| In the mountain tunnel excavation,drilling and blasting method as one of the main excavation methods has low cost of excavation,strong adaptability,higher driving efficiency.For the time being,many research focuses on the influence of disciplinarian and control standards of tunnel blasting,which has been less involved in improvement of blasting technology and technological innovation.In this paper,based on the slit gathering energy effect of the slotted pipe,the annular and longitudinal slotted tubes are designed to form annular and longitudinal slit charges.Firstly,lead-tube blasting test had been done to explore and verifiy its specific effects with the annular and longitudinal slit charges.And then,in view of the cutting blasting drilling efficiency and peripheral holes controling the contours,respectively,blasting test was carried out in the full-face excavation section of the Sangzhi tunnel.The main conclusions are as follows:(1)Experimental phenomena showed slit gathering energy effects in Charge area and non-charge region of slotted pipe,but the gathering energy effects of Charge area are greater than that of the non-charge region;And the main reason is the impact differences between impact jet flow and detonation waves formed at the two sections in the slit.(2)The cut blasting footage and effect is improved and ensured,when cutting hole charge with the annular slit charges,becuase explosive energy utilization efficiency is increased at the bottom circumferential direction of the hole,and the tests show that the effect of annular slit charges is the best when the circumferential slit spacing is 3-4cm.(3)Overdrilling holes in the middle of the cutting are used layout of "Plum type",which can improve the cutting blasting footage effectively.But the vibration is larger.(4)With longitudinal slotted pipe charging,peripheral holes has obvious directional fracturing effect.Compared with the general smooth blasting,they can obviously reduce the single hole charge and the hole density coefficient. |
