Performance of Thermoplastic Culvert Pipe Under Highway Vehicle Loading

DOTs are interested in developing guidelines for use of large diameter corrugated HDPE pipe buried under roadways with shallow fill, but this application has not been studied extensively. A pooled fund study consisting of full-scale field tests and computer modeling has been initiated to address this matter. The objectives of the project are to improve understanding of the behavior of large diameter thermoplastic culverts under low fill heights, and develop design and installation procedures for inclusion in DOT and AASHTO specifications. The field tests are being conducted at the MnRoad Research Facility, which maintains a two-lane test road traversed only by test vehicles, a truck with a maximum axle load of 107 kN (24,000 lb) travels in one lane and a truck with 80 kN (18,000 lb) maximum axle load travels in the other. Ten 20 m (65 ft) runs of 1,500 mm (60 in.) diameter test pipe were installed. Test pipe consisted of eight runs of thermoplastic pipe, and one run each of reinforced concrete and corrugated steel pipe. Nominal installation depths were 0.3 m and 0.6 m (1 ft and 2 ft) to the top of pavement. Backfill materials were A-1 and A-2 soils per AASHTO M145. Backfill compaction effort was minimal. Pipes were instrumented with strain gages, displacement transducers, soil pressure cells, and thermocouples. All instruments are connected to dataloggers that are remotely accessed via an internet connection. This paper reports on the installation of the test pipe and early results on pipe performance. Deflections and strains are small. There has been some settlement in the backfill due to the low compaction levels.