Numerical Investigation of Liquefaction Resistance of Buried Pipelines with Sand-Tire Mixture Using Critical State Two-Surface Plasticity Model

Damage to pipelines buried in liquefiable deposits under earthquake loadings has been the main concern for geotechnical engineering in seismically active areas. This paper presents a finite element model of a pipeline buried in the sand-tire mixture under earthquake loading. The sand-tire mixture was modeled by QuadUP elements and a critical state two-surface plasticity constitutive model. Here, we consider Dafalias and Manzari's model for the sand-tire mixture to predict the dynamic behavior of pipelines during earthquake loading. Variation of excess pore water pressure and uplift of pipe during liquefaction of soil are studied using a fully coupled dynamic analysis. Numerical analyzes are performed using the open-source code OpenSees to simulate the pipeline. For verification of the numerical model, simulation of a series of centrifuge tests is conducted and the results are compared with test measurements. The effects of several parameters including different amounts of tire crumb, the percentage of soil relative density, burial depth, the diameter of the pipe and different earthquake time histories are also studied, here. The results show that by increasing tire content in the sand-tire mixture, the excess pore water pressure decreased. Therefore, tire crumbs mixed with sand are useful for decreasing the liquefaction of soil induced floating of buried pipes. Moreover, the parameters such as relative density, optimal depth of buried pipes and pipes diameter have a significant impact on reducing the uplift of pipes.