Mechanical Performance Analysis And Seismic Isolation Study Of Cross Fault Buried Gas Pipeline

Due to the distribution characteristics of oil and gas resources in China,pipeline transportation has become an important means of natural gas transportation in China.The total length of trunk pipelines in China has exceeded 200,000 kilometers.A large number of active faults are distributed in China.With the laying of a large number of buried gas pipelines,many buried gas pipelines built or under construction are threatened by near fault dislocation.The environmental conditions of buried gas pipelines are becoming more and more complex.Many gas pipeline projects pass through or are located in the fault dislocation area,and the stress of buried gas pipelines changes accordingly.Therefore,it is necessary to analyze the mechanical properties of buried pipelines under different conditions.Especially for the state analysis of buried pipelines under the movement of large deformation sites such as faults,it is of great significance to prevent the leakage of buried pipelines,increase the ability of buried pipelines to resist disasters,and ensure the smooth operation of pipelines during disasters.This paper mainly completed the following research work :(1)Considering the contact nonlinearity between the pipeline and the soil during the fault dislocation process,a pipe-soil nonlinear contact model with a size of 20 m × 20 m × 180 m is established.In order to accurately reflect the local buckling deformation that may occur after the pipeline is subjected to the fault,the shell element is used to draw the buried pipeline.(2)Taking strike slip faults as the research object,the deformation law of buried pipelines under fault action is analyzed.Buried pipelines mainly fail due to compression buckling under strike slip faults.Among various influencing factors,pipeline wall thickness has the most significant improvement on the mechanical properties of buried pipelines.The critical displacement of pipelines increases exponentially with the increase of pipeline wall thickness.The critical displacement of pipeline faults with a 22 mm wall thickness is 4.9 times that of pipelines with a 6mm wall thickness;High grade steel pipelines can be used to improve the mechanical properties of pipelines.Compared to X56 pipelines,X80 pipelines have a 39%increase in critical displacement of faults;When the pipeline diameter exceeds 800 mm,the mechanical properties of the pipeline are almost no longer affected by the pipeline diameter;The deeper the pipeline is buried,the relative decrease in the critical displacement of the fault.The critical displacement of buried pipelines with a depth of 2.4m is 20% lower than that of pipelines with a depth of 1.6m.For every 0.2m increase in pipeline burial depth,the critical displacement of the fault decreases by 5%,and the pipeline’s ability to resist fault damage decreases.(3)This article uses sand core rubber isolation bearings for seismic isolation design of buried pipelines,and analyzes their isolation effect.It is found that the acceleration response after isolation is 0.495 before isolation,and the acceleration isolation effect of buried pipelines reaches over 50%.The response isolation device has good isolation effect.The research results are intended to provide reference for the isolation design of buried pipeline engineering.