Restrictions on seismic impact of blast in the open-pit border zone at the open-pit and combined mining

The combined mining under the condition of underground mining in the aquifer rock mass of the open-pit sides raises an acute issue of joint drill-and-blast works (D&B). The construction of an underground mine begins normally with the approach of the open-pit mine depth to the final marks. In this situation, if there is a volume for the cutback, it is very small, and the blast works come close to the limit open-pit contour, behind which the protected rock mass is located and in the future the underground mining is supposed to be carried out. The main task in the drill-and-blast works under such conditions is to preserve the stability of this rock mass. The well-timed shielding of the blast and creating the fracture surfaces by the trim blasting reduce the negative impact of the blast on the open-pit side, but do not always prevent the propagation of stress waves caused by the seismic effect along the rock mass. Therefore, restriction of the seismic effect of blast in the border zone is as important for the stability of the rock mass as professional deviated contour holes.