Based on the Guizhou section of Shanghai-Kunming passenger tunnel engineering of drainage tunnel under the railway tunnel,the excavation of the drainage tunnel with ultra-small distance of 0.5 m is carried out.The construction progress,blasting vibration,blasting damage and other influencing factors were analyzed.The preset vibration protection structure combined with the numerical simulation was proposed.The vibration response of the blasting was measured timely.The allowable synthetic vibration velocity 10 cm/s was taken as the warning vibration threshold.Real-time adjustment of the fine blasting design was taken and the construction was combined with the latter part of the monitoring.The results showed that he fine blasting vibration reduction technology can ensure the safe operation of the existing tunnels when the drilling is carried out with 0.5 m ultra-small clearance.It can provide a reference for similar blasting excavation control of tunneling projects.%依托沪昆客专贵州段小高山隧道泄水洞下穿铁路隧道正洞工程,针对泄水洞0.5m超小净距爆破开挖下穿既有铁路隧道,对施工进度、爆破振动、爆破损伤等影响因素深入分析,提出采用预设减振保护结构结合数模,现场实时监测爆破振动响应,设置允许合成振速10 cm/s作为预警振速界限,实时调整爆破方案的减振精细爆破设计思路,并结合后期监测等进行施工.结果表明,减振精细爆破设计在下穿钻爆施工中,能有效保证0.5m超小净距下穿既有隧道的安全运行,该工程的成功实践,可为类似下穿隧道工程的爆破开挖控制提供参考.
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