Field Installation Effect on Steel-Reinforced High-Density Polyethylene Pipes

Abstract

A full-scale field study was conducted in Kansas to investigate the installation effect on steel-reinforced high-density polyethylene (SRHDPE) pipes. Four 2.13 m-long SRHDPE pipes with a diameter of 0.61 m were connected and buried in a trench with dimensions of 1.52 m wide, 9.15 m long, and 1.40 m deep. Two types of backfill material were used in the trench, namely, Aggregate Base Class 3 (AB3) aggregate and crushed stone. Two pipes were buried in the AB3 aggregate section with an average degree of compaction of 90.4% whereas the other two pipes were installed in the crushed stone section with an average degree of compaction of 89.5%. The soil cover thickness in both the AB3 aggregate and the crushed stone sections was 0.65 m. A vibratory plate compactor was used to compact the backfill material inside the trench. Pipe deflections in the vertical, horizontal, and 45° directions from the pipe crown were monitored during backfilling. Earth pressures around the pipes were measured during the construction. Test results indicate that (1) the peaking deflection of the pipe in the AB3 aggregate section was 1.5 times that in the crushed stone section; however, the vertical diameter change of the pipe in the crushed stone section was 3.5 times that in the AB3 aggregate section after backfilling above the top of the pipe. The pipe diameter change in the crushed stone section in the 45° direction from the pipe crown was greater than that in the AB3 aggregate section. The deflections of the SRHDPE pipe in these two types of backfill material with a soil cover thickness of 0.65 m were much less than the 5% deflection limit suggested for steel and high-density polyethylene (HDPE) pipes by the AASHTO; and (2) the soil arching factors at the top of the pipe in both sections are greater than one (i.e., negative soil arching). The measured lateral earth pressure data verified that the lateral pressure induced by compaction was constant with depth within the pipe range. The measurement of the displacements of ribs at the springlines of pipes in both sections demonstrated that the ribs in the crushed stone section deformed more than those in the AB3 section. A visual inspection of the exhumed pipes did not find any obvious damage to the pipe ribs and liner. Overall, the SRHDPE pipe performed well in these two types of backfill material during installation.