Case History of Recycled Plastic Pins Supported Embankment on a Soft Clay Overlying Shale in Texas

Abstract

Load distribution in an embankment built over a soft foundation soil has always been a concern for engineers. Sharing the load with another load-bearing system will aid in improving the overall load distribution. The objective of this study is to monitor the mid-term performance of Recycled Plastic Pins (RPP) in load transfer behavior for an embankment. For this study, two field sections were constructed. One section was reinforced with RPPs having a cross-section of 15 cm × 15 cm and a length of 3 m, and the other section was left unreinforced, termed as the control section. For transmitting the load from the embankment to the RPPs, a load transfer platform (LTP) of geogrid and recycled crushed concrete aggregate (RCCA) was placed above the RPPs. The field sections were instrumented with inclinometers, piezometers, and pressure plates. The field data for the settlement, pore water pressure, and pressure variation on RPP and adjacent soil were collected and monitored for more than three years. A 2.4 m embankment height was applied which was constructed in three phases. The maximum settlement was found to be 35 mm in the reinforced section whereas in the control section it was significantly higher (73 mm). The dissipation of excess pore water pressure was found faster in the control section compared to the reinforced section resulting in more consolidation settlement in the control section. Based on the pressure plate data, RPPs carried about 14 times more load than the adjacent foundation soil in between RPPs. The higher value of load sharing implies that RPPs act as an effective system in distributing embankment load to the stronger soil strata. The use of recycled plastic pins over soft soil, thus, can be considered as a viable approach for ground improvement.