Slope Stabilization Using Recycled Plastic Pins

Abstract

Shallow slope failures are common in highway embankments in the north Texas region and pose significant maintenance problems for the Texas Department of Transportation (TxDOT). As a cost-effective alternative, recycled plastic pins (RPPs) can be utilized to stabilize slopes and prevent shallow slope failures. RPPs are fabricated from recycled plastic and waste materials (i.e., polymers, sawdust, and fly ash). It is a lightweight material and less susceptible to chemical and biological degradation than alternative reinforcing elements. RPPs are driven into the slope face, which provides additional resistance along the slip surface, increasing the factor of safety against shallow slope failure. The current study presents a field demonstration project of a highway slope reinforced with RPPs. The slope was located on the southbound side of U.S. Highway 287, near the St. Paul overpass in Midlothian, Texas. Surficial movement had taken place in the slope, resulting in cracks along the shoulder near the bridge abutment. Three 15.25-m (50-ft) sections over the cracked portion were reinforced using RPPs. In addition, two 15.25-m (50-ft) unreinforced control sections were provided between the reinforced sections to compare the performance. The northbound side of the slope was not reinforced and was also considered the control slope. After installation of the RPPs, the performance of the slope was monitored by using instrumented RPPs, inclinometers and a topographic survey. The performance monitoring results indicated that all of the reinforced sections were performing better than the control sections on the southbound slope. Two locations on the northbound control slope failed during the monitoring period. RPPs provided support and resisted failure of the southbound slope. Moreover, the RPP spacing at the crest played an important role in resisting the displacement.