Mined-out Area Research Articles

Вариативность поверхностных горизонтов почв города Тюмени (Россия)

Urbanization is one of the main trends of the modern world. The growth of the urban population, and, as a consequence, the increase in the area of urban landscapes, leads to a significant transformation of the environment due to comprehensive human economic activity or anthropogenesis. Such changes affect not only natural landscapes as a whole, but also their individual components, such as soil cover. Anthropogenically transformed soils occupy significant areas within urbanized territories. The nature of the anthropogenic impact on soils is determined by the type of land use and is reflected in the profile of urban soils in the form of formation of corresponding anthropogenic horizons or changes in the properties of surface horizons. Field work was carried out within the boundaries of the city of Tyumen (57°09′ N, 65°32′ E), including both the core of dense urban areas and peripheral agricultural and recreational areas. The object of the study in this work is anthropogenically modified soils of the city of Tyumen. The description and diagnostics of horizons and characteristics were carried out on the basis of the “Classification and Diagnostics of Soils of Russia” [2004], taking into account proposals for the introduction of urban soils into the soil classification system of Russia. The research methods included morphological analysis of soils, determination of acidity, organic carbon content by the titrimetric method, soil texture by sedimentation method with pyrophosphate preparation. Statistical analysis of the data was carried out using the STATISTICA 12 “StatSoft” package (USA). The results showed that natural surface horizons are typical only for undisturbed soils of the recreational area. The soils of other functional zones demonstrated signs of anthropogenic impact, which were expressed in the form of changes in both the soil profile as a whole and surface horizon. The direction and intensity of anthropogenic impact correspond to the severity of the transition from natural to anthropogenic landscapes. The reaction of the surface horizons varies from acidic to strongly alkaline. The largest area within the city is occupied by alkaline soils. The Corg values fluctuate within 0.01-22.84%, with an average value of 2.7%. Loamic and siltic varieties predominate, among which silt loams are the most widespread. The composition of the major oxides is consistent with the soil texture. The contents of Fe2O3 and Al2O3 vary between 0.7-7.7 and 1.5-13%, their increased values are typical for soils on cover and loess-like loams. The SiO2 content in most urban soils is 60-70%. Within the urban area of Tyumen, 5 districts are distinguished according to with the morphology and properties of surface soil horizons. In the city center, urban stratified soils on sandy and silty loamy technogenic deposits with elevated pH and average content of Corg predominate. The northern part of the city is occupied mainly by peat soils on the site of mined-out areas of the Tarman bog massif with an alkaline reaction and а high content of Corg. In the western part on the city periphery, agrogenically transformed and postagrogenic soils with slightly acidic and neutral reaction and average content of Corg on loess-like loams can be found. In the northeast of the city alkaline agricultural soils predominate. In the southeastern part within the lacustrine-alluvial deposits, slightly altered soils with low pH values and low Corg content can be found.

Are fluorite mines prone to high concentrations of radon gas inside? The case of the Lújar mine in Órgiva (Granada, Southeast Spain)

The Sierra de Lújar, located in the south of Granada (Spain), hosts one of the few currently active underground fluorite mines in Spain. Considering that high concentrations of radon gas, which is the second leading cause of lung cancer after tobacco, can occur in underground workplaces, the concentration of radon gas inside a fluorite underground mine has been measured, in order to prevent health risks to workers. QueryAlthough no significant concentration of radioactive elements has been detected in the geochemical analysis, the radon gas concentration values measured ranged between 28 and 1211 Bq m−3, and there were important variations, depending on the area of the mine. Some values exceed the limits established by European regulations. Despite these high values, the annual effective dose (E) ranges between 0.13 and 5.71 mSv, in most cases being below 3 mSv, which is the recommended value in underground mines. Improvement in the ventilation of main galleries, especially in the benefit plan area (level 423), the isolation of mined-out areas using bulkhead, continuous monitoring of radon concentration, and periodic health controls to workers are estimated as the main mitigation measures to take into consideration. The findings from this research suggest that workers in this underground fluorite mine may face substantial risk of receiving radon doses that could meet or surpass the recommended thresholds established by European regulations. This underscores the imperative for additional investigations into radon levels within underground operations in Spain.

