Experimental investigation of the effect of geogrid reinforced backfill compaction on buried pipelines response

Abstract

The increasing in development and population, have made using of shallow buried pipelines inevitable in highways, subways, and urban areas. In this paper the behavior and the response of shallow Polyvinyl chloride (PVC) pipes buried in geogrid reinforced sand under static loads was investigated. Three series of large-scale laboratory experiments were conducted under static loading. The first test program investigated the effect of compaction effort on the bearing capacity and surface settlement under static loading of strip footing with no buried pipe. In this testing program six levels of sand relative density were achieved (30%, 40%, 50%, 60%, 70% and 80%). The tests results have shown significant improvement on bearing capacity of soil with decrease in surface settlement. In the second series, a buried PVC pipe with a diameter of 200 mm at a depth of 300 mm was in introduced and loaded with strip loading. In this series of testing the backfill relative density was changed over the same range. The increase in relative density have showed noticeable decrease in surface settlement and load transferred to the pipe crown. Third test series conducted with geogrid-reinforced backfill varying compaction effort above and below the geogrid reinforcement. The highest results have shown the importance of the compaction effort on the installation of geogrid reinforcement. The backfill reinforced with geogrid at relative density of 70% has shown a 78 % reduction in surface settlement, while highest improvement of pipe crown deflection was 51% for 50% relative density. Also, optimum location of one layer of geogrid reinforcement has been investigated. The optimum depth to diameter ratio of the geogrid was found to be 0.11 regardless of the relative density.