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

Abstract

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.