Numerical simulation on the influence of borehols arrangement and delay time on coal crushing effects

According to the effect of different charging and boreholes arrangements and delay time on coal crushing effect in coal blasting,this paper used ANSYS-LS/DYNA to carry out numerical simulation and analyzed the calculation results.The results show that the explosion stress wave has an supper position effect in the coal , and the coal is mainly broken by tensile.With the increase of ratios of borehole distance and row distance , the crushing of the coal increased first and then decreased.When the ratio of borehole distance and row distance is 1.5, the peak stress in the center of the triangular of boreholes and the degree of coal fragmentation reached the maximum , which are about 175 MPa and 9.6% , respectively.The cracks around the empty hole were annularly distributed.When a/b were 1.0 or 1.5,the cracks were mainly concentrated inside the triangle.When the delay time between boreholes is 0.5 ms,the cracks dispersion is larger than that of 1.0 ms.The number of cracks increases with the increase of delay time between rows.