拱式渡槽逐跨延期爆破且需保留槽墩时跨间起爆时差的选择

Selection of Initiation Delay Time for Arch Aqueduct Blasting under Condition of Span by Span Collapse and Pier Retaining

大型拱式渡槽爆破拆除工程采用逐跨起爆方案时,跨间起爆时差的选择对其塌落运动状态影响显著。而在保留槽墩的条件下,起爆时差的选择还会影响保留槽墩的损伤程度。以浙江龙门桥渡槽爆破拆除工程为例,建立了渡槽上部结构的动力学方程,确定了失稳拱架的支座反力,以及不平衡支座反力对槽墩产生的力矩,进而建立了槽墩横截面边缘的应力时程曲线计算模型。根据结构自振周期计算模型,计算了拱架与槽墩在起爆后的应力瞬态调整所需时间。分析表明:当槽墩截面不能承受拉应力时,跨间起爆时差应小于拱架与槽墩的应力调整时间之和;当槽墩截面可承受一定的拉应力时,跨间起爆时差可适当延长。根据理论分析结果,确定了龙门桥渡槽爆破工程的跨间起爆时差,且槽墩保护效果良好。

When the span-by-span initiation scheme is adopted in large arch aqueduct blasting demolition project,the selection of the initiation delay time between spans has a significant influence on the collapse motion state.In the case of pier retaining,the initiation delay time can also affect the damage degree of the reserved piers.In this paper,taking the Longmen Bridge aqueduct blasting project as an example,the dynamic equation of a blasted arch is established.Meanwhile,the support forces of arches and the moments of piers are determined.Furthermore,the calculation model for the stress time history curves of piers is established.Finally,according to the calculation model of natural vibration period of the structure,the time required for stress transient adjustment of arche frame and piers after detonation are calculated.The analysis shows that,if the pier section cannot be bear the tensile stress,the initiation delay time between spans should be smaller than the sum of stress adjustment time of piers.Otherwise,the initiation delay time can be extended.According to the results of theoretical analysis,the initiation delay time between spans of Longmen Bridge aqueduct blasting engineering is determined,and the pier protection effect is good.