爆炸荷载作用下大跨度动被覆结构荷载分布规律

Distribution law of blast loads on large-span compound structure

为了研究常规武器爆炸作用下大跨度被覆结构的荷载分布规律,首先通过现有经验公式的计算对比,指出了现有公式的适用范围和局限性;其次利用岩(土)中地冲击经验公式,计算得到了不同跨度和不同爆距时环向各点自由场应力的分布规律和峰值应力包络图,并将部分计算结果与数值模拟进行对比,规律基本一致;最后将拱结构环向各点自由场径向峰值应力乘以反射系数,计算得到大跨度动被覆结构径向荷载的分布规律。研究表明,跨度的增加使常规武器爆炸荷载的局部作用效应更加显著,成类三角形分布,结构的荷载形式应简化为三角形荷载。

To disclose the law of blast load changing with lining span,traditional equivalent formula were firstly discussed.Application of the existing equations can not be extended to tunnels with large spans,whose dynamic load under blast can be determined by the product of free field stress and reflection coefficient.According to empirical formulas of the blast free field stress,distribution of the free field stress along the arch surface was calculated.Envelope diagram of the stress looks like a local triangle,especially in larger spans,which further restates the limitation of the traditional equivalent formula of blast load.The dynamic load of large span arches was finally determined by the product of referenced reflection coefficient and calculated radial free field stress,which was also validated by numerical simulations.The research shows that the local effect of blast load was more remarkable with the increase of lining span and the strucure load ditribution must be simplified to local triangle load.