复杂环境下钢筋混凝土箱形拱桥的拆除爆破技术研究
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摘要
某待拆大桥为钢筋混凝土结构,拱肋采用箱型截面的混凝土箱形拱桥,经多次加固,桥面到墩角最高45m,拱箱壁为薄壁结构。传统钻爆方式无法有效破坏其结构。同时,大桥右岸桥头两侧与房屋紧邻,均为砖混结构,最近处相隔仅1.8m。右岸桥头东侧20m为交通局路政大队,桥台基础与路政大队房屋基础位于同一基岩上。大桥上游平行5m远处,有架空过江污水管,管径为20cm,与桥面垂直高差8m。采用水压和浅孔爆破相结合的方式,桥面、拱上结构等用浅孔爆破。同时,对大桥东侧与相邻房屋同基岩的拱座基础2m范围内,在拱脚根部采用弱松动爆破(混凝土破碎未脱笼,避免损伤拱脚基岩),形成1m宽力学铰(类似橱柜门的"铰链"),在大桥中间段爆破后,使得剩余结构有围绕"铰链"向中部倾倒的趋势;在"铰链"上,沿拱肋5~10m位置,再采用完全爆破方式(混凝土粉碎,脱离钢筋笼)布孔,在"铰链"位置起爆750ms后,最后起爆,确保房屋基础不受扰动。大桥解体充分,空气冲击波、飞石及噪声等得到有效控制,也减少了后续出渣工作量。该爆破拆除技术可为类似项目提供可靠的爆破设计和施工参考。
A bridge to be demolished is a reinforced concrete structure, and the arch rib is concrete box-ribbed arch bridge with box sections. After several reinforcements, the bridge top to the pier is 45 m, and the wall of the arch box is thin-wall structure. The traditional drilling and blasting method cannot effectively destroy the structure. At the same time, both sides of the bridge on the right bank are adjacent to the buildings, which are brick-concrete structures, and the nearest separation is only 1.8 m. 20 m to the east side of the bridge on the right bank is the Highway Administration, and the foundation of the abutment is located on the same bedrock with that of these buildings. 5 m away at the upper reaches there is a crossing-river sewage pipe overhead,with a diameter of 20 cm and a vertical height difference of 8 m with the bridge deck. The combination of hydraulic pressure and shallow hole blasting is adopted, and the latter is applied to bridge deck and arch structures. Meanwhile, within the 2 m range of the arch base of the same bedrock between the east side of the bridge and the adjacent buildings, the weak loosening blasting is used in the root of the arch foot(the destroyed concrete is released out to avoid damages to the base rock of the arch foot),and an 1 m wide mechanical hinge(similar to the hinges of the cabinet door) is formed. After the blasting in the middle section of the bridge, the remaining structure is rendered to topple over the middle section embracing the "hinges". On the "hinges", along the position of 5-10 meters in the arch rib,a complete blasting method(concrete is smashed out of the reinforcement cage) is used, and 750 ms of blasting later at the "hinges", the last blasting is done, so the building foundation is ensured undisturbed. The bridge is fully disintegrated,air shock waves,flying rocks and noise are effectively controlled,and the subsequent slag discharge workload is reduced. This blasting design and construction can offer references for similar projects.
A bridge to be demolished is a reinforced concrete structure, and the arch rib is concrete box-ribbed arch bridge with box sections. After several reinforcements, the bridge top to the pier is 45 m, and the wall of the arch box is thin-wall structure. The traditional drilling and blasting method cannot effectively destroy the structure. At the same time, both sides of the bridge on the right bank are adjacent to the buildings, which are brick-concrete structures, and the nearest separation is only 1.8 m. 20 m to the east side of the bridge on the right bank is the Highway Administration, and the foundation of the abutment is located on the same bedrock with that of these buildings. 5 m away at the upper reaches there is a crossing-river sewage pipe overhead,with a diameter of 20 cm and a vertical height difference of 8 m with the bridge deck. The combination of hydraulic pressure and shallow hole blasting is adopted, and the latter is applied to bridge deck and arch structures. Meanwhile, within the 2 m range of the arch base of the same bedrock between the east side of the bridge and the adjacent buildings, the weak loosening blasting is used in the root of the arch foot(the destroyed concrete is released out to avoid damages to the base rock of the arch foot),and an 1 m wide mechanical hinge(similar to the hinges of the cabinet door) is formed. After the blasting in the middle section of the bridge, the remaining structure is rendered to topple over the middle section embracing the "hinges". On the "hinges", along the position of 5-10 meters in the arch rib,a complete blasting method(concrete is smashed out of the reinforcement cage) is used, and 750 ms of blasting later at the "hinges", the last blasting is done, so the building foundation is ensured undisturbed. The bridge is fully disintegrated,air shock waves,flying rocks and noise are effectively controlled,and the subsequent slag discharge workload is reduced. This blasting design and construction can offer references for similar projects.
引文
[1]支文超.580m长钢筋混泥土箱型拱桥爆破拆除[J].爆破,2017(3):100-103.
[2]汪小艳,宋磊,张建仁,等.水压爆破技术在潼南涪江大桥拆除施工中的应用[J].重庆建筑,2017(3):55-56.
[3]汪龙,孟祥栋,杨永刚.三峡四期蓄水清库工程“最后一爆”——涪陵白涛旧乌江大桥拆除爆破[J].重庆建筑,2012(2):44-46.
[4]汪旭光,郑炳旭.爆破手册[M].北京:冶金工业出版社,2010:689,764-771.
[5]赵明生,龙源,贾永胜,等.预应力混凝土连续梁桥控制爆破拆除[J].爆破,2015,32(4):106.
[6]GB 6722-2014爆破安全规程[S].北京:中国标准出版社,2015.
[7]周家汉.爆破拆除塌落振动速度计算公式的讨论[J].工程爆破,2009,15(1):1-5.
[2]汪小艳,宋磊,张建仁,等.水压爆破技术在潼南涪江大桥拆除施工中的应用[J].重庆建筑,2017(3):55-56.
[3]汪龙,孟祥栋,杨永刚.三峡四期蓄水清库工程“最后一爆”——涪陵白涛旧乌江大桥拆除爆破[J].重庆建筑,2012(2):44-46.
[4]汪旭光,郑炳旭.爆破手册[M].北京:冶金工业出版社,2010:689,764-771.
[5]赵明生,龙源,贾永胜,等.预应力混凝土连续梁桥控制爆破拆除[J].爆破,2015,32(4):106.
[6]GB 6722-2014爆破安全规程[S].北京:中国标准出版社,2015.
[7]周家汉.爆破拆除塌落振动速度计算公式的讨论[J].工程爆破,2009,15(1):1-5.