Experimental study on deformation and failure of a mining slope under the action of rainfall

On 28 August 2017, a mining slope collapse in Pusa Village, Guizhou Province, China, resulted in the release of ~8600 m3 of earth and rock, leading to 35 fatalities. The deformation and failure mechanisms of the mining slope under the influence of rainfall was studied by a physical model test, using the Pusa Village collapse as an example. Data were collected through strategically placed monitoring points in a physical model, forming the basis for a quantitative analysis of slope deformation and failure patterns. The tested results revealed that sequential mining and rainfall activities induce progressively increasing stress variations, exhibiting a cyclical pattern of stress concentration, relaxation, and stabilization. Mining activities initiated the formation of tension and separation fractures within the model, which were subsequently exacerbated by rainfall. Rainwater infiltrating through these fractures and geotechnical bodies resulted in a more pronounced increase in water content in the upper part of the model than in the lower part. Displacement values within the model progressively increased with ongoing coal seam mining, primarily occurring in the mining area's roof and extending to the model's top following rainfall. The failure mode of the Pusa slope under combined mining and rainfall conditions is characterized by the following sequence: bending-pulling-subsidence-creep-dumping. The deformation and failure processes can be categorized into four stages: mining-induced disturbances, fractures extension and extension, formation of a potential collapse surface, and destabilization failure.

Preparation and characteristic study of the hydrogel of coal spontaneous combustion environmental protection

In order to solve the problem of spontaneous combustion of coal in mined-out areas, a new type of P/S/T/H environmentally friendly hydrogel was designed by using polyvinyl alcohol, sodium alginate and di(triethanolamine) titanate diisopropyl to form a gel system and adding the environmentally friendly material hybrid shell bio-filler. The formulation of P/S/T/H gel was studied by orthogonal experiment, and the forming time was precisely controlled. The synthesis mechanism and flame-retardant properties of the gels were investigated by various experimental methods. The results show that: There are folds and three-dimensional pore structures inside the P/S/T/H gels, and the two cross-linked networks strengthen the stability of the gels. Compared with WG gel and single cross-linked network gel, P/S/T/H gel has the best water retention, water absorption/salt resistance and flame-retardant effect. The water retention rate of P/S/T/H gel is still as high as 20% after 12 h, the water-absorbing multiplicity is more than 400 after 90 min, and the salt-resistant multiplicity is 54 after 90 min. When P/S/T/H gel is added to the coal samples, the combustion end temperature lags 8.4 °C, the heat release is reduced by 19.9%, the average CO inhibition rate is 45.9%, the maximum heat release rate is reduced by 20.1 KW/m2, the total heat release rate is reduced by 36.6%, and the maximum flue gas inhibition rate is 87.1%. Therefore, the highly efficient and environmentally friendly P/S/T/H gel is expected to play an important role in the work of fire prevention in mined-out areas.

Green and efficient recovery of poly metals from converter sludge through reduction roasting and preparation of backfill from tailings

Converter sludge (CS) is a type of solid waste containing iron and poly metals that are not thoroughly utilized yet. A novel process combining reduction roasting with waste backfill was designed to optimize the recovery of poly metals and investigate the feasibility of waste tailings as mine backfill. The dust contained 66.57 % zinc oxide, which could be sold as a by-product to zinc smelters, with 92.65 % lead recovery and 95.36 % zinc recovery. The powdery reduced iron (PRI) was suitable for steelmaking, and 91.45 % of iron was recycled. During reduction, lead and zinc in CS were reduced and then volatilized, and iron recovery was enhanced by the formation and growth of metallic iron. The coarsening of metallic iron was dominated via surface and volume diffusion, and the average activation energy was 966.48 kJ/mol. The slump, yield stress, and 90-day compressive strength of the backfill prepared from tailings were 208 mm, 106 Pa, and 1.11 MPa, respectively, indicating that it could be used as the backfill for underground mined-out areas. This process presents excellent application prospects and provides innovative ideas for comprehensive and green disposal of CS.

