Creep Characteristics of Composite Geomembrane Based on Viscoelastic Models

The creep characteristics of a composite geomembrane under different load levels were investigated by conducting a laboratory creep test for 2,100 h under 15 load levels from 10% to 80%. Test results showed that deformation increased rapidly when a load was applied, and the change in strain decreased gradually with an increase in time. The higher the load level, the higher the creep deformation and creep rate. When the load level was lower than or equal to 40%, the creep strain of the composite geomembrane increased linearly. When the load level was higher than or equal to 45%, the creep strain increase followed a quadratic function. When the load level was 40%–45%, the creep strain changed under the influence of the deformation characteristics of the composite material. Based on the creep test data, a piecewise empirical creep model with load level and time as parameters was established. The three-parameter and four-parameter viscoelastic constitutive models reflecting the creep properties were compared and analyzed, and it was found that the four-parameter model better reflected the creep characteristics of the composite geomembrane.