Polyester (PET) strap walls are gaining popularity in many countries. This technology first appeared in the late 1970’s. However, at present it is not described in national codes with the exception of the French AFNOR guidelines. This has led to PET strap walls being designed according to the Coherent Gravity Method, which  was developed for relatively inextensible steel reinforced soil walls, and in some cases using the Simplified Method and variants that were developed for relatively extensible polymeric (geotextiles and geogrids) walls. This paper summarizes recent studies by the authors that involved collecting data from instrumented PET strap walls from around the world with the objective to identify where PET strap walls fall between inextensible and extensible MSE wall behavior. The authors compared measured (observed) tensile reinforcement loads in these walls under operational conditions (working stress conditions) with predictions using the Coherent Gravity Method, Simplified Method and Simplified Stiffness Method. The first and second methods produced predictions that varied significantly from measured values but were conservatively safe. The Simplified Stiffness Method was shown to be much more accurate and without the excessive conservativeness observed in the other two methods. Included in the paper is a brief review of the accuracy of candidate pullout models for PET strap materials based on a database of pullout box tests and in-situ pullout tests compiled by the authors. The accuracy and utility of the different pullout models investigated are summarized and recommendations made. The combined work described in this paper provides design guidance for PET strap MSE walls so that they may be included in future editions of design codes and specifications used in different countries including the USA and Canada.

References

Miyata, Y., Bathurst, R.J. and Allen, T.M. 2019. Calibration of PET strap pullout models using a statistical approach. Geosynthetics International (online) (http://dx.doi.org/10.1680/jgein.19.00026).

Miyata, Y., Bathurst, R.J. and Allen, T.M. 2018. Evaluation of tensile load model accuracy for PET strap MSE walls. Geosynthetics International 25(6): 656-671 (http://dx.doi.org/10.1680/jgein.18.00032).