High-altitude Mine Research Articles

Обеспечение безопасности труда горнорабочих совершенствованием электрических сетей при подземной добыче руд

In recent years, more attention has been paid to the increase in energy consumption by mining enterprises operating mines due to the need to replace the installed electric equipment and implement automated process management systems in mining and transport areas of the mine, which ultimately ensures safe and faultless operation of power supply system at various voltage levels in both individual subdivisions and the entire mine. During the experimental studies and solving problems, safe conditions for maintaining electric installations of the mine and maintenance personnel will be ensured. Weaknesses of the grid insulation and its elements have been detected; stable values for the resistance of motor insulation, switching equipment, laid cables, and the relevant probability distribution densities have been provided. This enables the replacement of individual unstable sectors of the power grid with new cables and equipment, which will significantly improve the safety of mining operations in the conditions of a high-altitude mine. It has been established that the motors used as actuators for scraper winches and fans must be replaced with motors of similar power equipped with organosilicon insulation or filling of frontal parts with enamel paint. The conducted studies enable the development of a comprehensive inspection methodology of the mine power supply system’s insulation elements and its application for further studies at other mines.

Bronchial asthma and work in high-altitude mines

In occupational health, the management of patients with preliminary and periodic medical examinations for work in harmful conditions, for example, in high-altitude conditions, can be a difficult task. Bronchial asthma is one of the unequivocal contraindications to work in the highlands, however, in light of recent successes in achieving asthma control and the introduction of new types of therapy, this issue may require additional discussion. The article presents arguments both in favor of admitting patients with bronchial asthma to the highlands and against such a decision. The first group includes the elimination of allergens, long-term successes in the treatment of bronchial asthma in the highlands, as well as the fact that the decision not to allow it was popular in the era before the introduction of effective basic therapy for bronchial asthma with inhaled corticosteroids. The group of arguments "against" includes cold air, possible compensation only at relatively low altitudes, as well as remoteness, the inability to fully control compliance with patient requirements and the presence of typical industrial hazards in the form of allergens and irritants in production. It is particularly possible to emphasize the weakness of the evidence base, the extremely scarce number of published studies and the need for careful planning and conducting high-quality prospective observations of high-altitude mine workers, which can serve as a basis for the formation of an evidence base for adjusting admission conditions in the future.
 Ethics. The study did not require permission.

Impact of Ecological Restoration on the Physicochemical Properties and Bacterial Communities in Alpine Mining Area Soils.

Ecological restoration has notably impacted microbe and soil characteristics in abandoned open pit mines, especially in alpine regions. Yet, the adaptive responses of microbial communities in the initial years of mine site restoration remain largely unexplored. This study endeavors to offer a thorough comprehension of soil properties and microbial dynamics during the initial phases of alpine mining land reclamation. It places emphasis on physicochemical properties and microbial community composition and evaluates the feasibility of phytoremediation, along with proposing subsequent measures. Our study employs spatial sequence instead of time-sequenceal sequence to investigate early-stage changes in soil microbes and physicochemical properties in alpine mining land reclamation. We used high-throughput sequencing for the 16S rRNA amplicon study. Over time, soil physicochemical properties improved noticeably. Soil pH shifted from neutral to alkaline (7.04-8.0), while soil electrical conductivity (EC) decreased to 77 μS·cm-1 in R_6a. Cation exchange capacity (CEC) initially decreased from R_2a (12.30-27.98 cmol·kg-1) and then increased. Soil organic matter increased from 17.7 to 43.2 g·kg-1 over time during mine reclamation and restoration. The dominant bacterial community consisted of Proteobacteria (33.94% to 52.09%), Acidobacteriota (4.94% to 15.88%), Bacteroidota (6.52% to 11.15%), Actinobacteriota (7.18% to 9.61%), and Firmicutes (4.52% to 16.80%) with varying relative abundances. Gene annotation of sequences from various reclamation years revealed general function prediction, translation, ribosome structure, cell wall/membrane/envelope biogenesis, nucleotide translocation, and metabolism, along with other related functions. Mine reclamation improved soil fertility and properties, with the R_6a treatment being the most effective. Starting in the 2nd year of reclamation, the effective phosphorus content and the dominance of microbial bacteria, notably the Bacillus content, decreased. Firmicute fertilization promoted phosphorus and bacterial growth. In conclusion, employing a blend of sequencing and experimental approaches, our study unveils early-stage enhancements in soil microbial and physicochemical properties during the reclamation of alpine mining areas. The results underscore the beneficial impacts of vegetation restoration on key properties, including soil fertility, pore structure, and bacterial community composition. Special attention is given to assessing the effectiveness of the R_6a treatment and identifying deficiencies in the R_2a treatment. It serves as a reference for addressing the challenges associated with soil fertility and microbial community structure restoration in high-altitude mining areas in Qinghai-Tibet. This holds great significance for soil and water conservation as well as vegetation restoration in alpine mining regions. Furthermore, it supports the sustainable restoration of local ecosystems.

