Evaluation Of Loess Collapsibility Along Xinjiang Coal Gas Pipeline And Stability Simulation Of Slope Laying Pipelines

Coal gas pipeline of Xinjiang project passes through the Xinjiang,Ningxia,Gansu,this area is an important area of loess distribution in China,especially,the project has traversed large collapsible loess areas along the line.The collapsible Loess will cause serious harm to the construction and operation of pipeline engineering because of its special structure,especially bury pipeline in a slope,the pipeline is often exposed and suspended,causing the pipeline to break and cause huge economic loss.Therefore,it is the great significance to study the collapsibility distribution of the pipeline and analyze all kinds of problems about burying pipeline in a slope.This paper takes the Coal gas pipeline of Xinjiang as the engineering background,We have conducted field investigation and sampling,indoor test and so on in the early stage,and studied the distribution characteristics of the collapsible Loess in Ningxia Guyuan and Zhongwei City and Pingliang section of the pipeline.We systematically analyzed the genesis of the Loess and factors of affecting the collapsibility of Loess in the study area.And in the paper,we based on mechanical analysis and calculation,and established mechanics model,combined with the similarity simulation experiment,analysis the effect of water flow on oil and gas pipeline where buries pipeline in a slope with different angles,By the numerical simulation calculation,analysis the force of pipeline after hanging in different angle of slope.Finally,we put forward the prevention measures and suggestions for the Loess of the study area.Through investigation,analysis and research,it is known that the formation of the Loess in the study area is mainly caused by the Aeolian and alluvium.The Aeolian Loess is mainly developed in the Loess Ridge,Hills and Gully,the alluvial Loess is mainly developed on the I and II terrace of JingHe,NaHe,Hei He,DaxiHe River,and ShiJiaGou's river valley.On the basis of field investigation and sampling,We have carried out the evaluation of the collapsibility of the Loess and analysis the factors of affecting collapsibility of Loess in the study area.We obtained the collapsibility of loess in Guyuan,Zhognwei and Pingliang,and analyzed the correlation between collapsibility and topography,loess clay content,water content and void ratio.We based on the principle of physical similarity and FLAC^3D simulation software,we have carried out physical similarity simulation and numerical simulation calculation.Through the physical similarity simulation,We have obtained the relationship between the stability and the slope angle of the pipeline under the influence of water flow.With the increase of the slope angle,the damage of the flow to the pipeline is more and more serious.When the angle of the slope reaches 50degrees,it reaches the peak value.As the angle continues to increase,the damage of the water flow to the pipeline is weakened.Through numerical simulation,it is concluded that after the pipeline is damaged,the pipeline will move along the suspended part to the two ends,the force and displacement of the pipeline will be smaller and smaller.When the slope angle is 40 degrees,the pipeline strain is the most serious,when the slope angle is 30 degrees,the pipeline strain is the least.