Evaluation of tensile load model accuracy for PET strap MSE walls

Abstract

There are conflicting opinions regarding whether or not mechanically stabilized earth (MSE) walls constructed with polyester (PET) straps should be classified as relatively inextensible type, and thus fall into the same category as steel reinforced soil walls, or whether they should be viewed as relatively extensible and grouped with MSE walls that are designed with geosynthetic sheet reinforcement such as geogrids and geotextiles. The differences in predicted loads using models associated with each category can be significant. The writers collected 71 measurements from eight different instrumented PET strap wall projects. The data showed that these PET strap walls behaved more like extensible geosynthetic walls constructed with geogrids and geotextiles (or at least at the stiffer end of these walls) rather than MSE walls with relatively inextensible (steel) reinforcement. The accuracy of the Coherent Gravity Method, the Simplified Method and the Simplified Stiffness Method was assessed statistically using analysis of bias values, where bias is the ratio of measured to predicted load. The Coherent Gravity Method and the Simplified Method resulted in conservative (safe) estimates of reinforcement loads under operational conditions on average. However, the Simplified Stiffness Method was the most accurate and did not result in an excessive level of conservativeness.