Search Results (42)

The advent of digital mining has become a tangible reality in recent years. This digital evolution requires a predictive understanding of key elements, particularly considering the reliable communication infrastructures needed for autonomous machines. The LoRa technology and its underground propagation behavior can make an important contribution to this digitalization. Since LoRa operates with a high signal budget and long ranges in sub-GHz frequencies, its behavior is very promising for underground sensor networks. The aim of the development and series of measurements was to observe LoRa’s applicability and propagation behavior in active salt mines and to detect and identify effects arising from the special environment. The propagation of LoRa was measured via packet loss and signal strength in line-of-sight and non-line-of-sight configurations over entire mining sections. The aim was to analyze the performance of LoRa at the macroscopic level. LoRa operated at 868 MHz in the free band, and units were equipped with omni-directional antennas. The K+S Group’s active salt and potash mine Werra, Germany, was kindly opened as a distinctive experimental setting. The LoRa exhibited characteristics that were highly distinctive in this environment. The presence of the massive salt allowed the signal to bounce along drift edges with near-perfect reflection, which enabled travel over kilometers due to a waveguide-like effect. A packet loss of below $15\%$ showed that LoRa communication was possible over distances exceeding 1000 m with no line-of-sight in room-and-pillar structures. Measured differences of $\Delta 50\mathrm{dBm}$ values confirmed consistent path loss across different materials and tunnel geometries. This effect occurs due to the physical structure of the mining drifts, facilitating the containment and direction of signals, minimizing losses during propagation. Further modeling and measurements are of great interest, as they indicate that LoRa can achieve even better outcomes underground than in urban or indoor environments, as this waveguide effect has been consistently observed. Full article

Utilizing potassium salt aggregates and waste brine to produce underground cemented filling materials can address the waste storage issue. However, it is essential for the backfill materials to meet specific transport characteristics. This paper examines the transportation characteristics of lime-cemented mine backfill for a potash mine. The parameters were optimized for the cemented backfill process of potash mines through loop experiments and model simulations. Results indicate that the slump and fluidity of the backfill slurry diminished with increasing lime content and solid concentration. Additionally, the growth rate of pressure loss at the bent pipe and the pressure loss per unit distance in a horizontal pipe increased rapidly over transportation time, indicating a decline in the flowability of the backfill slurry. The lime dosage and solid concentration must align with the backfill requirements. When the lime dosage is 0.5%, the solid content is 70–75%; conversely, with a lime dosage of 0.7% and solid content of 65%, the maximum pumpable time extends to 1 h. The compressive strength of the cured backfill material after 28 days exceeds 1.01 MPa, meeting the transportation requirements for 300 m vertical pipes and 5000 m horizontal pipes. In the case study, the actual flow rate of backfill slurry surpasses the calculated critical flow rate. The estimated and measured values of on-site pressure loss per unit distance in a horizontal pipe exhibit a strong correlation. As the pressure loss per unit distance in a horizontal pipe rises, the discrepancy between the calculated and measured values also increases. When the solid content exceeds 65%, the loop test slightly enhances the compressive strength of the lime-cemented backfill. The findings from this article can aid in determining the on-site backfill process parameters with lime as a binder. Full article

