The Effect of Installation Damage on the Long-Term Design Strength of a Reinforcing Geosynthetic

Current practice in the design of reinforced soil is to calculate the long-term strength of a reinforcement damaged during installation by multiplying the two partial safety factors RF_ID and RF_CR. This procedure assumes that there is no synergy between them. To test this hypothesis, stepped isothermal method creep-rupture tests were performed on a polyester geosynthetic in its undamaged and damaged states. The geosynthetic chosen and the method of damage were specifically chosen to yield a 30% reduction in strength with the minimum of scatter. From simple tensile testing, the reduction factor for installation damage, RF_ID, was measured to be 1.42. Stepped isothermal method tests on the undamaged geosynthetic gave a creep-rupture characteristic with RF_CR = 1.70 for 106 hours (114 years). Thus, the predicted reduction factor for the long-term strength of the damaged geosynthetic is (RF_CR)(RF_ID) = 2.41. The measured reduction factor was 2.26, 7% less than predicted. It is recommended that the practice of using (RF_CR)(RF_ID) is upheld in the knowledge that the prediction will be slightly conservative.