firstly produced in the tensile stress area on both sides of borehole axial direction,and the num-bers of secondary cracks and broken blocks increases with the increase of borehole diameter,which improves the uniformity degree of energy absorption. Based on the HJC constitutive model,the mechanical parameters are calibrated,and the numerical simulation is in good agreement with the experimental results. The simulation range of borehole diameter is further expanded,and the relationship between the peak stress,strain and borehole diameter variation of coal specimens with borehole is ob-tained by fitting. The distribution of equivalent stress and the evolution process of damage and fracture in coal specimens with borehole are visually displayed,and the existence of borehole will cause significant stress concentration and accelerate the damage of coal specimens. The research results can provide certain scientific reference for the design of large-diameter pres-sure relief boreholes in coal seams under dynamic load impact conditions.
impact loadsplit Hopkinson pressure barcoal specimens with boreholemechanical propertydamage destruction
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