This paper addresses the numerical simulation of unsteady, non-isothermal ventilation in a dead-end mine working of a potash mine excavated using a borer miner. During its operations, airflow can become unsteady due to the variable operating modes of the borer miner, the switching on and off of its motor cooling fans, and the movement of a shuttle car transporting ore. While steady ventilation in a dead-end working with a borer miner has been previously studied, the specific features of air microclimate parameter distribution in more complex and realistic unsteady scenarios remain unexplored. Our experimental studies reveal that over time, air velocity and, particularly, air temperature experience significant fluctuations. In this study, we develop and parameterize a mathematical model and perform a series of numerical simulations of unsteady heat and mass transfer in a dead-end working. These simulations account for the switching on and off of the borer miner’s fans and the movement of the shuttle car. The numerical model is calibrated using data from our experiments conducted in a potash mine. The analysis of the first factor is carried out by examining two extreme scenarios under steady-state ventilation conditions, while the second factor is analyzed within a fully unsteady framework using a dynamic mesh approach in the ANSYS Fluent 2021 R2. The numerical results demonstrate that the borer miner’s operating mode notably impacts the velocity and temperature fields, with a twofold decrease in maximum velocity near the cabin after the shuttle car departed and a temperature difference of about 1–1.5 °C between extreme scenarios in the case of forcing ventilation. The unsteady simulations using the dynamic mesh approach revealed that temperature variations were primarily caused by the borer miner’s cooling system, while the moving shuttle car generated short-term aerodynamic oscillations. Full article

Known as the “Ear of the Earth”, Lop Nor has become one of China’s four largest uninhabited areas due to environmental changes. Lop Nor is rich in mineral resources, including potassium salt, which has good quality and has been largely mined since 2002. This study focuses on the surrounding area of the Lop Nor Potash Salt Field, which covers an area of 80,036.39 square kilometers, spanning from 39.29° N to 41.84° N and 88.92° E to 92.26° E. The research is based on 1 km resolution precipitation, potential evapotranspiration, temperature data, and 250 m resolution NDVI data spanning 2002–2022. This study is devoted to exploring the trend of precipitation changes in the region surrounding the Lop Nor salt field since the start of the construction of the salt field, exploring the climatic impacts of the construction of the salt field on the surrounding region, and analyzing the correlations related to the changes in precipitation by selected meteorological factors. The Sen and Trend-Free Pre-Whitening Mann–Kendall trend analysis method was used to analyze the trend of precipitation data over the years. Combining with the data of the salt field location, the influence of the development of the salt field on regional precipitation was analyzed both temporally and spatially. The bias correlation analysis method was used to explore the correlation between maximum temperature, potential evapotranspiration, Normalized Difference Vegetation Index, and precipitation. The results of this analysis indicate that between 2002 and 2022, the study area exhibited both increasing and decreasing trends in precipitation. The region experiencing decreasing precipitation is predominantly located in the southwestern part of the study area, encompassing approximately 62% of the total area. Conversely, the area showing increasing precipitation is situated in the northeastern part, accounting for 38% of the total area. Field visits and survey data further corroborated the observed trend of increased precipitation in the northeastern region. Based on these findings, it is hypothesized that the development of salt flats has contributed to the increased precipitation, thereby alleviating regional drought conditions. Additionally, a partial correlation analysis of meteorological factors and precipitation revealed significant correlation. Temperature, potential evapotranspiration (PET), and the Normalized Difference Vegetation Index (NDVI) all exhibited varying degrees of correlation with precipitation. Temperature and potential evapotranspiration were the primary meteorological factors showing significant individual correlations. This study discusses the impact of salt field development and other climatic factors on the drought situation in Lop Nor and quantitatively analyzes the trend of precipitation changes in the study area and the factors affecting it. Water resources are scarce in China’s desert areas, and this research can provide a scientific basis for the state to formulate long-term plans for ecological protection and desert management, and it can also provide guidance for industrial development in desert areas. At the same time, it can provide important data and cases for global climate change research, offering experience and technical support for international cooperation in desertification control. Full article

In today’s world, advanced technologies are indispensable. In the field of mining, the use of machine-learning techniques is a reliable and productive way to solve various problems. This article touches upon the issues of increasing the recovery rate at potash mines, using the technology of backfilling with hardening materials. The compositions of backfills with increased strength are developed. The results of laboratory studies are given. To reduce the labor intensity of the experimental work, as well as to develop and validate methodological approaches to machine-learning introduction in the fields of mining and geomechanical research, this paper also presents the results of the predicted calculated values of the multi-component backfill strength, obtained with the help of neural networks. Full article

