Time histories of tensile force in geogrid arranged in two full-scale high walls

Two tall geosynthetic-reinforced soil (GRS) walls, one 16.7 m high supporting a sloped embankment, and the other 21.1 m high with a level backfill, were constructed to support the taxi way of Mt. Fuji Shizuoka Airport, Shizuoka Prefecture, Japan, which was opened to service in June 2009. As only limited residual deformation during service is allowed and high stability is required, the backfill was a well-graded gravelly soil, which was well compacted at controlled water content and reinforced with geogrid reinforcement. In the respective walls, three representative geogrid layers were fitted with a number of electric-resistance strain gauges to monitor the geogrid tensile strains during and after construction to ensure high stability and sufficient serviceability. After the wall construction had been completed, the geogrid strains were either only increasing at a very low rate, or had stopped increasing, or had started decreasing. A series of in-air tensile loading tests were performed on different geogrid types used for the wall construction to evaluate their elasto-viscoplastic properties. The time histories of tensile force in the geogrid layers were estimated from the measured time histories of the geogrid strains based on a non-linear three-component rheology model using the model parameters determined by the in-air tensile loading tests. After the end of wall construction, the estimated geogrid tensile force was either increasing at a very low rate or was decreasing with time. Even at the locations where it tended to increase with time, the estimated geogrid tensile force never increased greatly by the end of a typical design life (i.e. 50 years) from the value at the end of wall construction. As the estimated maximum geogrid force at the end of the design lifetime is substantially lower than the respective design tensile rupture strengths, it is estimated that creep rupture failure of the geogrid is utterly unlikely. The analysis suggests that these estimates are also relevant when the lifetime is 100 years. The framework to estimate the time histories of reinforcement force from the time histories of measured reinforcement strains used in this study can be applied to other similar cases.