Performance Evaluation of a Slope Reinforced with Recycled Plastic Pin

Abstract

The shallow slope failures are predominant in the North Texas area and pose significant maintenance problems for the Texas Department of Transportation (TxDOT). Typically, TxDOT maintenance team considers the traditional slope stabilization techniques, mainly concrete retaining wall. However, conventional remedial methods can be expensive in some instances and Recycled Plastic Pin (RPP) could be utilized to stabilize the shallow slope failure as a cost effective alternative. RPP are fabricated from recycled plastics and waste materials (i.e. polymars, sawdust, fly ash). It is a lightweight material and less susceptible to chemical and biological degradation compared to alternative reinforcing element. RPP are driven into the slope face that provides an additional resistance along the slip plane and increase the factor of safety. During the current study, a highway slope located over highway US 287 near the St. Paul overpass in Midlothian, Texas was stabilized using RPP. Surficial movement and cracks over the shoulder were observed near the bridge abutment due to rainfall. Two cracked section of US 287 slope were selected and reinforced using RPP in March 2011. The width of each reinforced section was 15.25 m (50 ft). Another 15.25 m (50 ft) section between two reinforced sections was used as a control section. To monitor the performance of the reinforced and control section, RPPs were instrumented with strain gauges and were installed in all sections. Based on the performance monitoring data of first year, the instrumented RPP at the unreinforced control section had larger strain due to rainfall compared to the reinforced section. In addition, no significant increment in strain was observed in the instrumented RPPs driven at the reinforced zone.