Modeling the Process of Thawing of Tailings Dam Base Soils by Technological Waters

At a Glance

Metadata	Details
Publication Date	2021-11-23
Journal	Applied Sciences
Authors	Nataliya Yurkevich, Irina Fadeeva, E. P. Shevko, Alexey M. Yannikov, S. B. Bortnikova
Institutions	Novosibirsk State University, V.S. Sobolev Institute of Geology and Mineralogy
Citations	2
Analysis	Full AI Review Included

Technical Documentation & Analysis: Permafrost Thawing Modeling

Executive Summary

This research provides critical insights into the geotechnical stability and environmental risks associated with diamond mine tailing dumps in permafrost regions, utilizing advanced thermophysical and thermodynamic modeling.

Core Problem: Quantifying the rate and extent of permafrost thawing and filtration channel formation caused by warm industrial water (2 °C to 15 °C) filtering through fractured dam base rock (limestone/marl).
Methodology: Coupled modeling approach combining Navier-Stokes/Brinkman equations (thermophysical heat transfer) and Gibbs free energy minimization (thermodynamic water-rock interaction).
Key Finding (Physical Heating): Warm water filtering through a 15 cm channel transfers substantial energy, calculated at 207.8 GJ to frozen rock and 8.39 GJ to thawed rock over a 10-year period.
Key Finding (Chemical Heating): Exothermic dissolution of limestone contributes an additional 0.37 GJ over 10 years, equivalent to 4.4% of the energy received by the thawed rock from physical heating.
Thawing Rate: Modeling predicts a permafrost thawing zone radius of 1.5 m radially from the filtration channel axis within the first year.
Geochemical Risk: Limestone dissolution and equilibration reactions promote the transition of hydrocarbonate anions into solution, indicating potential long-term structural degradation and leakage of mineralized drainage waters.

Technical Specifications

The following hard data points were extracted from the thermophysical and thermodynamic modeling parameters:

Parameter	Value	Unit	Context
Simulation Period	10	years	Total modeling duration
Frozen Rock Initial Temperature (T_i)	-4	°C	Well t3 (frozen zone)
Thawed Rock Initial Temperature (T_i)	+4	°C	Well t1 (thawed zone)
Circulating Water Temperature Range	2 to 15	°C	Annual variation entering channel
Filtration Channel Diameter	15	cm	Modeled sub-vertical crack
Water Inflow Velocity	100	m/day	Channel entrance speed
Total Heat Transferred (Frozen Rock)	207.8	GJ	Over 10 years (Physical Heating)
Total Heat Transferred (Thawed Rock)	8.39	GJ	Over 10 years (Thawed Rock Heating)
Energy from Chemical Dissolution	0.37	GJ	Over 10 years (4.4% of thawed rock heating)
Permafrost Thawing Zone Radius (Year 1)	1.5	m	Radial distance from channel axis
Limestone Thermal Conductivity ($\lambda$)	2.10	W/m/K	Well t1/2 (Thawed Limestone)
Technogenic Psephite Density ($\rho$)	1.77	g/cm³	Well t1/1 (Thawed Technogenic Deposits)
Medium Permeability ($k$)	10^-12	m²	Assumed constant for all units

Key Methodologies

The study employed a rigorous, multi-stage approach combining field sampling, laboratory analysis, and advanced numerical modeling:

Sample Collection: 47 rock cores (limestone, marl, technogenic deposits) and 20 surface water samples were collected from the settling pond and dam base for comprehensive analysis.
Geochemical Analysis: Rock samples were analyzed using X-ray fluorescence (XRF), X-ray diffraction (XRD), and vibrational infrared (IR) spectroscopy to determine petrogenic components, mineral composition (e.g., Pyrite, Magnetite, Calcite), and heavy/light fractions.
In Situ Water Quality Measurement: Field measurements determined pH (±0.03 units), redox potential (Eh, ±10 mV), and electrical conductivity (EC, ±1%) of the industrial water.
Thermophysical Modeling Setup: Heat transfer and rock thawing were calculated for a 10-year period. The filtration channel was modeled as a 15 cm diameter cylindrical channel, 66 m in length.
Fluid Dynamics Modeling: Water velocity distribution was calculated using the Navier-Stokes equations (free channel flow) and the Brinkman equation with a Forchheimer correction (porous medium flow).
Heat Conduction Modeling: The resulting velocity distribution was substituted into the heat conduction equation with a convective term to model temperature changes over time, using COMSOL Multiphysics software.
Thermodynamic Modeling: Physico-chemical modeling utilized PC Selector software to minimize the Gibbs free energy, calculating equilibrium compositions of solutions and minerals at 2 °C, simulating the water-rock interaction process in two reservoirs.
Reaction Quantification: The degree of limestone dissolution (estimated at 0.01% of the mass in bypass filtration zones) was determined indirectly by evaluating changes in bicarbonate ion concentrations between the settling and storage ponds.

