Volume 25, Issue 6 (November 1997)
Local Versus Global Strain Measurement of a Polymeric Geogrid
Polymeric geogrids, which consist of a planar polymeric material with a grid-like configuration, have become increasingly popular as a reinforcement inclusion in soil structures. As the use of geogrid materials has increased, so has the need to quantify both the in-air and in-soil mechanical behavior. Bonded resistance strain gages have been used to quantify the strain response of geogrids. Problems associated with gage mounting, bonding, and environmental protection must be addressed. The relationship between the local measured strain and the global strain must be established. In this paper, these issues have been addressed by conducting in-air tension tests on a particular geogrid. In general, it has been found that strain gages can be successfully bonded to the ribs of geogrids such that strains up to 7% can be recorded. These gages were successfully protected and used in a field application for a period of five months. Strains measured along the ribs of the geogrids were seen in this study to be 1.25 to 1.6 times the average strain applied across the specimen for monotonic loading. The two strains correspond nearly one-for-one for cyclic loading. The presence of the strain gage and accompanying cement appears to have little effect on the strain response.