下穿高压铁塔的大跨小净距隧道控制爆破技术研究

Research on Controlled Blasting Techniques for Large-span-small-clearance Tunnels with High-voltage Towers Crossing Underneath

茶山隧道是广东省某高速公路在建的一座大跨小净距隧道,下穿500 kV高压线铁塔,对爆破开挖要求极高。针对该隧道埋深较浅、围岩变化较频繁、长度短的情况,提出全隧道采用短距离三台阶分次爆破开挖方案,即将上台阶单段最大装药量控制在23 kg以内,选择合理的爆破参数,并根据爆破震动监测进行修正,力求隧道爆破时高压铁塔塔基处爆破震动速度不大于2.5 cm/s,以保障隧道上方高压铁塔的稳定和隧道施工安全。该隧道的开挖及爆破方案可为类似工程提供借鉴。

Chanshan Tunnel is a large-span-small-clearance tunnel under construction on some expressway in Guangdong Province with 500kV high-voltage towers crossing underneath,so blasting excavation is highly required.In accordance with shallow buried depth,frequent changes of wall rocks and short length of the tunnel,this paper proposes a scheme of three-step blasting excavation by time in short distance for the whole tunnel,i.e.controlling the max.dosage at single section of upper step within 23kg,selecting reasonable blasting parameters and correcting according to monitoring for blasting vibration in order that the blasting vibration velocity at the foundation of high-voltage towers is not more than 2.5cm/s during tunnel blasting to guarantee stability of high-voltage towers above the tunnel and safety in tunnel construction.The excavating and blasting scheme of the tunnel can provide a reference for similar projects.