高墩简支渡槽逐跨延期双向定向倒塌爆破拆除

Study on Span-by-span Delay Bidirectional Blasting Demolition for Simply Supported Aqueduct with High Piers

为了顺利爆破拆除宜昌市东风渠75#~84#槽墩之间的高墩钢筋混凝土渡槽时降低对周围复杂环境的影响,采用了双方定向倒塌的方案。即:75#~76#槽墩之间渡槽垂直于渡槽走向朝北定向倒塌,77#~84#槽墩沿着渡槽走向朝西定向倒塌。以75#槽墩为起爆点,使用电子雷管与非电雷管相结合的爆破网路,并设置墩柱之间延时分别为50 ms和150 ms。同时利用吊装孔作为炮孔、开挖减振沟、挂网及覆盖防护、槽身蓄水、覆土防护等措施以降低爆破有害效应对环境的影响。结果表明:起爆后渡槽延迟4分钟倒塌,倒塌后的墩身基本分解为砌块,多数砌块及槽身保持完好;沿走向倒塌的渡槽绝大多数散落砌块及破碎体散落在距渡槽走向中轴线10 m范围内,仅少量小块碎石飞出10 m外。采取的多重防护措施有效控制了爆破飞石和爆破振动,需重点保护的倒虹吸临时输水管道和下穿公路路面等未见损坏。尽管有延迟倒塌的瑕疵,该工程仍算成功实施。延迟倒塌的可能原因为未对切口外构造柱弱化或切割处理、墩柱间爆破延期时间间隔偏小和爆破切口偏小。

In order to successfully demolish a high pier reinforced concrete aqueduct by blasting between the 75#~84#piers of Dongfeng Canal in Yichang City and reduce the impact on the surrounding complex environment,a bidirectional collapse design was adopted.In the design scheme,the aqueducts between the 75#~76#piers collapse in a northerly direction perpendicular to the aqueduct trend,and the aqueducts 77#~84#piers collapse westward along the aqueduct trend.More precisely,an initiation network of electronic and non-electric detonators with delays of 50 ms and 150 ms was adopted using the 75#pier as the initiation point.Moreover,the harmful effects of blasting on the environment were controlled by using lifting holes as blast holes,excavating vibration reduction ditches,hanging nets and covering protection layer,storing water in the trench body,and covering soil protection.The results show that the aqueduct collapsed with a 4-minute delay after initiation,and the collapsed pier body was basically decomposed into blocks with intact aqueduct body,with most fragments scattered along the trend within 10 m of the central axis of the aqueduct,and only a few small pieces flying farther than 10 m.The adopted protective measures can effectively control the blasting flying rocks and vibration,and no damage has been found to the inverted siphon of temporary water delivery pipeline and the road pavement.The project was carried out successfully despite the delay in collapse.The possible reasons for the delayed collapse include no incision on outside of the structural column,the delay time interval between pier columns is small,and the blasting incision is small.