Numerical simulation study of fan-shaped hole initiation mode with non-pillar sublevel caving method

Fan-shaped hole blasting is a key link in the process of non-pillar sublevel caving method, and the lump rate and fine ore rate after blasting are directly related to the continuity of subsequent ore drawing operations. The finite element software LS-DYNA is used to simulate the blasting process of ore falling in various initiation modes in order to study the influence of the initiation modes of fan-shaped holes on the blasting effect. The evolution law of stress field under two initiation modes, orifice initiation and bottom-hole initiation, is obtained. The effective stress time-history curves of the fan-shaped hole at the orifice, the middle and the bottom-hole are calculated. The field tests of fan-shaped hole blasting with two initiation methods are carried out and the blasting effects of the two initiation methods are compared. The results show that the explosive stress waves are superimposed densely at the orifice of the fan-shaped hole, resulting in excessive crushing and fine ore. The explosion stress wave is sparse at the bottom of the fan-shaped hole, which leads to a large block at the bottom of the fan-shaped hole. The effective peak stress at the orifice of fan-shaped hole is greater than that at the middle and that at the bottom of the hole. The field test shows that the blasting effect of bottom-hole initiation is better than that of orifice initiation. The bottom-hole initiation has lower lump rate and fine ore rate. Using bottom-hole initiation and orifice interval charging in fan-shaped hole blasting is helpful to reduce the lump rate and fine ore rate.