隧道分岔段爆破掘进技术研究

Research on the Blasting Excavation Technology of Tunnel in Fork Section

研究目的:隧道分岔段因两条单线隧道的中隔岩墙间距非常小,后行隧道爆破掘进后中隔岩墙两面临空,不当的爆破扰动可造成中隔岩墙严重损伤,甚至造成安全事故,因此需要研究适合隧道分岔段爆破掘进方法。研究结论:(1)结合某铁路隧道分岔段钻爆掘进实践,证明Ⅲ级围岩的中隔岩墙最大爆破振动速度不超过20 cm/s是安全的;钻爆开挖使2.7 m厚中隔岩墙两侧临空后,各侧有0.65~0.9 m的松动损伤区;后行隧道爆破开挖后中隔岩墙侧向位移量达6 mm,并很快趋于稳定;(2)隧道分岔段采用预留光爆层分部开挖法,对中隔岩墙进行信息化跟踪监测,并按监测数据及时优化爆破方案,这是确保中隔岩墙安全的最有效控制爆破方法;(3)本研究成果不仅可用于隧道分岔段,也可用于两条并列小间距隧道的爆破施工中。

Research purposes:Due to the very small thickness of the partition rock wall between the two single-line tunnels in the fork section of the tunnel,after the blasting excavation of the rear tunnel,the two sides of the rock partition wall are empty.The improper blasting disturbance can cause serious damage to the rock partition and even cause safety accidents.Therefore,the research is required to find suitable measures for blasting in tunnel fork.Research conclusions:(1)Based on the blasting experiments carried on the fork section of a urban railway tunnel,the maximum peak particle velocity should be under 20 cm/s to be safe for the partition of III grade rock mass.There was 0.65 m~0.9 m loose damage zone on each side of a 2.7-metre-thick rock partition with two free surfaces caused by the blasting excavation.The lateral displacement of the rock partition approached 6 mm after the blasting excavation of the rear-tunnel and tended to be stable in short time.(2)The experiments proved that the preserved smooth blasting layer excavation method is used along with digital tracking and monitoring on the rock partition,in order to adjust and optimize the plan based on the data,which is the most efficient control blasting measure to ensure the integrity of rock partitions in tunnel forks.(3)The research results can be used not only in tunnel fork but also in two parallel tunnels with small spacing by blasting excavation.