Compaction effects on strains within profiled thermoplastic pipes

Abstract

Results from laboratory tests are reported to establish how pipe deflections, strains and local bending are influenced by the selection of backfill soil and its placement for two profiled thermoplastic culverts. Lined-corrugated high-density polyethylene (HDPE) and poly vinyl chloride (PVC) pipes with a nominal inside diameter of 600 mm were tested in poorly graded sand and well-graded gravel backfills. The backfill was compacted using real compaction equipment and procedures, and then subjected to a maximum increase in vertical pressure of 200 kPa in a test cell that simulates deep burial. For the specific conditions tested, the largest deflections and strains were for the HDPE pipe when placed just above a rigid base and with uncompacted sand backfill placed below the springline, while local bending was greatest for the PVC pipe with well-compacted gravel backfill. A procedure is presented to account for the maximum local bending strain within a simplified design approach for profiled thermoplastic pipes using an empirical strain factor inferred from the measured results.