FIELD OBSERVATIONS ON THE LOAD-STRAIN-TIME BEHAVIOR OF GEOGRID REINFORCEMENT

Field data are reported that describe the load-strain-time relationshi p of geogrid reinforcement in a reinforced soil structure. The data ar e for a period exceeding 5 years and reveal a continued strain in the reinforcement, which occurs at nearly constant load. The response to l oading is attributed to creep of the polymeric material. A comparison of the field data with laboratory isochronous load-strain curves, from rapid loading creep tests performed at a temperature similar to the m ean annual temperature in the backfill soil, shows the curves describe very well the magnitude of creep strains observed in the field. Impli cations of the load-strain-time performance data are assessed with ref erence to the use in design of a tensile strength established from the rapid-loading creep test and wide-width strip test. The need to clari fy, in design of polymeric reinforced soil structures, between a safe and allowable tensile strength is emphasized.