Research of cumulative energy blasting technology with deep and shallow hole combined in hard roof

To solve the problems of low crack rate and large overhanging roof after directional presplitting cumulative blasting technology is implemented under the condition of hard roof，through theoretical analysis，numerical simulation and field monitoring，the deep and shallow hole combined cumulative energy blasting technology is proposed This paper analyzes the problems of single deep hole combined cumulative energy in hard roof，and points out that optimizing the layout of boreholes and blasting parameters is the main way to improve the blasting effect The technical principle of deep and shallow hole combined cumulative energy blasting is studied，and the theory of combined energy field and mechanical mechanism of combined pilot hole are put forward During the deep and shallow hole blasting，the stress field of the inner section and the outer part can be formed At the same time，the outer part of the deep hole can play the role of the pilot hole in the shallow hole blasting，and finally form the presplitting surface within the scope of the roof cutting Through the monitoring of blasting effect，the crack rate in the hole is increased by 30%，and the variation law of roof pressure is obtained The roof falling and filling in time can eliminate the fracture impact of hard roof and reduce the difficulty of surrounding rock control The research results can provide a reference for directional presplitting high-efficiency cumulative energy blasting under the condition of hard roof