Application and carbon dioxide two-step barrel cut blasting technology in coal mine shaft

According to the limiting factors of vertical shaft blasting construction and explosive controlled conditions, combined with the characteristics of the existing cutting technology, this paper puts forward the carbon dioxide two-step cylindrical cut blasting technology. First of all , this paper introduce the principle of carbon dioxide blasting technology and the structure of carbon dioxide blasting device ,expounds the core idea of two-step cylindrical cut.“two-step” refers to a description of the cut form from two dimensions of “time and space”. The rock in the cut area is divided into two steps with different depths, and the blasting sequence of the cut hole is divided into two different stages. At the same time, the cut hole is arranged into two rings with different diameters of the double cylinder shape, the center of the cut ring is arranged with a empty hole, the first-order cut hole in the inner ring, while the second-order cut hole in the outer ring, two cut holes are inclined to the center hole at a certain Angle, so that the top area of the cylinder is large and the bottom area is small. The first-order cut hole is blasting first, and the second-order cut hole is blasting later. This two-step cylindrical cut fully combines the advantages of “two-step” and “cylindrical cutting”, that the center hole provides weak free surface and compensation space for the blasting hole, while the first-order and the second-order cut hole are surrounded by a double cylinder.In this case the blasting is carried out in two stages, which effectively combines the shallow blasting and deep blasting, reduces the clamping force of the rock during the second blasting, expands the area of cutting cavity, and improves the blasting effect. Secondly, by analyse the principle of two-step cylindrical cut blasting technology, and deduce the shear resistance formula of cut blasting and the dynamic formula of blasting cavity, and determine the basic conditions for rock ejection from the cavity under the static action of carbon dioxide explosion gas.At last, by comparing the field application effects of dynamite straight cut blasting and carbon dioxide two-step cut blasting, indicate that the two methods have small difference in the three post-detonation indicators of circulating drill footage, hole utilization rate and cut cavity volume, which further proves that the carbon dioxide two-step cylindrical cut blasting technology is suitable for vertical shaft drilling. It provides a new technical way for vertical shaft cut blasting.