Research On Residual Strength Evaluation Technology Of Gas Pipeline Containing Volume Defects Under Landslide

With the development of the economy and the adjustment of energy structure,China's natural gas consumption is rising gradually.In 2017,the consumption was 237.3 billion cubic meters,and it is expected to reach 500 billion cubic meters by 2030.Energy sources are concentrated in the central and western regions while energy consumption is concentrated in the east.Therefore,long-distance transmission of natural gas is required.At present,the long-distance transport of natural gas is mainly carried by long-distance pipelines.China has a vast territory and complex geological conditions.The long-distance pipelines will inevitably cross the landslide geological disaster area.At the same time,due to pipeline service time and environmental factors which caused defects in pipelines,the safety of pipelines with defects will be reduced when pass through the landslide disasters area.Therefore,it is of great significance to study the residual strength of the defective pipeline under the effect of landslides.In this paper,ABAQUS simulation software is used to evaluate the residual strength of gas pipelines with volumetric defects under the effect of landslides.The main research contents and achievements are as follows:(1)This paper systematically investigates the domestic and foreign research methods on the mechanical response of the pipeline under the effect of landslides,and the theoretical calculation method and numerical calculation method are compared in detail.The results show that the numerical calculation method is reliable and easy to be realized,therefore,the numerical calculation method is adopted in the follow-up study.(2)Based on the material nonlinearity and contact nonlinearity,a finite element model for the mechanical response analysis of pipeline under landslide is established and the model calculation was completed.Combined with the relevant experimental blasting data,the finite element model of the volumetric defect pipeline under the internal pressure was established(including spherical model and uniform wall thickness model).Compared with the experimental blasting data,it was found that the geometric model of the volumetric defect was closer to the blasting test data when the uniform wall thickness model was used.(3)Combining with the finite element model of the pipeline under the effect of the landslide and the finite element model with the volume-defective pipeline,the finite element model for evaluating the residual strength of the volume-defective gas transmission pipeline under the effect of the landslide is established,and the tube-soil nonlinearity is considered.On the basis of nonlinear contact of pipe and soil and nonlinear contact of soil and soil,the residual strength evaluation of a pipe with volumetric defects under the effect of landslide was evaluated.(4)Based on the evaluation of the residual strength of the pipeline with volumetric defects under the effect of landslides,the influences of landslide displacement,defect size,axial position of the defect,buried depth of the pipeline,soil quality and internal pressure of the pipeline on the residual strength values were studied.Then,the single factor analysis of each factor was completed by the control variable method,and the stress calculation single factor correction coefficient of related influencing factors was introduced in combination with the ASME-B31G criterion.(5)Taking a landslide accident with a defective pipeline in our country as an example and combining it with a two-dimensional homogeneous slope model to evaluate its residual strength,the results show that the pipeline can still operate safely,in accordance with the actual situation,and the correctness of the residual strength evaluation finite element model is also verified.