Experimental evaluation of an expanded polystyrene (EPS) block-geogrid system to protect buried pipes

Abstract

This study presents the results of experimental tests carried on buried uPVC (unplasticized polyvinyl chloride) pipes with an external diameter of 160 mm. The behavior of buried pipes in unreinforced and reinforced trenches by a single layer of HDPE (high-density polyethylene) geogrid and expanded polystyrene (EPS) geofoam block were investigated. To simulate vehicle wheel loadings, 500 cycles of repeated load respectively with an amplitude and frequency of 450 kPa and 0.33 Hz was applied to a loading plate placed over the trench surface. Pipe behavior under cyclic loadings were assessed using vertical diameter strain measurements, circumferential strains and pressures at the crown and springline. Additionally, settlement at the soil surface was measured throughout testing. The testing program is aimed at evaluating the role of different parameters influencing pipe behavior, such as embedded depth of the pipe, implementation of the EPS block and geogrid layer simultaneously and separately, and density, width and thickness of the EPS blocks. The results illustrate that the rate of changes in the pipe circumferential strain, vertical diameter strain and soil surface settlement, which increase rapidly in initial loading cycles, decreased as loading progressed. Based on the results, the density, width and thickness of implemented EPS blocks have an impact role in improving the behavior of buried pipes. The use of geogrid reinforcement with an EPS block with density of 30 kg/m3, thickness of 60 mm and width of 1.5 times the pipe diameter showed the most benefit when balancing vertical diameter strain, pipe crown strain, and soil surface settlement.