MEASURING STRAINS ON GEOGRID SPECIMENS UNDER THE LABORATORY TENSILE TEST

Geosynthetic products such as geogrids act a key role in geotechnical engineering as they are widely used in reinforcing pavement materials, embankments and retaining wall backfills. Therefore, measuring strains in geogrids is vital to evaluate their performances in geogrid-reinforced structures and, to determine their strength parameters such as secant stiffness and tensile strength. However, verifying the measured strain is required as these strains are affected by several factors including the gauge factor, data logging device, temperature and the quality of bonding between strain gauge and geogrid. Therefore, this research was conducted to verify the performance of strain gauges attached to geogrids and also to investigate the possibility of using Particle Image Velocimetry (PIV) technique and GeoPIV-RG software to measure the local strains developed in geogrid specimens under tensile testing in the laboratory. In this experimental study, a wide-width tensile test was conducted on composite geogrid test specimens while calculating/measuring its tensile strain by three methods, namely, using Geo-PIV-RG analysis, strain gauges attached to the specimens, and crosshead movements of Instron apparatus. Test results showed that there is a significant agreement between the strains obtained from strain gauges and GeoPIV-RG analysis for all the tests conducted. Therefore, it can be concluded that the PIV technique along with GeoPIV-RG program can be effectively used to measure the local strain of geogrids in the laboratory tests. In addition, properly installed strain gauges can be used in the field applications to measure strains in the geogrids.