爆破地震波作用下法兰接口燃气管道动力失效机制

基于典型城市燃气管道直埋地层特点，通过全尺寸直埋燃气管道爆破地震实验，并结合LS-DYNA动力有限元数值计算软件建立不同爆源距离的无接口和法兰接口的燃气管道模型，分析研究了爆破地震波作用下法兰接口燃气管道动力响应特征及其失效机制。研究结果表明:管道截面应变以轴向拉伸应变为主，环向应变为辅；不同爆破工况下，无接口管道和法兰接口管道及地表峰值振动速度随爆源距离减小而增大；沿管道轴线方向，无接口管道、地表峰值振动速度以管道中心截面为对称面沿两端不断减小，法兰接口管道峰值振速由两侧向中间逐渐增大，在法兰接口处突然减小；法兰接口处出现明显的应力集中现象；管道法兰接口处是爆破地震作用下研究的关键点，螺栓的峰值有效应力、垫片轴向压力、法兰峰值有效应力、法兰偏转角随爆源距离增大而减小；法兰管道偏转角与地表峰值振动速度具有对应关系，法兰接口燃气管道中心正上方地表的控制振速（13.82 cm/s）可作为邻近燃气管道爆破工程地表的安全控制值。

Dynamic failure mechanism of gas pipeline with flange joint under blasting seismic wave

In the process of blasting and excavation of urban subways, controlling the impact of blasting vibration on adjacent pipelines is critical. Based on the characteristics of directly buried gas pipelines in Wuhan and the full-scale direct-buried gas pipeline blasting seismicexperiment, the dynamic finite element numerical calculation software LS-DYNA was used to establish gas pipeline without joints and flange gas pipeline models under different blasting source distances. The effects of blasting seismic wave’s dynamic response characteristics of flanged gas pipeline were analyzed. The research results show that the strain of pipeline section is mainly axial tensile strain, supplemented by circumferential strain. The peak particle velocity of pipeline without joints and flange pipes and the ground surface increase with the decrease of the distance from the blasting source under different blasting conditions. Along the pipeline axis, the peak vibration velocity of the pipeline without joints and the ground surface decreases along the two ends with the central section of the pipe as the symmetry plane. The peak particle velocity of the flange pipeline gradually increases from two sides to the middle but suddenly decreases at the flange joint. There is an obvious stress concentration at the flange interface. The flange joint is the key point of pipeline under blasting earthquake. The peak effective stress of the bolt, the axial pressure of the gasket, the peak effective stress of the flange, and the flange deflection angle decrease with the increase of the explosion source distance. The deflection angle of the flanged pipeline has a corresponding relationship with the peak vibration velocity of the ground surface. The control vibration speed of 13.82 cm/s on the surface directly above the center of the flanged gas pipeline is used as the safety control value of the adjacent gas pipeline under blasting engineering.