Practice and Research of Geosynthetic Reinforced Soil Walls in Australia - Reinforced Soil Engineering: Advances in Research and Practice - page 251

R57 has sometimes been criticized as an excessively detailed document.
However, it can also be argued that until an enforceable and truly performance-
based specification is developed, a detailed design specification is needed to
avoid “contractual misinterpretation.”
The more debatable aspect of R57 is the methodology used to assess the
design strength of the reinforcement (at the end of the design life of the GRS
wall). Following the philosophy of BS 8006 (1995), the relevant equations for
design against reinforcement rupture are

T * # T dr ð 1 Þ

T B
f m

T dr ¼ ð 1a Þ

where T* is the factored reinforcement tension (which are generally calculated
with partial load factors of 1.25 on dead load and 1.50 on live load), T dr is the
design strength for reinforcement rupture, T B is the base strength of the material at
the prescribed design life, and f m is the partial factor for reinforcement strength. T B
is derived by extrapolation of sustained load test data presented by the specialist
GRS wall contractor (or geosynthetic manufacturer) as illustrated in Fig. 2.
A test duration of at least 1 year is required. Based on available data, the
ratio T dr /T uo , where T uo is the tensile strength as measured in a quick tensile test,

Figure 2 Long-term strength of geosynthetic reinforcement by stress rupture method.