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Applicable Materials

Research Requirement	6CCVD Material Recommendation	Rationale and Application
Geochemical Monitoring & Sensing	Heavy Boron-Doped Diamond (BDD) Plates	BDD electrodes offer superior electrochemical stability and a wide potential window, ideal for in situ monitoring of highly mineralized, acidic drainage solutions (pH, Eh, SO₄^2-, trace metals) in the tailing dump environment.
High-Performance Computing (HPC)	Optical Grade Single Crystal Diamond (SCD) Substrates	The complex thermophysical and thermodynamic modeling (COMSOL, Navier-Stokes) requires significant computational power. SCD provides the highest thermal conductivity (up to 2200 W/m/K) for efficient heat spreading and cooling of high-power CPUs/GPUs used in HPC clusters.
Durable Instrumentation Housing/Windows	Polycrystalline Diamond (PCD) Wafers	PCD offers extreme hardness and chemical inertness, providing robust, erosion-resistant substrates or protective windows for sensors and probes deployed directly into abrasive, chemically reactive rock and water filtration channels.

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View Original Abstract

The storage of wastes from mining and mineral processing plants in the tailing dumps in regions with cold climates has a number of environmental consequences. Interactions of water with tailings in cold climates often lead to the thawing of permafrost soils, formation of technogenic thawing zones, and leakage of drainage waters. In the case of fault zones development in these areas, technogenic solutions are often filtered outside the tailing dump, promoting further development of filtration channels. In order to prevent leakage of solution from tailing dumps over time, it is necessary to determine the thawing zones and prevent the formation of filtration channels. In the case of the formation of a filtration channel, it is necessary to know what rate of rock thawing occurred near the formed filtration channel. In this study, for the tailing dump of a diamond mining factory, we calculated two exothermic effects: (1) due to physical heating of dump rock by filtering industrial water with temperatures from 2 to 15 °C through the rock; and (2) due to the chemical interaction of industrial water with the dam base rock. The amount of energy transferred by the water to the frozen and thawed rock over 10 years was calculated using thermophysical modeling and was 207.8 GJ and 8.39 GJ respectively. The amount of energy that the rock received during the ten-year period due to dissolution of the limestones and equilibration of solutions was calculated using thermodynamic modeling and was 0.37 GJ, which is 4.4% of the average amount of energy, expended on heating the thawed rock (8.39 GJ).

Tech Support

Original Source

DOI: https://doi.org/10.3390/app112311089

References

2018 - Integrated environmental management of pyrrhotite tailings at Raglan Mine: Part 2 desulphurized tailings as cover material [Crossref]
2018 - How to avoid permafrost while depositing tailings in cold climate [Crossref]
2011 - Modelling temperature-dependent heat production over decades in High Arctic coal waste rock piles [Crossref]
2015 - Evolution of thermohydrodynamic fields at tailings dam at Kumtor mine (Kyrgyz Republic) [Crossref]
2019 - Performance of passive systems for mine drainage treatment at low temperature and high salinity: A review [Crossref]
2019 - Salinity and low temperature effects on the performance of column biochemical reactors for the treatment of acidic and neutral mine drainage
2019 - Environmental challenges and identification of the knowledge gaps associated with REE mine wastes management [Crossref]
2019 - Mining in the Arctic environment—A review from ecological, socioeconomic and legal perspectives [Crossref]
2018 - Review: Impacts of permafrost degradation on inorganic chemistry of surface fresh water [Crossref]
2019 - Influence of permafrost, rock and ice glaciers on chemistry of high-elevation ponds (NW Italian Alps) [Crossref]