An assessment of the performance of corrugated HDPE pipe in shallow fills under railroads

Rail continues to be a major mode of transport in the 21^st century. According to the Association of American Railroads, there were nearly 1.4 million freight cars in service in the United States in 2009, operating on around 140,000 miles of track. As such, it is important to continue to evaluate the different drainage materials that are used underneath railroads. Small diameter corrugated high density polyethylene (HDPE) pipe has been used beneath railroads for decades. Currently, corrugated pipe is manufactured in sizes up to 60 inches in diameter. The Plastics Pipe Institute (PPI) funded a study to assess the performance of large diameter corrugated HDPE pipe beneath railroads under relatively shallow fills. Transportation Technology Center, Inc. (TTCI) conducted the test of 48-inch corrugated high-density polyethylene pipes at the Facility for Accelerated Service Testing (FAST). FAST operates as a test bed for railroad track and components, and for rail vehicles and components. The Federal Railroad Administration, the Association of American Railroads, and individual railroads and railroad suppliers (through in-kind contributions) have cooperatively funded the operations at FAST and its test programs. Typically, the train consist at FAST is four GP-40 locomotives and 80 315,000-pound gross rail load (GRL) cars. Approximately 120 million gross tons (MGT) of heavy axle load (HAL) traffic accumulate each year at FAST. Testing at FAST allows for safe, controlled testing of components without incurring the risk of in-service evaluations. The pipes were instrumented to allow data collection during train operations. Transducers were installed at various locations on the pipes to measure pipe wall strains and lateral, vertical, diagonal, and circumferential deflections. Strains and deflections were measured when the pipes were in place before the trenches were backfilled, after backfill, during normal operations at FAST after accumulating 1 MGT of HAL traffic, and after accumulating 96 MGT of HAL traffic. Also, the pipes were monitored visually and with a video camera. The pipes performed excellently, with negligible deflections, stresses, and strains resulting from the heavy railroad loading.