L52325 Assessment of Geosynthetic Fabrics to Reduce Soil Loads on Buried Pipelines - Phase I and II

High soil loads on buried pipelines can lead to unacceptably high pipeline strains developed in response to permanent ground displacement. Common causes of permanent ground displacement are related to slope instability as a result of heavy precipitation or ground subsidence. In addition, several permanent ground displacement hazards are related to earthquakes including surface fault displacement, triggered landslide movement, surface ground settlement related to liquefaction, and lateral spread displacement. Result: Four specific areas of investigation were completed: 1.Performed baseline tests in moist sand to confirm minimal difference in horizontal soil restraint between moist and dry sand. 2.Performed tests to gauge the variation in horizontal load reduction with separation between the pipe and an inclined trench wall lined with two layers of geotextile. 3.Performed tests in compacted 19 mm (0.75 in) minus sand and crushed limestone (referred to locally in British Columbia as road mulch) to attempt to provide larger difference between horizontal forces developed with and without lining a trench wall with geotextile. 4.Performed tests to attempt to confirm oblique horizontal-axial soil restraint behavior reported in small-scale tests and centrifuge tests. Benefit: Rather than undertake further physical testing to better understand how the presence of single or dual layers of geotextile fabric changes the mechanisms by which soil restraint develops for horizontal ground displacement, future efforts should focus on numerical simulation preferably using discrete element methods. Until full-scale test data are available to confirm consistent prediction of oblique horizontal-axial soil restraint, the practice of treating horizontal and axial soil springs independently in the analysis of buried pipeline response to ground displacement, as is the current practice, should be maintained.