Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills

Mbonimpa, Mamert; Kwizera, Parrein; Belem, Tikou

doi:10.3390/min9030172

Cited by 8 publications

(3 citation statements)

References 24 publications

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“…In addition, the strength development of CPB is highly dependent on the evolution of its internal curing temperature. Indeed, the evolution of the CPB internal curing temperature on the mine site strongly depends on the placement temperature of the CPB in underground stopes (Cui & Fall 2016) and also on the heat exchange between the CPB mass and the rock wall (Beya et al 2019;Mbonimpa et al 2019). The CPB placement temperature is dependent on the variation of the CPB temperature during its flow in the pipeline distribution network and, consequently, on the heat exchange with the external environment and the internal heat generation due to viscous dissipation and fluid friction.…”

Section: Introductionmentioning

confidence: 99%

Backfilling in the permafrost: predicting pressure loss and temperature distribution along the paste backfill pipeline system

Kalonji¹,

Mbonimpa²,

Belem³

et al. 2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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Underground mine backfilling of permafrost open stopes with cemented paste backfill (CPB) has many challenges to overcome, including keeping the CPB unfrozen during pipeline transportation at low pumping costs and ensuring the required strength development under sub-zero temperature conditions. However, CPB strength development depends strongly on the evolution of its internal curing temperature that, in turn, is controlled by the CPB placement temperature (initial) in the stope and by the permafrost boundary temperature. Hence, it is relevant to predict the required pumping pressure and distribution of the CPB temperature along the pipeline by considering the internal and external heat exchanges and the thermo-rheological behaviour of the CPB. The objective of this paper is to simulate the CPB pipe flow in a full-scale pipeline distribution network anticipated for a mine located in the permafrost region of the north of Canada. For that purpose, CPB mixtures were prepared at 10°C (initial temperature expected in the backfill plant) in the laboratory with 5% of type HE Portland cement at a slump height of about 17.8 cm (corresponding to a solid concentration of about 76.3 %). The numerical simulations were performed using the non-isothermal pipe flow model of COMSOL Multiphysics ® 5.2 considering a distribution network of approximately 1,600 m long that includes an outdoor section of approximately 294 m exposed to air circulating at a speed of 1 m/s and to an extreme temperature of -50°C. The permafrost temperature was taken to be -5°C. and heated (at +2°C) underground openings were studied. A CPB flow velocity of 1.04 m/s and a pipe diameter of 0.1463 m were considered, as proposed by the owner of the mine project. Results indicate that the total pumping pressure is about 12 MPa (heated and unheated stopes) and the pressure gradient ( / ) distribution along the horizontal pipeline sections is about 13 kPa/m. A decrease in the CPB temperature was observed in the surface section, followed by an increase in the underground sections. This temperature increase can be explained by the predominance of heat transfer by convection rather than radial conduction of the heat generated by viscous dissipation. The effect of a thermal insulation of the pipeline section at the surface was also studied for comparison purposes.

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Section: Introductionmentioning

confidence: 99%

Backfilling in the permafrost: predicting pressure loss and temperature distribution along the paste backfill pipeline system

Kalonji¹,

Mbonimpa²,

Belem³

et al. 2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

View full text Add to dashboard Cite

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“…The lower the curing temperature is, the higher the ice content and strength of frozen CTB. Mamert [ 23 ] investigated the influence of 3% and 5% high-early-age cement on the strength of 80% slag and 20% ordinary cement-mixed CPB in a low-temperature curing environment. The study found that while high-early-age cement was beneficial to the development of CPB strength under low-temperature curing conditions, its hydration reaction was still inhibited by low temperature.…”

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of Strength and Deformation Behavior of Cemented Tailings Backfill under Curing Temperature Effect

Pan

Zhou

Wang³

et al. 2022

Materials

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Mineral resources are increasingly being developed in cold and permafrost regions. However, the mechanical and physical properties of cemented tailings backfill (CTB) cured at normal temperature are no longer applicable. To clarify the reasons for this variability, a series of tests were performed. The mechanical properties of CTB with different cement–tailings ratios (CTR, 1:4, 1:8, 1:12, 1:16, and 1:20) were tested at different curing ages (3, 7 and 28 days) and curing temperatures (20 °C, 5 °C, −5 °C, and −20 °C). The differences of CTB in mechanical and physical properties under positive- and negative-temperature curing conditions were analyzed, and the microscopic failure process of CTB under negative-temperature curing conditions was discussed. The results revealed that the mechanical properties and deformation behavior of CTB under positive- and negative-temperature curing conditions were different. The frozen CTB had higher early strength than the standard-temperature curing condition (20 °C), and the lower the temperature, the higher the early strength. The low-temperature curing condition, on the other hand, was not beneficial to CTB’s long-term strength. The low-temperature curing condition was not conducive to the long-term strength of CTB. After yielding, strain hardening and strain softening appeared in the deformation behavior of frozen backfill, indicating ductility. In contrast to the typical-temperature curing condition, the frozen CTB showed a new failure pattern that has little relation to curing time or CTR. Furthermore, the failure process of frozen backfill was reviewed and studied, which was separated into four stages, and altered as the curing time increased. The results of this study can act as a guide for filling mines in permafrost and cold climates.

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“…Although some researchers have studied the UCS and the cost of CPB, and achieved certain research results, few researchers have optimized the UCS and the cost of CPB at the same time [ 33 , 34 , 35 ], while it should be noted that the coal back-filling engineers tended to be cautious about the cost. Also, the use of intelligent combinatorial algorithms to predict the performance of CPB is missing in past research.…”

Section: Introductionmentioning

confidence: 99%

A Novel Design Concept of Cemented Paste Backfill (CPB) Materials: Biobjective Optimization Approach by Applying an Evolved Random Forest Model

He¹,

Cheng

et al. 2022

Materials

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For cemented paste backfill (CPB), uniaxial compressive strength (UCS) is the key to ensuring the safety of stope construction, and its cost is an important part of the mining cost. However, there are a lack of design methods based on UCS and cost optimization. To address such issues, this study proposes a biobjective optimization approach by applying a novel evolved random forest (RF) model. First, the evolved RF model, based on the beetle search algorithm (BAS), was constructed to predict the UCS of CPB. The consistency between the predicted value and the actual value is high, which proves that the hybrid machine learning model has a good effect on the prediction of the UCS of CPB. Then, considering the linear relationship between the costs and the components of CPB, a mathematical model of the cost is constructed. Finally, based on the weighted sum method, the biobjective optimization process of the UCS and cost of CPB is conducted; the Pareto front optimal solutions of UCS and the cost of CPB can be obtained by the sort of solution set. When the UCS or the cost of CPB is constant, the Pareto front optimal solutions can always have a lower cost or a higher UCS compared with the actual dataset, which proves that the biobjective optimization approach has a good effect.

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Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills

Cited by 8 publications

References 24 publications

Backfilling in the permafrost: predicting pressure loss and temperature distribution along the paste backfill pipeline system

Backfilling in the permafrost: predicting pressure loss and temperature distribution along the paste backfill pipeline system

Comparative Analysis of Strength and Deformation Behavior of Cemented Tailings Backfill under Curing Temperature Effect

A Novel Design Concept of Cemented Paste Backfill (CPB) Materials: Biobjective Optimization Approach by Applying an Evolved Random Forest Model

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