Airborne dust is an important contaminant affecting the health and the environment, and a crucial concern in many workplaces such as animal facilities and potash mines. One of the techniques used for dust control is electrostatic particle ionization (EPI). This technology has been proven effective in reducing airborne dust; however, it has downsides, such as the generation of ozone and corrosion of electrodes. Thus, this study tested a corrosion-resistant carbon-fiber discharge electrode and compared it with electrodes commonly used in EPI systems, that is, stainless-steel and tungsten electrodes, in terms of collection efficiency for potash dust and wheat flour (representative of livestock dust), ozone production, and power consumption. The carbon-fiber electrode performed comparably to stainless-steel electrodes, particularly for potash dust, and performed better than the tungsten electrode in terms of dust collection efficiency. Moreover, it had the lowest energy consumption and generated the least amount of ozone. However, because of the limitations of this study (e.g., fewer samples, low air velocity, controlled conditions, and the use of wheat flour instead of livestock dust), tests under real barn or mining conditions are necessary to confirm the results. Full article

This study evaluated the properties and processing of cemented paste backfills (CPBs) for potash mining through loop tests. The CPBs were made with steel slags as the binder, granulated potash tailings as the aggregate, and waste brine water as the liquid phase. The effects of solid concentration and steel slag dosage on the transport and mechanical properties of CPBs were assessed. The loop test demonstrated that all CPB slurries performed well, exhibiting strong long-distance pipeline transport capabilities. The 28-day compressive strength of the backfills exceeded 1 MPa, meeting the design requirements for backfill strength. The key rheological parameters, including yield stress (τ₀) and viscosity coefficient (η), were comprehensively and theoretically analyzed based on the variations in pressure loss per unit distance of the filling slurry measured during the loop test. The empirical formulas for CPB pressure loss, accounting for varying flow rates and pipeline diameters, were derived with an error margin under 2%. The response surface analysis showed that the affecting extents of factors on pressure loss in CPB slurry were ranked as follows: solid concentration > cementing agent content > flow rate. This study offered valuable guidance for the processing of potash mine backfill operations. Full article

This paper investigates the flow performance and mechanical properties of underground gelled filling materials made from potash mine tailings, using lime as a gel. It demonstrates the feasibility of using lime as a gel, potash mine tailings as aggregate, and replacing water with potash mine tailings to create filling materials that meet design requirements for flow and compressive strength. The role of lime in the hardening process is explored through X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectroscopy, thermogravimetric analysis, and infrared analysis. Results show that hydration products vary with lime dosage. With 9% lime (L9), the products are primarily ghiaraite (CaCl₂·4H₂O) and carnallite (KMgCl₃·6H₂O); with 5% lime (L5), tachyhydrite (CaMg₂Cl₆·12H₂O) predominates, along with minor amounts of antarcticite (CaCl₂·6H₂O) and korshunovskite (Mg₂Cl(OH)₃·4H₂O); and with 2.6% lime (L2.6), the products include tachyhydrite, ghiaraite, bischofite (MgCl₂·6H₂O), and korshunovskite. These hydration products form a dense, interwoven structure, enhancing the strength of the filling material. This study offers a theoretical foundation for using lime gel as a filling material in potash mining, with significant implications for sustainable mining practices. Full article

