Smooth Blasting Technology and Application of Straight Hole Cutting with Three-Arm Rock Drill in Small Section Tunnel
A parallel pilot tunnel with a section size of 6.5 m×6.5 m in a railway tunnel is taken as an example.In view of the practical engineering problems such as the inability of the three-arm rock drill to realize the inclined cut and the long ventilation time after blasting due to the limitation of space in the tunnel,a smooth blasting technology of three-arm rock drill combined with composite straight cut is proposed.Blasting parameters are designed,researched and applied.The results show that the average cycle footage of the blasting scheme can reach 2.8 m to3.0 m,the hole utilization rate is93%to96%,the excavation contour wall is smooth,and there is no obvious 'dislocation' phenomenon between the blasting cycles.Compared with manual drilling,the three-arm rock drill combined with the composite straight-hole cutting smooth blasting operation can reduce 5 manual workers,save ventilation time by 0.4 h per cycle,and save about 1,570 yuan in construction cost,which has significant technical effect and economic value.
railway tunnelthree-arm rock drillstraight hole cuttingblasting parameterhollow pore
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