Strain measurement and interpretation of stabilising force in geogrid reinforcement

摘要

The stabilising force provided by a layer of geogrid reinforcement embedded in the body of a sloped fill subjected to loading from a footing located near the crest was investigated through a laboratory model study and the results are reported in this paper. This study indicates that the geogrid reinforcement could be instrumented more reliably with strain gauges installed in pairs, i.e., on top and bottom faces of the geogrid, at each location across the geogrid reinforcement and the use of the average strain minimises the influence of flexural strains in the geogrid. If only one strain gauge per location is used, the tensile strain and geogrid force estimated on the basis of nominal stiffness would not be accurate particularly at low load levels and considerable caution is required when using such an approach. The study demonstrates that the accuracy of the estimated stabilising force in the geogrid reinforcement could be enhanced by calibrating each pair of gauges as installed in position since each gauge installed at different locations across a geogrid sample would behave differently. Details of a relatively simple tensile testing method developed for calibrating these gauges and the use of calibration results for assessing the gradual development of stabilising force in the reinforcement in relation to the foundation load are discussed.