Temporary Lateral Support of a Concrete Retaining Wall Footing Using Recycled Plastic Pin

Abstract

Recycled Plastic Pins (RPP) are predominantly high density polyethylene materials that are fabricated from recycled plastics and other waste materials. It is a light weight material and less susceptible to chemical and biological degradation. The environmental resistant behavior of RPP makes it an attractive alternative compared to other degradable structural materials. Previous study indicates that RPP was successfully utilized for slope stabilization, arch bridges and piles. The current study presents the application of RPP as a temporary lateral support of a concrete retaining wall footing on a slope. The slope is located along highway Loop 12 near Union Pacific Rail Road (UP RR) over pass in Dallas, Texas. The concrete retaining wall is located at the middle of the slope that divided it into top and bottom slope. The crest of the top slope settled as much as 30 cm and footing of the retaining wall slid away from the top slope and resulted severe cracks near a construction joint. The site investigation program indicated that the sliding of the retaining wall occurred due to lack of lateral support. As a temporary remedial measure for 1-2 years, certain sections of the slope were reinforced using RPP. The spacing of RPP at the top and bottom slope was 0.9 m c/c and 1.2 m c/c, respectively. In addition, the first row of RPP at bottom slope was installed at the edge of the retaining wall footing and smaller spacing (0.6 m c/c) was provided near the critical cracked zone to provide additional resistance. After installation, topographic survey was conducted on monthly basis to monitor the lateral displacement of the stabilized slope. The field performance results indicated that the top of the retaining wall displaced as much as 15 to 20 cm after installation of RPP. On the other hand, 4 to 12 cm displacement was observed at the bottom of the wall which was less compared to the displacement at the top. RPP at the bottom slope provided resistance against the sliding and resulted less displacement at bottom slope.