عنوان مقاله [English]
With increase in cities' population and development of urbane life, passing
buried pipelines near the ground's surface is inevitable in urban areas, roads,
subways and highways. In this paper, the results of laboratory tests on flexible pipe with a 160 mm diameter, placed in reinforced-trench by a geogrid layer and an EPS geofoam block subjected to repeated load are investigated. The pipe diameter change, strain and pressure acting over the pipe were measured throughout the loading, unloading and reloading. The parameters inspected in
the tests included the thickness (30, 60 and 100 mm) and width (160 and 240 mm) of EPS block and burial depth of pipe (1.2 and 1.5 times the pipe diameter).
Based on the results, the values of the pipe diameter change and pipe strain
swiftly increases during the early cycles of loadings and followed the stability trend with the gathering of load cycles. In the geogrid-reinforced system, the change in pipe diameter and in pipe's strain at the end of the loading cycles showed 19\% and 20\% reduction, respectively, as related to the unreinforced system. According to the results, the minimum pipe diameter change and pipe's strain were acquired by using EPS block with maximum width, thickness, and 30 kg/m3 density over the pipe in addition to a geogrid layer representing values of, respectively, 0.26 and 0.3 times of the others acquired in the reinforced trench with a geogrid layer.