Abstract: In order to solve the problem that it's difficul to adopt traditional smooth blasting（requir⁃ ing the full-hole installation of bamboo strips and detonating cords，which is costly and involves complicat⁃ ed procedures）in small and medium-sized underground mines，due to their narrow tunnel sections and complex geological conditions，based on the engineering background of the Huaaobaote Ag-Pb Mine in In ⁃ ner Mongolia，low-cost and efficient smooth blasting technology without bamboo strips and detonating cords is proposed.Through theoretical analysis and numerous industrial tests，the explosive loading struc⁃ ture of the smooth blasting holes is optimized，the thickness of the smooth blasting layer（625 mm），the hole spacing（500 mm），and the line explosive density（150 g/m）are reasonably designed，and the maxi⁃ mum stable detonation distance of ϕ32 mm emulsion explosives in 4.0 m deep holes（1 050 mm）are fully utilized.A three-stage air interval filling structure combined with hole mouth blocking is adopted.The en⁃ gineering application results show that this method successfully eliminates bamboo strips and detonating cords，reducing the single-cycle operation time by 1.8 h，lowering labor intensity by 37%，and reducing the direct blasting cost by 50%（saving 235 RMB/m）;the semi-hole formation rate of the tunnel increases to over 92%，the contour over-cutings and under-cuttings are controlled within ±10 cm，the damage depth of the surrounding rock is reduced by 35%，the support engineering volume is reduced by 22%，and the formation quality reaches the leading level in the industry.This technology simplifies the process，is low in cost，and has stable effects，providing a replicable and easily-promoted green and efficient smooth blasting solution for small and medium-sized mines.

Key words: underground mine, smooth blasting, tunnel excavation, detonation gap distance, charge structure