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.

Stabilization of the Highway Slope using Recycled Plastic Pins

“…At the rest of the slope, the soil parameters were used from the existing soil test report. The details of the analysis are presented in Khan et al ( 1 , 8 ).…”

“…The RPP was considered as elastic material and modeled as a plate element, which worked as a lateral pile member in PLAXIS. The details of the study are also presented in Khan et al ( 1 , 8 ).…”

“…However, the conventional techniques for the repair of shallow slope failures are often deemed too expensive. Recycled plastic pins (RPPs) have been used in Texas, Missouri, and Iowa as a more cost-effective solution for slope stabilization than conventional techniques (5)(6)(7)(8). RPPs driven into the slope face provide an additional resistance along the slip plane that restricts the progression of the slip surface and increases the factor of safety.…”

Safety Prediction Model for Reinforced Highway Slope using a Machine Learning Method

“…These slope stabilization and repair techniques might work for a specific project; however, they are generally more cost and resource intensive when compared with a rather new and innovative method of shallow slope stabilization using recycled plastic pins (RPP) (7). Several shallow slope failures in Missouri, Iowa, and Texas have been successfully stabilized using RPP in recent years (8,9). Soil nails can be used for shallow slope failure repair.…”

“…However, the cost of RPP is much lower than the cost of soil nails. While typical slope stability methods, that is, ground anchor, soil nails and so forth, costs range from US$35 to US$80 per square foot, they are only US$5 per square foot when using RPP for stabilization ( 4 , 9 ). As such, it has been implemented more frequently in recent years.…”