A study has been performed to evaluate the field performance of existing high-density polyethylene (HDPE) pipe used for drainage applications on highway projects. Forty-five HDPE pipes were inspected at sites in South Carolina. The sites were statistically selected based on geographical location, pipe diameter, use, and age, and the condition of each pipe was not known before selection for inspection. Pipe performance was evaluated with respect to AASHTO and ASTM specifications, measurements of pipe deflection with a mandrel set to 5% deflection, and visual inspections using a video camera. The video camera inspections revealed circumferential cracks in 18% of the pipes, localized bulges in 20% of the pipes, and tears or punctures in 7% of the pipes. Deflections greater than 5% were observed in 20% of the pipes. Most of this observed damage was considered minor because the pipes were maintaining a relatively round shape with limited structural distress and still performing near to the original installation purpose. Installation problems such as poor preparation of bedding soils, inappropriate backfill material, and inadequate backfill cover contributed to the excessive deflection and observed internal cracking in pipes with observed damage. More pipes backfilled with Class IV soils did not pass the mandrel test than those backfilled with Class II or III soils. In addition, cracks were more apparent in Class IV backfilled pipes than they were in pipes backfilled with Class II or Class III soils. Forty-four percent of the pipes had less than the recommended height of soil cover. Appropriate installation procedures are essential to achieving high-quality performance.
Samenvatting