Rate-dependent tensile response of Polyvinyl Chloride geomembranes

One of the challenge that face the effectiveness of Polyvinyl Chloride geomembranes (PVC GMs) as a hydraulic barrier is the capacity to withstand unexpected mechanical actions, particularly tensile forces, during installation and throughout their lifespan. These forces pose risks of premature failure and impermeability degradation. In this study, the characterization of the short and long-term mechanical response of PVC GMs to uniaxial tensile forces has been investigated. Uniaxial tensile test have been performed for tensile rates spanning several orders of magnitude. Analysis of the true stress-strain curves reveals a significant decrease in tensile modulus, strength, and strain at failure at low strain rates, which are relatively close to those applied in situ. Long-term investigations have been conducted as well, through relaxation tests. Our key results unveil two distinct characteristic times in stress relaxation, with the fast relaxation occurring over the first 4 h. During this phase, the pre-relaxation loading rate affects the relaxation behavior. Beyond this phase, the relaxation behavior becomes independent from the pre-relaxation loading rate. Burger's rheological model is proposed to measure the stress relaxation at different rates. The model's results validate the existence of two characteristic times. • Higher tensile loading rates significantly increase the rigidity modulus of PVC geomembranes, while lower rates lead to reduced strength and strain at failure. • Laboratory tests at standard speeds may not accurately predict field performance, highlighting the need for testing at lower rates to avoid the risk of premature geomembrane failure. • Stress relaxation tests demonstrate two distinct relaxation stages, with initial rate-dependent behavior transitioning to a long-term rate-independent response after approximately 4 h.