Compressive creep deformation and model of gangue backfill materials under the combined actions of seepage and stress
摘要
The overburden stress and water environment for seepage in mines significantly affect the load-bearing capacity and deformation of gangue backfill materials (GBMs). A self-developed stress–seepage test system for backfill materials was used to conduct creep compression tests on GBMs during loading. Test results show that GBMs with a large particle size are significantly deformed, rotated, and broken, while those with a minute particle size appear to argillize under the combined action of axial stress and seepage pressure. The compressive creep deformation of GBM samples includes instantaneous deformation, attenuated creep deformation, and steady creep deformation. As the axial stress and seepage pressure increase, the instantaneous strain and creep strain of GBMs both enlarge. For instance, at a seepage pressure of 3 MPa, the instantaneous and creep strains of GBMs at axial stress of 10, 15, and 20 MPa are 1.18, 1.26, and 1.30 times as large as those at axial stress of 5 MPa, and 1.20, 1.39, and 1.56 times as large as those at axial stress of 5 MPa, respectively. The instantaneous strain and creep strain constantly increase, while the strain increments both decrease under increasing axial stress and seepage pressure. The seepage pressure degrades the mechanical properties of GBMs, which exhibit significant viscoelastic effects and nonlinear characteristics. Based on the theory of fractional-order calculus, a damaged Abel dashpot is constructed to optimize the conventional Burgers model, thus establishing a fractional-order creep constitutive model of GBMs under seepage and stress action to describe the creep properties. The model parameters were identified and verified using the creep compression test results during step-wise loading under the combined actions of seepage and stress. The parameter identification accuracy, as measured by