Study On Mechanical Properties Of Buried Pipelines Crossing Oblique Slip Faults

Long-distance pipeline has the characteristics of high efficiency,convenience and environmental protection.It has become one of the five major transportation means parallel to railway,highway,aviation and water transportation.It is widely used in various aspects of energy transportation,such as oil,natural gas,gas and water.Long-distance pipelines play an important role in guaranteeing economic development,improving people's livelihood,social stability and national defense construction.In recent years,after the completion of the West-East Gas Pipeline,Sichuan-East Gas Pipeline,Central Asian Natural Gas Pipeline,Sino-Kazakhstan Crude Oil Pipeline and Sino-Russian Crude Oil Pipeline,the total length of China's trunk pipeline has exceeded20×10~4km.China is situated in the Eurasian plate and adjacent to the Pacific and Indian Ocean plates.It is one of the countries that suffer the most serious earthquake disasters.A large number of post-earthquake disaster investigations show that many buried pipeline failures occur at active faults,of which the oblique-slip fault is a special type of fault.At present,little research has been done on buried pipelines crossing this type of fault.Therefore,it is of great significance to study the mechanical properties of buried long-distance pipelines across oblique sliding faults for ensuring the safe and reliable operation of long-distance pipelines.In this paper,the mechanical properties of buried pipeline will be studied from the two parts of experiment and finite element.The main research contents and results are as follows:(1)The research status of buried pipelines across faults at home and abroad is summarized,and the research results and development characteristics of theoretical analysis,numerical analysis and experimental research are summarized.(2)Two detachable steel frame earth boxes are designed.Pipes with strain gauges are placed in the soil box,and different types of soil are selected for backfilling.Fault movement is simulated by hydraulic jack and mechanical jack,and strain law of different types of pipelines under different fault offsets is obtained.(3)The finite element model of buried pipeline across oblique slip fault is established by using ABAQUS software.The response of buried pipeline under fault dislocation is simulated,and the corresponding strain and deformation response results are obtained.The results are compared with the test results to verify the validity of the model of buried pipeline across oblique slip fault established in this paper.(4)Based on the finite element model of cross-slip fault,the effects of pipe wall thickness,pipe diameter,pipeline burial depth,soil type and pipeline internal pressure on the displacement,stress and strain of buried pipeline across oblique slip fault are studied.In view of the above factors,the stress and strain response law of buried pipeline under fault dislocation is studied,the peak value and the distribution characteristics of stress and strain are determined,the analysis results are normalized and the simple formula for calculating the pressure and strain of buried pipeline across oblique slip fault under fault dislocation is fitted,in order to provide effective basis for the design and construction of buried pipeline in practical engineering.