LAUSR

Abstract Direct shear tests were carried out on sulfate-exposed and non-exposed shotcrete specimens to study the shear mechanical behaviors, taking into account the effects of normal stress and exposure time. The shotcrete mixtures with different water-to-binder ratio (w/b) were in-situ prepared using dry-spray method. Sulfate attack tests were performed by placing the shotcrete specimens in 5% w/w solutions of sulfate sodium subjected to natural dry-wet cycle condition. Results show that the mechanical behaviors of shotcrete specimens under direct shearing were significantly influenced by sulfate attack. For example, peak shear stresses of shotcrete specimens under the same normal stress condition decreased over exposure period, while peak shear stresses of specimens under different normal stress conditions were accorded with the Mohr-Coulomb (M-C) criterion. The nominal cohesion and nominal internal friction angle calculated from linear M-C criterion showed a distinct degeneration over exposure time. Based on these experimental data and a statistical model, a shear model of shotcrete specimens considering the effects of normal stress and sulfate-exposure time was proposed. By a series of parameter learning and model validations, this sulfate-damage shear model was proved to have good performance on the prediction of shear mechanical behaviors of sulfate-exposed and non-exposed shotcrete specimens.