For large cross-section tunnel blasting,the rock mass in the middle of the tunnel face often experi-ences the phenomenon of"bulging"due to the unreasonable arrangement of the cutting holes.In order to eliminate the"bulge belly"phenomenon in large cross-section tunnel blasting,a new method of"wedge cut+high-energy hole"blast hole layout was proposed.Taking the Gonghe Village Tunnel of the Luqiao Expressway in Yunnan Prov-ince as the engineering background,a numerical model of"wedge-shaped cut+high-energy hole"was established u-sing finite element software LS-DYNA.The effective stress at the bottom of the blast hole and dynamic damage of the rock mass were studied and compared with the on-site tunnel cut blasting plan.At the same time,the proposed new method was verified through on-site blasting experiments.The research results indicate that the"wedge cut+high-energy hole"blasting hole layout method can effectively eliminate the"bulge"phenomenon,reduce the number of cut holes and digital electronic detonators,and determine the rationality and applicability of this method.Besides,the stress values generated by measuring points 1,2,and 3 at the bottom of the main cutting hole are relatively small.As the stress sharply rises to 454.9 MPa,the middle-retained rock mass can be effectively broken after the main cutting hole blasted with the high-energy hole explodes.Using the improved blasting method,the excavation efficiency in-creased by 16.9％,the average utilization rate of blast holes reached 91.5％,and the explosive consumption reduced by 19.7％.The proposed layout method of"wedge-shaped cutting+high-energy holes"for large cross-section tun-nels can not only ensure construction safety,but also achieve the effect of reducing costs and improving construction efficiency.
关键词
大断面隧道爆破/楔形掏槽/高能孔/"鼓肚"现象
Key words
large cross-section tunnel blasting/wedge-shaped cutting/high-energy holes/"bulging"phe-nomenon
万方数据