立体交叉石拱桥爆破拆除振动危害控制

Vibration Hazard Control of Blasting Demolition of Interchange Stone Arch Bridge

纳雍维马石拱桥与简支梁新桥水平方向呈41°斜交,全长为68 m,从新桥第5跨下28.5 m穿过,距新桥4#立柱仅0.8 m。为确保紧邻既有桥梁顺利的爆破拆除,采用原地缓冲塌落控制爆破技术来确保紧邻既有桥梁安全。根据石拱桥自身结构特点,爆破拆除石拱桥对周围环境的破坏,尤其是对4#立柱和墩基础的危害,我们进行了爆破和塌落振动分析,工程中采取了喇叭型爆破切口、上移东西拱脚爆破切口至第二腹拱、增加靠近4#立柱破碎切口、采用起爆网路时差“由西向东、由南向北”顺序,调整靠近4#立柱炮孔抵抗线、各个爆破切口采用不同的炸药单耗等方法,来实现石拱桥爆破拆除有向南倾倒的趋势的同时,满足塌落体最小化以及减小爆破对周围环境的影响,并利用渣石和软土堆码缓冲减振堤、搭设防护排架等安全防护措施,确保了石拱桥爆破拆除的可靠性和安全性。利用塌落振动公式计算新桥4#立柱对应桥面振动速度为3.9~5.2 cm/s,与测振仪测得该点最大振动速度3.879 cm/s相近,验证了爆破拆除石拱桥设计思路及相关参数的选取是科学、合理的。爆破拆除取得理想的效果。

Nayong Weima stone arch bridge and the new simply supported beam bridge have a 41°diagonal crossing in the horizontal direction,with a total length of 68 m.It passes 28.5 m below the fifth span of the new bridge,and is only 0.8 m away from the#4 column of the new bridge.In order to ensure the successful blasting demolition of the old stone arch bridge,the in-situ buffer collapse control blasting technology is adopted to ensure the safety of the adjacent new bridge.Considering the damage to the surrounding environment caused by the blasting demolition of the stone arch bridge,especially the damage to 4#column and the pier foundation,the horn blasting notches is used based on the structural characteristics of the stone arch bridge and the analysis of blasting and collapse vibrations.At the same time,the blasting notch of the East-West arch foot is moved to the second abdominal arch,and the crushing notch close to#4 column is added.For the initiation network,the sequence of"west to east and south to north"is adopted.Other methods include adjusting the resistance line of the blast hole close to the#4 column and taking different powder factors for different blasting notches,etc.All those measures are taken to make the stone arch bridge tends to collapse to the south with a minimum collapse size and reduce the impact of blasting on the surrounding environment.Furthermore,the reliability and safety of the blasting demolition of the stone arch bridge are ensured by the safety protection measures such as stacking of slag and soft soil to cushion dikes and setting up protective shelving.According to the collapse vibration formula,the vibration velocity of the bridge deck corresponding to the#4 column of the new bridge is calculated to be 3.9~5.2 cm/s,which is close to the maximum vibration velocity of 3.879 cm/s measured by the vibration meter.It is verified that the design idea of the blasting demolition of the stone arch bridge and the selection of the relevant parameters are scientific and reasonable.The blasting demolition has achieved ideal results,which could provide reference for similar blasting demolition projects.