Numerical Study on the Tensile Strength and Failure Characteristics of Coal Mass with Pressure Relief Drilling

Pressure relief drilling is an effective measure for rockburst prevention and control. However, the tensile behaviors of the coal and rock mass with boreholes are prominently changed. Therefore, the significance of tensile loading condition on the mechanical properties of coal mass with boreholes should be highly valued. In this paper, the discrete element numerical method is used to perform Brazilian splitting simulations on coal discs with holes. The effects of hole geometry parameters (diameter, number, layout inclination angle, and spacing) on the tensile properties and failure characteristics of hole-containing coal discs are investigated. The findings indicate that the tensile strength of the hole-containing disc first increases and then decreases with increasing hole diameter, number, and spacing, while an opposite trend is observed with increasing layout inclination. Besides, tensile stress concentration tends to occur around the holes and the grain displacement typically exhibits tensile cracking mode. Moreover, the tensile strength of the hole-containing disc is most sensitive to the hole number, followed by the hole diameter and spacing, whereas the hole layout inclination owns a limited effect. Furthermore, hole number and diameter exhibit the strong negative correlation with the tensile strength, while layout inclination and spacing of holes have a moderate negative correlation with tensile strength.