Full-scale physical testing of a buried reinforced concrete pipe under axle load

Abstract

The structural response of a 600 mm inner diameter reinforced concrete pipe buried in a dense, well-graded sand and gravel soil and subjected to surface load from a single design truck axle with 0.3, 0.6, and 0.9 m of soil cover above the pipe crown is quantified using full-scale physical testing. The pipe did not crack at its minimum burial depth of 0.3 m under working CL-625 and CL-800 single-axle highway design loads as the largest tensile strains were only 50%–60% of those at the onset of cracking. Application of the fully factored CL-625 single-axle load at a burial depth of 0.3 m resulted in a tensile crack and a maximum circumferential bending moment of 6 kN·m/m; however, no limit state was reached as the crack width was around one-half the value used to define pipe serviceability and the maximum moment was around 70% of the theoretical ultimate capacity. The decrease in pipe demand from surface load with increasing soil cover is also quantified. At 400 kN of single-axle force, the crown moment decreased to 65% and 35% of the value at 0.3 m burial when the depth of soil cover was increased to 0.6 and 0.9 m, respectively.