Changes in Nutrient-Regulated Soil Microbial Communities in Soils Concomitant with Grassland Restoration in the Alpine Mining Region of the Qilian Mountains

In response to the significant ecological damage caused by unsustainable mining practices in the Qilian Mountains, ecological restoration projects have been undertaken in recent years. Analyzing the changes in soil microbial communities during the restoration process of mine meadows helps to reveal the mechanism of the restoration process in alpine mining areas. To explore the characteristics of soil microbial community distribution and their relationships with soil environmental factors during the restoration of alpine grasslands in the Qilian Mountains, we conducted surveys and analyses in two restoration levels low restoration (LR) and high restoration (HR) in the eastern Qilian Mountains, along with an undisturbed natural grassland control (NG). We found that as the degree of high-altitude mining area recovery increases, there were significant increases in vegetation cover, vegetation height, above-ground biomass, vegetation Shannon–Wiener index, soil organic carbon (SOC), soil water content (SWC), total nitrogen (TN), total phosphorus (TP), total potassium (TK), available phosphorus (AP), and available nitrogen (AN). Conversely, soil pH and electrical conductivity (EC) significantly decreased, with soil pH decreasing from 6.93 to 4.13. Restoration of high-altitude mining area grasslands significantly alters the distribution and composition of soil bacteria and fungi, while the impact on soil microbial community changes was not significant. Notably, with increasing recovery level, the dominant bacterial phyla are Acidobacteria and Proteobacteria, while the dominant fungal phyla are Ascomycota and Basidiomycota. These results indicate that changes in vegetation and soil properties both affect the composition of soil microbial communities, with soil properties having a greater influence. Soil fertility and nutrient levels emerge as the primary drivers influencing soil microbial composition communities and the degree of high-altitude mining area grassland recovery.

Energy potential of high altitude mines in Central Asia

Energy potential of high altitude mines in Central Asia

Safety assessment of slope on in-service dump under severe dry–wet cycles at high-altitude

This study aimed to evaluate the safety of dump slopes in high-altitude areas subjected to severe dry–wet cycles. The slope of No. 1 and No. 2 in-service dumps in limestone mining areas for cement in high-altitude mining areas is taken as the research object. The unsaturated soil shear strength and matrix suction distribution equations were imported based on the unsaturated–saturated seepage theory. Therefore, the evolution characteristics of the unsaturated–saturated seepage field in the dump are analyzed by numerical calculation, and the safety state of the dump slope is evaluated. The results indicated the following rules: under the action of four dry–wet cycles, the surface soil of the dump slope changes from an unsaturated state to a saturated state. Furthermore, with the increase in the times of the dry–wet cycle, the maximum vertical displacement of the No. 1 and No. 2 dump slopes increased. The numerical calculations of the maximum cumulative vertical displacement of the slope were consistent with the actual monitoring data. The factor of safety of the dump slope decreased continuously with the increase in the times of dry–wet cycles. Nevertheless, it still met the safety and stability standards. It was concluded that the slope of the in-service dump remains stable after enduring four severe cycles of dry–wet.