Research on Sustainable Development of Mining Goaf Management Based on Economic Models

The sustainable development of mines has been the focus of attention in recent years. In China, there are a large number of untreated mined-out areas, and a series of disasters caused by the instability of the goaf will bring heavy blows to people’s safety and financial resources. Filling treatment will lead to increasing costs and decreasing profits, which will seriously reduce the motivation of mining enterprises and even lead to a moral hazard. Therefore, the analysis of the economic benefits of goaf control plays a vital role in the sustainable construction and long-term development of mines. This paper proposed the mined-out area treatment economic model. The proposed method employs the guiding philosophy of the newsboy model to create a mathematical economy model that provides the basis for a goaf management mode for mines. The following research results were obtained: (1) The economic model of the mined-out area backfilling treatment is constructed, which is classified as three different modes. (2) Combined with mathematical derivation and simulation, the influence of relevant variable parameters on each type of filling mode is discussed. (3) Various types of goaf filling treatment mode are compared with a non-filling scheme (benchmark mode), to provide theoretical support to help mining enterprises choose appropriate filling schemes. The results show that the economic model of mined-out area management provides the optimal mode for mined-out area filling, and the balance of tailings and ultra-high-water filling material procurement is realized, resulting in maximum profits. In this paper, we explain how the use of economic thinking has an important impact on the sustainable development of safety goaf management.

Groundwater Vulnerability Assessment and Protection Strategy in the Coastal Area of China: A GIS-Based DRASTIC Model Approach

Groundwater vulnerability reflects the risk level of groundwater contamination and its self-repairing ability, as well as its sustainability for use. Therefore, it provides significant scientific support for implementing measures to prevent groundwater contamination, especially in coastal areas. In this study, considering the lithology of vadose in valley plains and the extent of karst subsidence areas, a GIS-based DRASTIC model was employed to assess groundwater vulnerability in Tangshan City, a coastal area in China. The assessment results were presented and mapped using GIS, based on a comprehensive evaluation of seven parameters, including “Depth of groundwater, Vertical net recharge, Aquifer thickness, Soil media, Topography, Impact of vadose zone, and Hydraulic conductivity”. The identified groundwater vulnerability zones included the highest, higher, moderate, low vulnerability those four zones, which accounted for 4%, 53%, 25%, and 18%, respectively. In addition, according to the results of field investigation, the karst subsidence area and the mined-out coastal area were directly classified as the highest vulnerable areas and covered 1.463 km2; more attention is required here in subsequent groundwater protection processes and strategies. Finally, the groundwater pollution index was used to validate the groundwater vulnerability distribution results, and these two were in high agreement, with an R2 coefficient of 0.961. The study is crucial for the rational utilization and protection of water resources in Tangshan City.

Preparation of phosphogypsum-based cemented paste backfill and its environmental impact based on multi-source industrial solid waste

Cemented Paste Backfill (CPB) technology is considered as an effective method to solve the serious problems caused by the solid wastes’ accumulation, and to mitigate the risk of mined-out areas. However, the serious influence on the environment and higher pro-treating costs of solid wastes limits their application in CPB. Meanwhile, due to the high carbon emissions and high costs of Portland cement, its use as a binder in CPB is also limited. This paper used raw phosphogypsum (PG) as filler. Yellow phosphorus slag (YPS), fly ash (FA), steel slag (SS), and Portland cement were mixed to make a composite binder. Solid wastes addition was ranged from 80% to 98%. The feasibility of CPB co-preparation with a high percentage of multi-source industrial solid waste was verified by analyzing the performance and environmental impact of CPB produced with different percentages of solid wastes. The results showed that a higher PG addition was harmful to the property of CPB, leading to a lower fluidity, longer setting time, and weaken strength. However, the development and use of composite binder offset those negative aspects effectively. Composite binder is a CaO-rich binder that provides an alkaline environment for hydration reactions which enhanced CPB strength. Because its unconfined compressive strength reached to 3.1 MPa ∼ 19.5 MPa after 60 d’s curing. This will provide a highly strengthen support to the mine to be filled with CPB, thus hindering its re-collapse. The gradually increased hydration products observed from the microstructural characterization further corroborated the strength development path of the CPB. Moreover, the adsorption and precipitation process in the alkaline system contributed to the stabilization of the contaminants from those solid wastes. Therefore, the CPB technology based on the multi-source industrial solid waste is considered as a green, promising, and cost-saving choice on supporting safe mining and mitigating environmental pollution.

