Abstract
At present, the filling mining method is widely used. To study strength evolution laws of cemented tailings backfill (CTB) under different curing ages, in the experiment, mine tailings were used as aggregates, ordinary Portland cement (PC32.5) was used as cementing materials, and different additives (lime and fly ash) were added to make filling samples with the solids mass concentration at 74% and the cement-sand ratios 1:4, 1:6 and 1:8. Based on the nuclear magnetic resonance (NMR) technology, the porosity test of filling samples with curing ages of 3 d, 7 d and 28 d was carried out, and the uniaxial compressive strength test was carried out on the servo universal material testing machine. The relationship between the uniaxial compressive strength and porosity of backfills and the curing age in the three groups was studied, and change laws of the porosity variation and strength growth rate of backfills were analyzed. Based on the variation in porosity, the strength evolution model of the CTB under different curing ages was established, and the model was fitted and verified with test data. Results show that the uniaxial compressive strength, porosity, porosity variation, and strength growth rate of the three groups of backfills gradually increase with the increase of the curing age, the porosity of backfill basically increases with the decrease of the cement–sand ratio, and the porosity of backfill decreases with the increase of the curing age. Porosity variations and relative strength values of the three groups of backfills under different cement-sand ratios obey an exponential function, and the two have a good correlation, indicating that the established filling strength evolution model can well reflect strength evolution laws of the CTB with the change of curing age.
Highlights
In the underground mining of metal mines, mining with filling has significant advantages in reducing tailings emissions and controlling surface subsidence [1,2,3], and with the society’s requirements for safe production and environmental protection in mines, filling mining methods are more and more widely used [4]
Zhang [10] and Ghirian et al [11] studied the relationship between the uniaxial compressive strength of cemented tailings backfill (CTB) and its curing age, and found that the strength of CTB increased with the increase of curing age, and increased with the increase of cement-sand ratio
A certain mine tailing was used as aggregate, ordinary Portland cement (PC32.5) was used as cementing material, and different additives were added to produce filling samples with mass concentration of 74% and cement-sand ratios of 1:4, 1:6, and 1:8, respectively
Summary
In the underground mining of metal mines, mining with filling has significant advantages in reducing tailings emissions and controlling surface subsidence [1,2,3], and with the society’s requirements for safe production and environmental protection in mines, filling mining methods are more and more widely used [4]. Due to the different strengths of the CTB under different curing ages, it will have a certain impact on the stability of the surrounding rock [7], thereby affecting entire underground mine production activities. Mechanical properties of CTB are one of the important indicators that must be considered [8,9], and an understanding of the strength evolution laws of CTB under different curing ages has important guiding significance for mine production practice. Li et al [12] has examined the effects of solid content (SC), cement/tailings (c/t) ratio, and curing time (CT) on rheological and mechanical properties of CTB mixes. Cheng et al [13] established the exponential function relationship between the uniaxial compressive strength of high concentration cementation filling and curing age by using the fitting approach. Qiu et al [17] established the damage constitutive model before the peak stress of the backfill based on the principle of strain equivalence
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