Mechanical behavior, failure pattern and damage evolution of fiber-reinforced cemented sulfur tailings backfill under uniaxial loading

Abstract

In order to explore the mechanical properties of cemented sulfur tailings backfill (CSTB), uniaxial compression tests of cemented sulfur tailings backfill (CSTB) were carried out in the laboratory, and the effects of sulfur content and polypropylene fiber on the mechanical properties, failure pattern and damage evolution of the CSTB were systematically studied. Moreover, fiber factor γ is introduced to measure the impact of polypropylene fiber on mechanical behavior of CSTB. The peak stress, residual stress and elastic modulus of the CSTB all increase initially and decrease afterwards with the fiber factor γ increasing. When the fiber content is 0%∼0.6%, the three factors show exponential and quadratic function with the fiber factor γ increasing. The total strain energy, elastic strain energy and dissipative strain energy of CSTB at the peak stress point all increase first and then decrease with the fiber factor γ increasing, and all reach the maximum value when the fiber content is 0.6%. Under uniaxial loading, the elastic strain energy of CSTB presents a change characteristic of “gentle - rapid increase - slow increase - rapid decline” with the increasing axial strain, while the dissipative strain energy presents a change characteristic of “gentle - steady increase - rapid increase”. In addition, each strain energy (dissipative strain energy, total strain energy and total strain energy) of CSTB at the peak stress point all increase initially and decrease afterwards with the fiber factor γ increasing. Then, the piecewise damage constitutive model taking fiber factor γ into consideration was established. Under uniaxial loading, the damage evolution of backfill can be divided into four stages: no damage stage, slow growth stage, acceleration stage and damage failure stage. It shows that polypropylene fiber can effectively inhibit the damage and failure of CSTB, thus improving the bearing capacity and anti-deformation and failure ability of CSTB. The CSTB without fiber shows obvious shear failure characteristics, and there are obvious large-scale “Y-shaped” and “linear” failure cracks on the sample surface. There is not only one or two major large-scale cracks in the failure of CSTB containing fiber, but also the range of fracture surface is very limited, indicating that adding fiber can effectively inhibit the crack propagation of CSTB during failure and improve the overall anti-crack ability of CSTB.