The sand–gravel brine deposit in the Mahai Basin is a newly discovered large-scale potassium–bearing brine deposit. The potassium–bearing brine is primarily found at depths exceeding 150 m within the porous alluvial and fluvial sand–gravel reservoir of the Middle to Lower Pleistocene. This deposit is characterized by a relatively shallow water table, moderate–to–strong aquifer productivity, high salinity, and a KCl content that meets the conditions for exploitation, with the advantage of reduced salt crystallization during well mining, making it a potential reserve base for potash development. A geochemical analysis of the sand–gravel brine revealed consistent trends for the major ions K⁺, Na⁺, Mg²⁺, Cl⁻, and SO₄²⁻ along the east–west axis of the alluvial fan, while Ca²⁺ showed an opposite trend compared to Mg²⁺. Along the exploration lines from north to south, the concentrations of the main ions gradually increase. The brine is enriched in Na⁺ and Cl⁻ ions, while SO₄²⁻ and HCO₃⁻ are depleted. In the K⁺-Na⁺-Mg²⁺/Cl⁻-H₂O (25 °C) quaternary phase diagram, the brine falls within the halite stability field, with the hydrochemical type classified as chloride type. The brine coefficient characteristics indicate a multi-source origin involving residual evaporation, salt rock leaching, and metamorphic sedimentary brine. Comparison studies of the ionic composition and isotopic signatures (δD, δ¹⁸O, δ³⁷Cl, and δ⁷Li) of deep sand–gravel brines in the study area with interstitial and confined brines in the southern depression suggest similar geochemical characteristics between them. The genetic analysis of the deposit proposes that during the basin tectonic evolution, the potassium-rich interstitial and confined brines originally located in the southern depression of the Mahai Basin were displaced under compressional forces and migrated northward as the depositional center shifted, eventually backfilling into the loose alluvial and fluvial sand and gravel reservoirs at the front of the Saishiteng Mountains, forming the deep sand–gravel brine deposits in the foreland. Full article

The thermal regime of underground mines, shaped by air temperature, velocity, and relative humidity, is a crucial factor for production and the health and safety of miners. While many aspects of this thermal regime have been thoroughly studied in the literature, local heat sources from mechanized equipment, such as load–haul–dump machines, conveyors, and auxiliary fans, have received comparatively little attention despite their significant impact on the thermal environment in mining development areas and stopes. This paper presents findings from a comprehensive study of the microclimatic air parameters in several nickel–copper and potash mines. We focus specifically on variations in air temperature in areas where mining equipment is operational. The heat output from different types of equipment, including load–haul–dump units, cutter–loaders, drilling rigs, conveyors, and auxiliary fans, has been quantified. We established empirical relationships for heat emissions from these machines and conducted a comparative analysis of their heat outputs. The main advantage of these relationships is their simplicity and the minimal number of input parameters required, making them practical for use in the field. Full article

The article describes the peculiarities of strength and stability evaluation for deep geotechnical structures located in salt rock masses at great depths. A number of numerical studies are presented for the deep mining excavations of various cross-sections. The numerical simulations are conducted using a specific coupled algorithm of the finite element method (FEM) and distinct element method (DEM), which allows not only the prediction of dangerous zones in the undermined rock mass but also to simulation of the block fracture of the rock mass directly. Potential critical zones in the rock mass are established using an original complex limit state criterion for rock masses and FEM simulation results. Mentioned original criterion is a specific multicriterial method, which considers potential tensile, compressive and shear failure as well as crack propagation. To define the block-structure formulation in the rock mass it is proposed to use the Lade criterion in the complex limit state zones. Furthermore, block-structured rock mass behavior is simulated using DEM to predict its block-like fracture. The results of numerical studies clearly show that the mechanical behavior of potash salt rock masses significantly differ at moderate and great mining depths. Namely, the volume of the limit state zones nonlinearly increases with the increase in the mining depths up to double the size of the excavation cross-section. However, the exact amount of potentially failed rock mass has to be established using the direct DEM simulation in the limit state zones. Full article

