Preliminary finite element analysis of lateral pipeline/soil interaction and comparison to centrifuge model test results

A problem which has been encountered with the increased use of buried pipelines for carrying gas, oil, water, and electrical cables is the response of the pipeline to soil movements in the vicinity of the pipeline. These movements may be due to adjacent earth works, landslides, thaw/settlement of permafrost, frost heave or a variety of other causes. Soil movements set up stresses within the pipeline, and, depending upon the magnitude of these stresses and the nature of the pipeline, may cause damage to the line. The stresses which are generated by the soil movements are dependant upon a number of parameters, including the nature of the soil, the properties of the pipeline, and the geometry of the pipeline-soil-backfill system. The preliminary results of a finite element analysis of lateral pipeline/soil interaction are presented in this paper. The analysis was conducted using a Finite Element (FE) program to investigate the lateral movement of a pipeline in kaolin clay. The FE analysis can provide data about (1) relationships of forces and displacement of the pipeline; (2) plastic flow/failure zones; and (3) soil failure modes. Results were obtained for variations in the trench depth of the pipeline-soil-backfill system and the undrained shear strengths of backfill and native soils. The preliminary results of this finite element analysis were compared to results from centrifuge model tests conducted to investigate pipeline/soil interaction when the pipeline is subjected to lateral movement of the soil. The centrifuge tests were carried out to investigate specific operational problems where conventional testing and analysis could not provide an explanation for actual problems encountered.