Energy potential of mining transport at mines of Kyrgyzstan located at high altitude

Review and Justify use of new alternative way of gold ore transportation on high altitude mining operations in Kyrgyzstan in prime purpose of the study. Glaciers of Kyrgyzstan are main source of fresh water supply in Central Asia. Local ecosystem preservation is important part of metal mining in Kyrgyzstan and specific needs of nomads should be taken in the account. Novelty of study is preliminary assessment of mine in Kyrgyzstan for potential gravity energy by loading and dumping point’s GPS coordinates are taken on site and review of appropriate technologies for ore transportation in order to reduce carbon emissions. Aerial ropeway specific energy consumption formula and recuperating ropeway system from previous studies are reviewed and used in study. Improvement of existing mine operations by improving transportation practices should be further studied. The design and maintenance of haul roads may allow to reduce diesel fuel consumption by 10% and more. Preliminary potential energy for recuperation by aerial ropeway application in Jerooy and Jamgyr gold mines of Kyrgyzstan are identified. Energy recuperating aerial ropeway system with fuel cells can be strategically long-term preferred solution for mines in Kyrgyzstan located in high altitude.

Study on safety and stability of high altitude dump under severe drying-wetting alternation.

This study aimed to reveal the impact of the severe drying-wetting process on the safety and stability of high-altitude dumps. Numerical calculations were conducted for the open mining dump of limestone mines for cement in high-altitude mining areas. The distribution law equation of the matric suction and the shear strength equation were imported for unsaturated soil based on the unsaturated-saturated seepage theory. Therefore, the evolution characteristics of the unsaturated-saturated seepage field and the stability of the dump were studied under severe drying-wetting. The results indicated the following rules: As the intensity of the wetting-drying alternation increased, the surface soil on the dump changed from an unsaturated to a saturated state, the matric suction continued to decrease until it reached zero, the shear strength decreased, and the unsaturated area shrank. The dump slipped under the influence of the drying-wetting alternation, the sliding area was the dump itself, and developed to the deep layer as the intensity of the drying-wetting alternation strengthened. The cumulative settlement value of the dump increased with time and eventually stabilized, and the maximum accumulative settlement value calculated by simulation was in good agreement with the actual monitoring value. The safety factor decreased as the intensity of the drying-wetting alternation increased.

Healthy worker survival effect at a high-altitude mine: prospective cohort observation

Very little is known about the factors of healthy worker survival effect at high-altitude mines. We conducted this cohort observation of the new hires for a high-altitude gold mine in Kyrgyzstan with the aim to ascertain predictors of survival at work. All new hires in 2009 through 2012 for a high-altitude gold mine (3600–4500 m above sea level) were followed up to January 2022. We tested the association of demographic, physiological predictors and diagnoses at the pre-employment screening with non-survival at work in Cox proportional hazards yielding hazard ratios (HR) with their 95% confidence intervals (CI). The cumulative observation time was 5190 person-years. Blood pressure at pre-employment, lung function, the diagnoses of essential hypertension, chronic obstructive pulmonary disease (COPD) or any other analyzed physiological variables were not associated with non-survival at work. However, smoking (HR 1.55; 95% CI 1.10; 2.17) increased the likelihood of non-survival at work, independent of any diagnosis or lowland residence (HR 1.95; 95% CI 1.31; 2.90). Adjusted for covariates and all diagnoses, having chronic rheumatic fever (HR 10.95; 95% CI 2.92; 33.92), hemorrhoids (HR 1.32; 95% CI 1.01; 3.75), adhesive otitis (HR 1.74; 95% CI 1.05; 2.89) or obesity (HR 1.71; 95% CI 1.01; 2.88) were associated with non-survival at work with time. This prospective observation of new hires for a high-altitude mining operation demonstrated that selected diagnoses, smoking and lowland residence elevated the risk of early exit in prospective workers.

Pulmonary Capacity, Blood Composition and Metabolism among Coal Mine Workers in High- and Low-Altitude Aboveground and Underground Workplaces.

