The Strain Based Design Of X80 Steel Pipeline Under Geological Disasters

The terrain is varied of our country, and geological disasters often occur. Especially in recent years, environmental degradation, natural disasters such as landslide, debris flow, all these caused serious threat to the oil and gas pipeline transportation safety. Large displacement of soil caused by landslides can cause pipe bending, and lead to serious pipeline rupture. The falling rocks caused by Landslides did a direct impact of the pipe, can cause pipeline instantaneous destruction. X80 steel has the characteristics of sustain deformation, has been widely applied in the construction of long distance oil and gas pipelines. Therefore it is of great significance in researching the strain law of the X80 steel pipeline under geological disaster.This paper discussed the damaging effects of landslides and rockfall impact generated by the pipeline to explore the factors that affect the safety of the pipeline, mainly to do the following work areas:This paper mainly analyzed the destructive influence on pipeline caused by landslide and rockfall, and the factors which affected the safety of pipeline. The main aspects of the following work can be concluded as follows.At first, the buried pipe under the two installation modes of soil mechanics model is analyzed, and the vertical and lateral earth pressure formula of the conventional buried pipe are summed up, different buried pipe mechanical characteristics have been got. Comparing the advantages and disadvantages of the existing soil-pipeline interaction model, this paper decided to use the finite element soil-spring model to analyze the pipe strain. This paper through the analysis of an example obtained the rules of the pipeline axial strain under landslide. And analyzed the difference of the pipeline’s landslide strain resistance between the pipeline with internal pressure and without internal pressure. Several factors which affect the safety of pipeline under the action of landslide were considered. Such as pipe diameter, thickness ratio of landslide decline in width, depth, Angle of internal friction of soil and pipeline internal pressure. The Results show that the axial strain of the pipeline with internal pressure than the pipeline without internal pressure when large displacement occurs. The maximum strain is in the landslide section of middle position, followed by landslides and the landslide section at the junction. The maximum strain is at the position of the middle of the landslide and the position of the landslide and non-landslide junction.In addition, the process of the rockfall impacting pipeline was simulated by the LS-DYNA finite element software. The changing rules of the pipe stress and strain under the action of spherical and square rockfall, in different time, were analyzed. Come to the conclusion that square rockfall linear impact pipe on one side, more secure than the spherical rock fall. The factors include the pipe diameter thickness ratio, rock fall impact Angle, and the size of the rock fall, and impact velocity that affect the pipeline strain were analyzed. The results show that the smaller pipe diameter thickness ratio while the rockfall impact bear ability stronger; When the rockfall and pipeline impact Angle is 90 °, the pipe would produce the largest strain, at this point the pipeline was in the most dangerous situation; The pipeline axial strain increase linearly with the increase of the rockfall speed. The greater the rockfall speed the pipeline axial strain increases faster.According to the theory and numerical simulation analysis of this article, VB2010 was adopted to prepare the pipeline security software. The main functions include the stability of the buried pipeline under the action of checking, landslides, the analysis of pipeline stress and strain and rockfall impact force calculation.