Laboratory Investigation of Buried Pipes Using Geogrid and EPS Geofoam Block

This paper describes the results of laboratory tests conducted on flexible PVC pipes with diameter of 160 mm, buried in unreinforced and reinforced trench with geogrid layer and expanded polystyrene (EPS) geofoam block. The repeated load with amplitude of 450 kPa and frequency of 0.33 Hz was applied on the trench surface, using plate loading at a diameter of 150 mm to simulate the vehicle loads. Vertical diameter strain (VDS), strain at pipe's crown and transferred pressure on the pipe's crown were recorded throughout the test for up to 500 cycles of loading. The variables examined in the testing program include thickness of EPS block (30, 60 and 100 mm) and its density (10, 20 and 30 kg/cm3). The pipes were embedded at depths 1.5 times their diameter and the width of EPS block was kept constant at 2.0 times the pipe diameter in all tests. The results show that the values of VDS and pipe strain increased rapidly during the initial loading cycles, thereafter the rate of deformation and strain reduced significantly as the number of load cycles increased. According to the results, the minimum VDS and pipe's crown strain were provided by 100 mm thickness and 30 kg/cm3 of EPS block placed over the pipe with a geogrid layer giving values of, respectively, 0.15 and 0.10 times those obtained in the reinforced trench with a geogrid layer.