Abstract
In order to consider the influence of mesoscopic characteristics of materials on the constitutive model of cemented paste backfill (CPB), the uniaxial compression variables and the damage constitutive model, considering the influence of porosity and pore size of filling materials, were derived based on the strain equivalence principle and Weibull probability distribution function. The nuclear magnetic resonance (NMR) tests and unconfined compression strength (UCS) tests were carried out on 8 groups of CPB specimens with different slurry concentrations and cement-tailings ratios. Then, the expression of damage strengthening coefficient is determined, and the stress-strain curves measured by the theoretical model were compared with the experimental ones. The results show that the uniaxial compression constitutive model proposed is in good agreement with UCS test results and can effectively describe the damage evolution law and the development process of stress-strain curve of CPB under uniaxial compression. The 28-day compressive strength of CPB can reach 8 MPa, the residual strength is about 1∼2 MPa, the elastic modulus is about 200∼2000 MPa, and the porosity is about 3∼5%. The CPB with slurry concentration of 74% and 76% and cement-tailings ratio of 1 : 4 and 1 : 6 is more reasonable, and the relevant mechanical parameters are more stable.
Highlights
In recent years, the global industrialization process is accelerating, the demand for mineral resources is increasing, the mining rate is increasing, and the tailings accumulation is increasing [1]. e storage of tailings wastes wastes land resources and causes increasingly serious environmental problems [2, 3]
Considering the influence of mesoscopic pore characteristics of Cemented paste backfill (CPB), a damage constitutive model based on damage strengthening coefficient is derived. en, the effectiveness of the model is verified by combining nuclear magnetic resonance (NMR) test and unconfined compression strength (UCS) test, and the damage evolution law of CPB under uniaxial compression is analyzed, which provides a basis for understanding the basic mechanical properties of CPB
5.1. eoretical Model Validation. e basic mechanical parameters such as elastic modulus, peak stress, and peak load strain can be obtained from the UCS test of CPB
Summary
The global industrialization process is accelerating, the demand for mineral resources is increasing, the mining rate is increasing, and the tailings accumulation is increasing [1]. e storage of tailings wastes wastes land resources and causes increasingly serious environmental problems (water pollution, air pollution, surface collapse, vegetation destruction, etc.) [2, 3]. Cemented paste backfill (CPB) is a kind of multiphase material formed by mixing a certain proportion of tailings and water with cement as the main cementation material and through mixing, vibrating, curing, and other processes It has the advantages of no pollution, low energy consumption, and good roof connection performance when used in underground mine filling [7, 8]. Wang et al [16] set up the damage evolution and constitutive model of CPB by using the damage mechanics theory and considering the delamination effect and studied the mechanical properties of different layered CPB. The cemented tailings backfill is a single homogeneous body formed by mixing cement, tailings, and water cementing Studies at this scale cannot reveal the relationship between the internal structure, composition, and mechanical properties of the backfill [22]. Considering the influence of mesoscopic pore characteristics of CPB, a damage constitutive model based on damage strengthening coefficient is derived. en, the effectiveness of the model is verified by combining nuclear magnetic resonance (NMR) test and unconfined compression strength (UCS) test, and the damage evolution law of CPB under uniaxial compression is analyzed, which provides a basis for understanding the basic mechanical properties of CPB
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