Experimental and modelling study on nonlinear time-dependent behaviour of thin spray-on liner

Thin spray-on liners (TSLs) are fast-setting multi component polymeric materials applied on rock or coal surface with a thickness of 2-5 mm that have fairly high tensile strength, adhesion, and elongation capabilities. Compared to conventional surface support elements, TSLs with polymer content exhibit different material responses over time. As a matter of fact, the creep behaviour of TSLs under a constant load has a significance for the evaluation of the long term performances of TSLs. This paper investigates the nonlinear creep behavior of a polymer based TSL for different curing times. Experimental studies were completed to show the nonlinear time dependent response of the liner under various constant load and curing time conditions. Dogbone shape test specimens were sustained under constant loads up to 2 months of testing time for different test sets. New equations were proposed for rupture time prediction (creep rupture envelopes) which may aid support design engineers to estimate the effective permanent support time and maximum allowable strain amount of the TSL. Test results were used to construct nonlinear viscoplastic models and viscoelastic models consisting of one independent spring and multi Kelvin-Voight elements. A good agreement was obtained between model predictions and experimental values. Generated constitutive models might aid to further numerical studies in TSL literature