Fractional Order Viscoelastic Model for Stress Relaxation of Polyvinyl Chloride Geomembranes

Stress relaxation properties have a significant impact on the performance of polyvinyl chloride (PVC) geomembranes (GMBs) at the peripheral joints of the membrane faced rockfill dam (MFRD). This paper presents a fractional order viscoelastic model (FOVM) to measure the relaxation stress as a function of time. Model parameters were obtained by best fit to results from wide-width strip tensile tests conducted at three tensile rates and three initial strains for 48 h. The results of a 90 d stress relaxation test demonstrate the applicability of the model to describe the stress relaxation behavior of PVC GMBs. The tensile rate and initial strain marginally influenced the relaxation modulus rate, while having no effects on the fractional derivative order. Residual stress could account for the difference in relaxation stress between the longitudinal and transverse specimens. Finally, the FOVM could be used for predicting the service cycle under specifying failure stress criteria. Furthermore, it has great potential for applications in predicting the long-term deformation of PVC GMBs at the peripheral joints of MFRD. Furthermore, it has great potential for applications in predicting the long-term deformation of PVC GMBs at the peripheral joints of MFRD.