Sensor-Enabled Geogrids for Performance Monitoring of Reinforced Soil Structures

Sensor-enabled geogrid (SEGG) technology has been introduced by the authors in the past few years as a new category of geogrid products that possess embedded strain-sensing capability in addition to their conventional reinforcement/stabilization function in geotechnical and transportation applications. In this technology, the strain-sensing function of modified geogrids (SEGG products) arises from their tensoresistivity, which is the sensitivity of the polymer composite electrical conductivity to tensile strain. An SEGG product is filled with a target concentration of conductive fillers such as carbon blacks and carbon nanotubes. The authors' previous studies on SEGG to date were focused on the in-isolation performance of the unitized SEGG and the coating of yarn-type SEGG samples. In the continuation of a long-term study, this paper reported the latest findings on both the in-isolation and in-soil tensoresistivity performance of polyethylene terephthalate (polyester) yarn SEGG specimens that were coated with a strain-sensitive carbon black-filled PVC composite. The formulation of the coating composite was presented and the influences of the soil confining pressure and loading (i.e., strain) rate on the tensoresistivity and tensile strength of SEGG specimens were investigated. It was found that greater confining pressures and strain rates both result in a reduction in the tensoresistivity of the SEGG samples. However, both the magnitude and reproducibility of the measured tensoresistivity in the in-soil tests carried out in this study were judged to be acceptable for civil engineering applications, given that the accuracy of strain distributions in geogrids can be improved by increasing the number of strain data points in each reinforcement layer at a significantly lower cost compared to the conventional methods. It was thus concluded that the SEGG technology holds promise to serve as an alternative to conventional instruments for the performance monitoring of geotechnical structures.