Experimental Research on Application of Waste Concrete Powder-Waste Brick Powder-Cement Grout for Foundation Reinforcement in Mining Goaf.

Combined with a strategic policy for the recycling of construction waste, this paper puts forward a programme for treating a goaf foundation with waste concrete powder, waste brick powder, and cement grout (BCP cement grout). The BCP cement grout is prepared by replacing part of the waste concrete powder with waste brick powder, and the changeable rule of the setting time, water separation rate, stone rate, and viscosity of the grout with different rates for replacement are studied. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are carried out. The mineral composition is analyzed and the microscopic mechanism is studied. The results show that the ratio of BCP cement grout developed by the experiment is reasonable; the unit cost is less than 160 yuan/t, which is 40% lower than that of pure cement grout; and both a good economic effect and good environmental effect are obtained. It has the advantages of low water separation rate, high stone rate, and low viscosity. When the ratio of cement powder: waste concrete powder: waste brick powder is 3:5:2 or 3:6:1, the 28 d compressive strength of the stone body is more than 2 MPa, meeting the filling requirements for a goaf foundation. It is not only technically feasible but also economically reasonable to apply construction waste powder to fill the goaf foundation. Recycling and utilizing construction waste can also achieve the ecological restoration of mined-out areas, highlighting the ecological benefits.

Monitoring of barricade pressure during the entire backfilling process for a high iron mine stope

The stability of the backfill barricade is an important foundation for safe mining production. The backfill material is transported to the underground mined-out area. During the backfilling process, it is difficult to directly monitor the curing process of backfill body and its lateral load on barricades. This severely affects the accurate formulation of the mining and backfilling strategy as well as effective control of associated costs. In order to investigate the change law of pressure on barricade, a continuous monitoring experiment was conducted by installing pressure sensors inside the barricade. The results indicated that the pressure on barricade showed an initial increase followed by a subsequent decrease and eventual convergence towards zero with the increase in backfill height and curing time. A barricade pressure prediction model was established for discontinuous backfilling conditions using a fitting method that characterizes the relationship between backfill height and barricade pressure through a Gaussian function. Finally, from both on-site monitoring and theoretical analysis, it was jointly demonstrated that the continuous filling of Luohe iron ore mine quarry has safety and feasibility.

REHABILITATION OF MAN-MADE FORMATION OF ABANDONED COPPER PYRITE DEPOSITS ON THE EXAMPLE OF LEVIKHINSKY MINE (MIDDLE URALS)

Link for citation: Rybnikova L.S., Rybnikov P.A., Navolokina V.Y. Rehabilitation of man-made formation of abandoned copper pyrite deposits on the example of Levikhinsky mine (Middle Urals). Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 137-150. In Rus. The relevance of the research is related to the need to rehabilitate of abandoned copper pyrite deposits affected by acid mine waters and justify measures to clean up the existing clarification pond. The main aim is to study the sludge composition and justify the measures to reduce the environmental load on the hydrosphere. Objects: clarification pond and neutralization sludge of the Levikhinsky copper pyrite mine acid mine waters. Methods. Laboratory studies of water and bottom sediments were carried out using atomic emission and mass spectral analysis; methods of flame emission spectrometry, flame atomic absorption, photometric method with Nessler's reagent, titrimetric, mercumetric and potentiometric methods; mass spectrometry with ionization in inductively coupled plasma and gravimetric method. Results. Sludge samples are dominated by sulfates (gypsum and bassanite), iron oxides and hydroxides (goethite), carbonates (calcite), clay minerals (mainly hydromica) and chlorine-containing salts (carnallite). The chemical composition of the sludge is dominated by oxides of iron, sulfur and calcium. The analysis of water and acid extracts showed that up to 24 elements belonging to hazard classes 2, 3 and 4 can be leached from the sludge in concentrations exceeding the maximum allowable values for fishery water bodies. Several options for the use of sludge from the clarification pond were analyzed: reclamation of waste rock dumps and substandard ores; backfilling of mined-out area of quarries; production of building materials; extraction of components; storage of sludge in geotubes (Geotube). The most rational is the disposal of sludge as the production of building materials on the basis of a public-private partnership, the implementation of which will allow the state and the private sector to derive mutual benefit.