The planned closure of potash mines achieved through the injection of highly mineralized brines into the worked-out area is a complex process. A critical concern arises when brines obstruct the aerodynamic connections between the flooded mine’s airspace and the atmosphere, potentially leading to the formation of closed cavities where explosive gases can accumulate. To address this hazard, it is imperative to develop systems capable of extracting the gas–air mixture from the unflooded part of the worked-out area. Two distinct scenarios are examined: the first involves controlled flooding with saturated brines, while the second contemplates flooding resulting from a hypothetical breakthrough of supra-salt strata, leading to the ingress of groundwater into the worked-out area. A novel mathematical model is introduced to predict the evolution of gas–air mixture parameters in the unflooded part of the worked-out area. Utilizing this model, we assess the effectiveness of proposed measures designed to eliminate explosive gases from the worked-out area. Specifically, a pipeline system is proposed for the removal of gases. The findings from this study contribute valuable insights into ensuring the safe and efficient closure of potash mines, shedding light on potential risks and effective mitigation strategies for gas-related hazards during planned flooding. Full article

The hydrogeochemical research of groundwater in the Bieletan area, China’s largest potash producing zone, used a variety of methods, including multivariate analysis, saturation index, and hydrogeochemical modeling. Water samples were collected and analyzed for physicochemical parameters, along with soluble ions from soil cores. The results showed that total dissolved solids (TDS) of groundwater exceeded 300 g/L, with the main hydrochemical characteristics being Cl-Mg type and Cl-Na type. Groundwater is recharged by lake water and canal water, with evaporation being the main factor affecting water chemistry. Hydrogeochemical modeling analyzed the processes occurring from these two different recharge sources: mineral precipitation mainly occurred with lake water recharge, while mineral dissolution mainly occurred with canal water recharge. Regarding potash dissolution, canal water and lake water recharge resulted in 8.860 mmol/L of polyhalite dissolution and 0.278 mmol/L of carnallite dissolution, respectively. This study highlights the complex hydrogeochemical processes controlling groundwater in the potash-rich Bieletan area, providing insights for water resource management and potash mining. Full article

Humanity development is associated with higher spiritual and social behaviour and financial shape, which is an undeniable factor of urbanisation. Previously, in areas of georesource concentration, cities and settlements were formed with people exploiting these georesources. However, imperfect technologies lead to rapid depletion of reserves and industrial and environmental disasters, which affect the vulnerability of cities and the people living in them. The analysis of applied technologies has demonstrated that potash extraction is accompanied by a low recovery ratio, high mine accidents, and environmental problems. The principles of sustainable development of geo-resources for the creation of mining technologies that ensure industrial safety, environmental sustainability, and extending the life of the mining enterprise to save working places will reduce the vulnerability of cities. This article proposes the use of the room-and-pillar mining method with the replacement of natural supports with artificial ones. Three-stage stoping with backfill is considered. Numerical modelling has shown stabilisation of mining and geomechanical processes, which confirms the prospectivity of the method with backfill. For these purposes, this research presents a new backfill composition based on local industrial waste. Schemes of backfill preparation and feeding into the mined-out space are proposed. The proposed technology, based on the principles of sustainable development of georesources, is the foundation for an economically profitable, environmentally friendly, and socially responsible mining enterprise. The implementation of the principles of sustainable development of georesources will allow for the preservation of cities and reduce their vulnerability. Full article

There are considerable reserves of low-grade solid potash resources in the shallow part of Mahai Salt Lake in the Qaidam Basin, and the lithium brine resources resulting from solid–liquid conversion and mining are quite abundant. The comprehensive utilization of these resources is an important and urgent problem. In this study, to fully utilize these resources, the shallow low-grade solid potash ore in Mahai Salt Lake was used for systematic simulated ore dissolution experiments, combined with geochemical and X-ray diffraction analyses. The following key results were obtained: (1) Most Li⁺ in the Mahai mining area was deposited on the soluble salt minerals in silt or clay, and the appropriate concentration of solvent can help to dissolve more Li⁺ and K⁺; (2) the saturation time of Li⁺ was longer than that of K⁺. Therefore, the dissolution time for the mine can be appropriately extended during the production process to dissolve more Li⁺; (3) the solid–liquid conversion aqueous solution mining method can separate the lithium part of clay deposits and is associated with salt rock in the brine, which is a potential lithium resource. These experimental results provide a theoretical basis for salt pan production. Full article