Performance of Recycled Plastic Pin (RPP) for Slope Stabilization

Surficial failures of highway slopes in clayey soils are quite common throughout the United States. These failures commonly occur for the slope constructed with expansive clay, especially after prolonged rainfall. These failures are also predominant in North Texas area and cause significant maintenance problems for the Texas Department of Transportation (TxDOT). As an alternative to the conventional slope stabilization technique, a green and cost effective slope stabilization method using the Recycled Plastic Pin (RPP) had been utilized and tested for its performance. RPPs are driven into the slope face to provide additional resistance along the slip surface, which increases the factor of safety against shallow slope failure. Current study summarizes the long term performance of a highway slope on expansive clay reinforced with RPP. The slope is located over US 287 near the St. Paul overpass in Midlothian, Texas. Surficial movement had taken place over the slope, resulting in cracks over the shoulder and near the bridge abutment. Three 50 ft. slope sections were stabilized using RPPs in March 2011. In addition, two 50 ft. unreinforced control sections were utilized between the reinforced sections to evaluate the performance of slope sections stabilized with RPP. After installation of the RPPs, the performance of the slope was monitored by using instrumented RPPs, inclinometers and topographic survey. The performance monitoring results indicate that, maximum deformation of the reinforced slope section is less than 3.75 cm (1.5 in.). However, more than 38 cm (15 in.) of vertical settlement was observed at the control sections during the last 5 years monitoring period. Also, few slope-sections just opposite side of reinforced slope at the same highway failed during the monitoring period. Based on the last 5 years monitoring data, it was summarized that RPP can be successfully utilized for slope stabilization.