Standard Guide for Use and Application of Geosynthetic Reinforcement Reduction Factor Test Results

Abstract

4.1 The long-term material strength of geosynthetic reinforcement material is a critical design parameter for many civil engineering projects including, but not limited to, reinforced wall structures and reinforced slopes. Geosynthetic reinforcement products are produced using a variety of polymeric materials and using a variety of manufacturing procedures. Accordingly, product-specific testing using representative produced products is recommended for establishment of long-term material strength for products used as reinforcement in structures. 4.2 The primary use of the test results obtained from a reinforcement testing program is to determine the available long-term (that is, end of design life, typically 75 years) material strength, Tal, of the reinforcement. The available long-term strength, Tal, is calculated as follows: 4.3 This long-term geosynthetic reinforcement strength concept is illustrated in Fig. 1. As shown in the figure, some strength losses occur immediately upon installation, and others occur throughout the design life of the reinforcement. Much of the long-term strength loss does not begin to occur until near the end of the reinforcement design life. 4.4 The value selected for Tult, for design purposes, is the minimum average roll value (MARV) for the product. This minimum average roll value, denoted as TMARV, accounts for statistical variance in the material strength. Other sources of uncertainty and variability in the long-term strength result from installation damage, creep extrapolation, and the chemical degradation process. It is assumed that the observed variability in the creep rupture envelope is 100 % correlated with the short-term tensile strength, as the creep strength is typically directly proportional to the short-term tensile strength within a product line. Therefore, the MARV of Tult adequately takes into account variability in the creep strength. 4.5 In accordance with AASHTO R 69-15, the test program results provided in geosynthetic reinforcement design reduction factor test reports are focused on characterization of the product line, specifically testing representative products within the product line to accomplish that characterization. 4.6 The guidelines provided in this document explain how to use the test data to characterize the entire product line with regard to long-term strength and durability properties.