(1) Background: While previous studies revealed how underground mining might adversely affect the cardiopulmonary functions of workers, this study further investigated the differences between under- and aboveground mining at both high and low altitudes, which has received little attention in the literature. (2) Methods: Seventy-one healthy male coal mine workers were recruited, who had worked at least 5 years at the mining sites located above the ground at high (>3900 m; n = 19) and low (<120 m; n = 16) altitudes as well as under the ground at high (n = 20) and low (n = 16) altitudes. Participants’ heart rates, pulmonary functions, total energy expenditure and metabolism were measured over a 5-consecutive-day session at health clinics. (3) Results: Combining the results for both above- and underground locations, workers at high-altitude mining sites had significantly higher peak heart rate (HR), minimum average HR and training impulse as well as energy expenditure due to all substances and due to fat than those at low-altitude sites. They also had significantly higher uric acid, total cholesterol, creatine kinase and N-osteocalcin in their blood samples than the workers at low-altitude mining sites. At underground worksites, the participants working at high-altitude had a significantly higher average respiratory rate than those at low-altitude regions. (4) Conclusion: In addition to underground mining, attention should be paid to high-altitude mining as working under a hypoxia condition at such altitude likely presents physiological challenges.

The Effect of Chronic Intermittent Hypobaric Hypoxia on Sleep Quality and Melatonin Serum Levels in Chilean Miners.

High-altitude mining is an important economic resource for Chile. These workers are exposed to chronic intermittent hypobaric hypoxia (CIHH), which reduces their sleep quality and increases the risk of accidents and long-term illnesses. Melatonin, a hormone produced by the pineal gland, is a sleep inducer that regulates the circadian cycle and may be altered in populations subjected to CIHH. This work aimed to assess the relationship between altitude, sleep quality, and plasma melatonin concentrations in miners with CIHH exposure. 288 volunteers were recruited from five altitudes (0, 1,600, 2,500, 3,500, and 4,500 m). All volunteers worked for 7 days at altitude, followed by 7 days of rest at sea level. We performed anthropometric assessments, nocturnal oximetry, sleep quality and sleepiness surveys, and serum melatonin levels upon awakening. Although oxygen saturation progressively decreased and heart rate increased at higher altitudes, subjective perception of sleep quality was not significantly different, and sleepiness increased in all groups compared to population at sea level. Similarly, melatonin levels increased at all assessed altitudes compared to the population at sea level. These data confirm that sleep disturbances associated with CIHH increase morning melatonin levels. Therefore, this hormone and could potentially serve as a biomarker of sleep quality.

The effect of oxygen supply and oxygen distribution on single-head tunnel with different altitudes under mixed ventilation

Hypoxia plays a major role in limiting the construction of the high-altitude mine. Understanding the effect and the distribution of diffused oxygen supply at different altitudes is the premise for the design of a mine with oxygen supply system and the full utilization of oxygen resources. For the optimal design of an oxygen supply mode and ventilation system, a multi-component fluid model of the diffused oxygen supply of a single-head tunnel was developed. This study reveals the variation law of the average oxygen mass fraction at different altitudes. The relationship between the distance from the heading face and the oxygen mass fraction at each altitude was fitted. The results show that the distribution of oxygen mass fraction in a single head tunnel at different altitudes presents a similar trend of increasing first and then decline. In addition, the change of the average oxygen mass fraction with the increase of altitude is not linear, and the dispersion loss is larger in high-altitude areas. The largest oxygen enrichment area is distributed at the altitudes of 4000–4500 m. This study provides theoretical support for improving the hypoxic environment of high-altitude metal mines excavation work.

Filling Treatment of Surface Subsidence Resulted From Underground Mining in a High-Altitude Mine

