Generic creep behavior and creep modeling of an aged surface support liner under tension

Abstract

Polymer-based materials have been motivated to be an alternative support system element in the mining/tunneling industry due to their logistic and geotechnical benefits. Thin spray-on liner (TSL), a term to define the application of the material on the rock surface with a layer ranging from 2 mm to 10 mm in thickness, shows some promising results. TSLs are mainly composed of plastic, polymer, or cement-based ingredients to a certain proportion. This study intends to reveal the time-dependent response of TSL specimens, cured throughout 500 d, under four constant stress levels for stable laboratory conditions. The results were correlated using two interrelated equations to predict the material's service life (creep-rupture envelopes). The proposed correlations offered an insight into both the effective permanent support time and the strain amount at the liner failure. The time-dependent deformation of TSL, whose performance is highly responsive to creep behavior, was obtained so that the design engineers may use the findings to avoid the severe problems of material creep. Experimental data were also used to develop a Burgers (four-element) creep model. Since the liner has a nonlinear time-dependent behavior, creep models were built for each stress level separately. Subsequently, a generic equation was obtained using the nonlinear parametric dependencies. There is a good agreement between the proposed model and the experimental results. The proposed model can be used as a basis for future numerical studies related to the support behavior of aged surface support liners.

Keywords

• Time-dependent modeling
• Thin spray-on liner (TSL)
• Burgers model
• Creep constitutive model
• Stand-up time