Mechanism and Application of Deep and Shallow Hole Collaborative Blasting in Nearly Vertical Coal Seam

In view of the problems of high boulder yield (32%), difficult coal gangue sorting and others caused by the adoption of single deep hole blasting scheme for the nearly vertical coal seam (inclination angle 75°-85°) in the 1164^# mining area of Haishiwan Coal Mine of Yaojie Coal and Electricity Group in Gansu Province, based on the stress wave superposition theory and the energy cascade release principle, a deep and shallow hole collaborative blasting technology is proposed. By establishing stress wave transmission equations and cumulative damage models, combined with analysis of unit volume energy density and prediction of fissure expansion speed, the optimal parameter combination for deep holes (Φ80 mm×3.0 m) and shallow holes (Φ40 mm×1.2 m) is determined; A portable type of drilling parameter acquisition system is developed to achieve digital management of drilling and blasting process. The 6-month on-site application results show that the qualified lumpiness of coal bodies after blasting is accounted for 92.3%, with an improvement of 24.3 percentage points compared to the original scheme; The vibration speed is reduced to 2.0 cm/s, which completely meets the national standard; The consumption quantity of unit dynamite is reduced to 0.38 kg/t. This technology provides a fully new technical approach for efficient mining of nearly vertical coal seams.