In the process of filling the goaf of Huashugou copper mine, the filling aggregate was the mine’s self-produced copper flotation tailings. The physical and chemical property tests showed that the tailings were relatively fine, and the cumulative contents of the 7.5, 15, 80, and 90 μm particles were 56.99, 79.46, 99.88, and 100%, respectively. PSA42.5 Portland slag cement was selected as the cementing material for the tests. The amount of finely ground blast furnace slag added to the cement was 20–50%. The filling test blocks of all proportions were demolded within 24–36 h, and the integrity of the formed filling bodies was satisfactory. Among them, the uniaxial compressive strength of the test block formed by the filling slurry with a tailings-to-cement ratio of 3/1 and a concentration of 74% after 3, 7, 28, and 60 days reached 0.833, 2.026, 4.520, and 6.560 MPa, respectively. The strengths of the other filling blocks also met the engineering design requirements. Based on the statistical regression analysis method, the influences of the slag cement content χ₁ and the tailings water content χ₂ on the filling body’s strength Ϭ were analyzed. The regression calculation also considered the interaction between χ₁ and χ₂, and the obtained multiple nonlinear regression model successfully predicted Ϭ. In production and application, the large density of tailings would accelerate their settling, which could easily cause blockage during the transportation of filling slurry through the pipeline. Regarding a series of existing filling materials and technical conditions, the filling process investigated in this study overcomes several unfavorable conditions. Using advanced and reliable technology and an industrial filling pump with a delivery pressure of 10 MPa, the prepared filling slurry concentration was 68–72% and the flow rate was 56–79 m3/h. The tailings and PSA42.5 Portland slag cement combined quite well. The filling body in the goaf demonstrated excellent homogeneity, and the various industrial indicators met the technical requirements for mining deposits. The preparation of high-quality filling materials with a smooth filling process has played a positive role in the prevention and treatment of surface mountain cracks and collapse during underground mining in high-altitude areas.

Assessment of operational reliability of power supply to developing ore mining areas at a high-altitude mine

Development of new deposits and modernization of existing mining enterprises in order to improve their efficiency are the priorities for the development of tungsten-molybdenum resource sector. In the modernization of mining productions, attention is paid to all technological processes and engineering systems, transformation of which should be aimed at improving economic performance, including reliability. Research of power supply systems of mining enterprises and modes of their operation is an urgent task, as this type of engineering support of mining works, auxiliary processes and facilities determines competitiveness of an enterprise as a whole. In the course of research, an assessment of operational reliability of power supply of developing ore mining areas at a high-altitude mine of the Tyrnyauz deposit (Kabardino-Balkaria) was performed. It was found that under the existing scheme of separate power supply of 6 kV networks from substations, the full ground fault currents for these networks are respectively: I030=17.5 A and I0116 =12.2 A and reach the limiting values at which it was possible to disconnect them by disconnectors (the limiting current was 20 A). A formula for total ground fault current in 6 kV underground networks was recommended. It was shown that reliability of power supply in the above mine, as well as the level of danger of electric shock in electrical installations depended largely on the number of singlephase ground faults. On the basis of the theoretical and experimental research, the solutions to improve the operation of electrical networks, taking into account the structure and modes of operation of a highaltitude mine were developed.

Health Effects of Chronic Intermittent Hypoxia at a High Altitude among Chilean Miners: Rationale, Design, and Baseline Results of a Longitudinal Study.

This study aims to assess the health effects on mining workers of exposure to chronic intermittent hypoxia (CIH) at high- and very high-altitude mining compared with similar work at lower altitudes in Chile, and it also aims to constitute the baseline of a 5-year follow-up study. We designed a cross-sectional study to assess health conditions in 483 miners working at 2 levels of altitude exposure: 336 working at a very high or high altitude (HA; 247 above 3900-4400 m, and 89 at 3000-3900 m), and 147 below 2400 m. Subjects were randomly selected in two stages. First, a selection of mines from a census of mines in each altitude stratum was made. Secondly, workers with less than 2 years of employment at each of the selected mines were recruited. The main outcomes measured at the baseline were mountain sickness, sleep alterations, hypertension, body mass index, and neurocognitive functions. Prevalence of acute mountain sickness (AMS) was 28.4% in the very high-altitude stratum (P = 0.0001 compared with the low stratum), and 71.7% experienced sleep disturbance (P = 0.02). The adjusted odds ratio for AMS was 9.2 (95% confidence interval: 5.2-16.3) when compared with the very high- and low-altitude groups. Motor processing speed and spatial working memory score were lower for the high-altitude group. Hypertension was lower in the highest-altitude subjects, which may be attributed to preoccupational screening even though this was not statistically significant. Despite longer periods of acclimatization to CIH, subjects continue to present AMS and sleep disturbance. Compromise of executive functions was detected, including working memory at HA. Further rigorous research is warranted to understand long-term health impacts of high-altitude mining, and to provide evidence-based policy recommendations.

