Stress Analysis Of Gas Pipelines Passing Through The Yanyingshan Tunnel Of The Seismic Belt

The tunnel crossing engineering is always adopted to cross the complicated mountains for long distance pipeline. Some tunnels may cross seismic area or adjacent to the seismic area inevitably. Stress analysis of gas pipeline crossing seismic area in tunnel should research from two sides of pipeline statics and dynamics analysis. In order to ensure the pipeline operation safely under normal and seismic conditions, stress, displacement and fixed pier stress need to be checked respectively. Gas pipline in Yan Ying mountain tunnel is took as an example in this paper. And related theories of stress and spectrum analysis are used to analyze stress. Based on literature research and analysis, the following work has been carried out:(1) To provide theoretical basis for stress analysi of gas pipeline in Yan Ying mountain tunnel, the basic dynamic load, static load and suitable stress criterions of gas pipeline are determined. Then through analyzing applicability of seismic analysis methods, spectrum analysis method is suitable for this pipeline engineering.(2) Through theoretical analysis and calculation, constraints and boundary conditions of gas pipline in Yan Ying moutain tunnel is determined. Then the gas pipeline model is established by using of CAESAR Ⅱ software. Through analyzing stress and displacement distribution of normal conditions, the dangerous sections of each condition are determined. The stress, displacement and fixed pier stress are checked. Then the results of pipeline stress and displacement are compared under normal conditions.(3) By generating auxiliary calculation program of spectrum curve, the spectrum analysis method is adopted to calculate and analyze spectrum curve. The stress and displacement of pipeline under seismic condition are checked. Through comparing the stress and displacement of the gas pipeline under normal conditions and seismic condition, the key checking condition of the pipeline in tunnel is determined.(4) The factors affecting stress of gas pipline in tunnel are analyzed, including the angle and length of inclined pipline, depth of soil cover, seismic intensity, pipeline pressure and operating temperature, etc. The stress reduction measures are put forward in the area of great stress. By summing up stress analysis results in this paper, some suggestions on seismic design of pipeline in tunnel are put forward from four aspects, including site selection, reasonable design, scientific construction and safety monitoring.In this paper, a complete set of stress analysis method for gas pipeline in tunnel crossing seismic area is formed. The method of modeling based on CAESAR II software provides a method for the designers to build the pipeline model in tunnel. And the understanding and conclusion can provide references for the fine design of pipeline in tunnel. The auxiliary calculation program of spectrum curve can be used to analyze the seismic dynamic analysis of long distance pipeline crossing seismic area.