On Smooth Blasting Technology Assisted with Short Heading Cut Blasting for Tunnels with Small Sections and Long Steep Slopes

In industrial and mining engineering construction, due to the non-standard cross-section form and small cross-section size of mining tunnels, the working space is restricted and so results in a low degree of mechanized construction. Also, the existence of a long steep slope makes the tunnel easy to encounter blasting hole collapse and roof caving in the "drill and blasting" construction process, which could increase the construction cost and delay the construction period. To this end, based on the "drill and blasting" construction method principle, it proposes to adopt the cut blasting technology for the short heading on the tunnel face in combination with the design optimization of face blasting parameters and hole patterns. Furthermore, by means of the characteristic initiation system network composed of electric initiation, non-electric initiation and millisecond delay initiation, the full-section smooth blasting effect in one blasting process is realized for mining tunnels with a small section and long steep slope. The implementation of this method in the mining tunnel engineering of the Haitong cement project of Tibet Development and Investment Group Co., Ltd. could not only solve the problems of hole collapsing at the top of the tunnel and over-break due to excessive blasting angles, but also shorten the construction period by 120 days and save nearly RMB 8,962,000 in construction cost.