Centrifuge Test to Evaluate the Geotechnical Performance of Anchored Buried Pipelines in Sand

The aim of this study was to evaluate the uplift capacity of buried pipes to propose a new anchoring system using geogrids as an alternative and to improve the uplift resistance and inhibit the upward movement of pipes, which can compromise pipeline operation. The simulation was performed in a general scale model of 1/10 using the geotechnical centrifuge of the State University of Norte Fluminense (UENF) at 10 times earth gravity acceleration to keep the similitude between the prototype and the model. The tests were carried out for two different sand densities, two geogrid widths, and three burial depths. The geogrid was manufactured in a laboratory to mimic the behavior of a real-scale geogrid when subjected to upward displacements. Therefore, an amount of 24 pullout tests were conducted in small-scale models at 10 g. A pipe of outer diameter D was anchored to a geogrid with a width of 2D in six tests and to a geogrid with a width of 3D in six other tests. No anchoring system was used in 12 tests; the pipe was simply buried in sand. Standard sand at two different relative densities (23 and 70%) was used as backfill material. The results revealed improvement in the uplift normalized resistance for pipes anchored to the geogrid, especially for those at shallow burial depths. The postpeak (large displacement) behavior was highly improved, which will allow the pipe to withstand considerable displacements without loss of resistance. This is of particular importance when the pipeline is installed in sites where the groundwater table is high.