隧道爆破下底部脱空埋地输气管道的动力响应

Dynamic Response of Buried Gas Pipeline with Partially Bottom Empty under Tunneling Blasting Vibration

以下穿兰成渝输气管道的仙女岩隧道爆破为背景,建立包括管道脱空区在内的隧道爆破三维动力有限元模型,研究爆破地震波引起的不同脱空长度下埋地输气管道的动力响应规律。结果表明:埋地管道下部脱空时,爆破振动作用下管道底部的振速峰值和位移峰值均大于管道顶部,且二者沿管道轴线以脱空中心为对称点呈逐渐减小的趋势;随着脱空长度增大,管道最大振速呈较慢的降低趋势,但最大振动位移却呈较快的增大趋势;爆破振动下管道有效应力峰值和最大主应力峰值出现在脱空中心附近的管道底部,且两者均随管道纵向脱空长度的增大几乎呈线性增大;在管道内压6 MPa及隧道埋深40 m、单段最大装药量17 kg的爆破振动作用下,脱空长度为5 m时爆破振动对管道安全不构成影响,当长输天然气管道在10~12 MPa的高压运行时,爆破振动会降低管道的安全储备。

Based on Xiannüyan tunnel blasting engineering of the high-speed railway from Xi’an to Chengdu passing through a buried gas pipeline, the 3-D dynamic finite element model for tunnel blasting including the empty zone of the pipeline was established. Under the action of blasting seismic waves, the dynamic response law of buried gas pipeline with different lengths of empty caused was studied thoroughly and comprehensively. The results show that when there is clearance between the lower part of the buried pipeline and the surrounding soil, the peaks of vibration velocity and displacement at the bottom of the pipeline are greater than that of the top of the pipeline and these two parameter values are gradually decreasing along the axis of the pipeline with the center point of the empty zone as the point of symmetry. With the increase of the length of empty zone, the maximum vibration velocity of the pipeline decreases slowly, but the maximum vibration displacement shows a rapid increase. Under the blasting vibration, the peaks of the effective stress and the maximum principal stress occur at the bottom of the pipeline near the center of the empty zone and both of them increase almost linearly with the increase of the length of the longitudinal empty zone of pipeline. Under the condition of the operating internal pressure 6 MPa and the tunnel depth 40 m as well as the maximum charge per delay interval 17 kg, when the length of the empty zone is 5 m, the blasting vibration does not affect the operation safety of the pipeline. When the long-distance gas pipeline is operated at a high pressure of 10~12 MPa, the blasting vibration will reduce the safety reserve of the pipeline.