A semi-empirical model for peak strain prediction of buried X80 steel pipelines under compression and bending at strike-slip fault crossings

• We propose a simple FE model with the advantage of short time consumption and high precision.
• We study the effects of all parameters on the strain quantitatively, especially the soil parameters.
• We derive the peak compressive strain of buried X80 steel pipelines for over 1200 cases.
• A semi-empirical model for predicting the peak compressive strain is proposed.
• The method can be referenced to the strain-based and reliability-based design of X80 pipes under ground movements.

The strike-slip fault is a main type of permanent ground deformation (PGD) faced by long distance gas pipelines. Based on the non-linear finite element method, a numerical model for buried pipelines at strike-slip fault crossings under compression combined with bending was proposed at first. The model, with the advantages of reduced time consumption and high precision, was proven to be reasonable by comparing the numerical results with previous researchers' experiments and numerical results. The peak compressive strain of X80 steel pipelines subjected to strike-slip fault displacement under compression combined with bending was studied using the FE model. According to the investigation of the Second West to East Gas Pipeline Project, suitable ranges of all parameters, including the pipe diameter, wall thickness, soil properties, fault displacement and crossing angle, were obtained. The influence of these parameters on the peak compressive strain was discussed in detail. A regression equation for predicting the peak compressive strain of X80 steel pipelines was derived based on approximately 800 numerical results and regression analysis, and the applicable range of the formula was given. 15 true design cases of the Second West to East Pipeline Project in China were investigated to demonstrate the accuracy and applicability of the proposed methodology by comparing the predicted peak compressive strain results with the FEM results. It was shown that the proposed semi-empirical model predicts the peak compressive strain with good accuracy much less time consumption. It is thus applicable for the strain-based and reliability-based design of X80 steel pipelines subjected to strike-slip fault displacement.