Bolivian migration and ethnic subsidiarity in Chilean sulphur and borax high-altitude mining (1888–1946)

ABSTRACT Bolivian migration in borax and sulphur high-altitude mining was fundamental in sustaining industrial capitalism in northern Chile. In this paper, we quantify and characterize Bolivian migration in the border mining camps of the municipality of Ollagüe, through the analysis of 335 migratory files, dating from 1888 to 1946. We focus on the Bolivian presence in eight villages and camps involved in sulphur and borax mining. We present the entry periods of Bolivian workers, as well as their origin, trade and profession, gender, marital status, age, and literacy. Results give an account of the central role played by the Bolivian migrant labour force for the development of non-metallic and high-altitude mining industries in the region. It is concluded that the capitalist expansion in the Chilean border was sustained by an ethnic subsidiarity of an international subordinate workforce.

АНАЛИЗ СОСТОЯНИЯ ИЗОЛЯЦИИ ЭЛЕКТРООБОРУДОВАНИЯ ГОРНО-МЕТАЛЛУРГИЧЕСКИХ КОМБИНАТОВ

The paper presents the results of theoretical analysis and mathematical processing of experimental studies of the insulation state of individual elements of the same type of sections of 0.4 kV electric networks in underground workings conducted at the mining and processing mines at heights of workings up to 1000 m above sea level. The studies were carried out according to a single method in order to identify the effect of highlands on the insulation state of individual elements of 0.4 kV networks. It is recommended to complete scraper winches, fans and other mechanisms of high-altitude mines with organosilicon-insulated engines or with front coatings filled with top coat varnishes similar to excavator engines. A similar situation is noted with the launcher. More than 50 % of all the equipment of high-altitude mines have an active insulation resistance of less than 20 mOhm. A higher asymmetry of the total and active insulation resistance of launchers is noted. It is recommended to use silica gel to reduce air humidity inside the shells of the launcher...

Study on the influence law of ventilation conditions on heat loss in a roadway of high altitude mine

It is necessary to study the heat loss law along the roadway of high altitude mines for the design of anti-freezing ventilation system. With a mine adit as the research object, this article used FLUENT software to carry out numerical simulations to study the influence of altitude and ventilation conditions on the heat loss along the roadway. Using the uniform design and regression analysis method, the prediction formulas of heat loss with different influential factors were fitted out. The results showed that the heat loss along the roadways has a negative exponential correlation with altitudes while is positively correlated with inlet airflow volume and convective temperature difference. The main factors impacting the heat loss along the roadway in a descending sequence was as follows, convective temperature difference, airflow volume, roadway length, and altitude. When given a confidence interval of 95%, the regression model of the heat loss parameter along the roadway is highly significant. With the fitting error controlled within 15% which can meet the needs of engineering prediction.

Spanish Colonial Networks of Production: Earthenware Storage Vessels from The Peruvian Wine Industry

Following Spanish conquest, wine and brandy production flourished in the Moquegua Valley in southern Peru. Alcohol products both served local demand and were shipped to high altitude mining centers. Wine was fermented and stored in tinajas, large earthenware ceramic vessels. Reporting analyses of paste composition of 70 tinajas using portable XRF technology, we examine the production of these vessels. Our results suggest that tinaja manufacture was localized in Moquegua but that valley wineries participated in varied production systems. Our analysis indicates that more sophisticated sourcing methods would refine the relationship among tinaja pastes, locally available clays, and production networks.

Simulation Study on the Dynamic Ventilation Control of Single Head Roadway in High‐Altitude Mine Based on Thermal Comfort

Dynamic ventilation control based on the concept of thermal comfort is proposed and applied to single head roadway in high‐altitude gold mine in Qinghai. Hourly thermal comfort values are determined for typical working conditions, and a thermal comfort curve is generated. The values are adjusted based on the external environment and the changes in the miners’ thermal comfort. The Fluent software is used to simulate the temperature field and wind speed field of the tunnel roadway at three heights, and the results are used to fit the thermal comfort curve in the roadway. The results show that the thermal comfort is lowest at a roadway height of 1 m and a longitudinal length of 16 m because the wind speed is the highest and the temperature is lowest at these locations. When the dynamic ventilation control is used, the optimal thermal comfort levels can be determined for the locations in the single head roadway.