New model of negative carbon utilization in coal mine goafs and its feasibility and prospects for application

Over hundreds of years, the global coal mining has created 24.236 billion cubic meters of underground goaf, which not only wastes billions of square meters of land resources but also poses significant safety hazards and environmental risks. Combining the treatment of mined-out areas with carbon dioxide (CO2) storage can provide the new idea for solving the above problems in a low-carbon way. Therefore, based on an analysis of the status of mined-out areas and CO2 storage principles, this paper proposes a method of using high-water materials to solidify supercritical CO2 and fill mined-out areas. The feasible, safety and carbon fixing capacity of using high-water materials to solidify CO2 and fill mined-out areas has been proved by theoretical analysis and indoor experiment. Combining the estimated underground mined-out area space of major coal-producing countries globally, proving that solidifying and sealing CO2 in mined-out areas has significant application prospects. Finally, the issues and technical difficulties faced in promoting the use of high-water material to solidify supercritical CO2 and fill mined-out areas are pointed out. The research results have important significance for major coal-producing countries worldwide to achieve "carbon peak and carbon neutrality".

Investigation on the Height of Fracture Zone in Goaf of Steep Coal Seam Based on Microseismic Monitoring

The height of the fracture zone in the mined-out area is the basic parameter for controlling mine strata, preventing and controlling mine water, and arranging drilling holes for high-level gas extraction. Aiming at the development law of fracture zone in the steep seam and the limitation of traditional drilling inspection method, microseismic monitoring technology is used to investigate the height of fracture zone in goaf. Taking the 3103 south working face of a mine in Sichuan as an example, the scheme of microseismic monitoring and data collection of the working face is worked out. Through data analysis and processing, the range of the fracture zone in the goaf is 6.8 m– 34.2 m, and compared with the numerical simulation analysis results, the relevant results are basically consistent. It provides a new technical means for the investigation of “three zones” of overlying strata in the goaf of a steep seam.

Dynamic Monitoring and Analysis of Mining Land Subsidence in Multiple Coal Seams in the Ehuobulake Coal Mine Based on FLAC3D and SBAS-InSAR Technology

Aiming at the land subsidence problem caused by multiple coal seam mining in the Ehuobulake Coal Mine, this paper, considering the geological conditions of the first and fifth layers of coal, adopts the method of combining FLAC3D numerical simulation and SBAS-InSAR technology to analyze the dynamic evolution law of land subsidence amount and range under multiple coal seam repeated mining conditions. The reliability of the technology is verified by the field GPS monitoring data. The results show that, under the mining condition of multiple coal seams in the Ehuobulake Coal Mine, the land subsidence presents obvious asymmetry, and the size and range of the land subsidence in the mining area further increase due to the mining of lower layer coal. FLAC3D simulation results show that the maximum land subsidence is −211.8 mm. The results of SBAS-InSAR monitoring show that the maximum land subsidence is −225 mm, and the land subsidence obtained by the two methods has a high degree of fitting. The method of combining FLAC3D and InSAR technology can accurately and reliably monitor and analyze the land subsidence under the repeated mining of multiple coal seams in the mining area. It can provide effective guidance for the stability analysis of mined-out areas and the prediction of the influence of repeated mining on ground deformation.

Long-term evolution of overlying rock fractures in mined-out areas and its effect on gas flow conductivity

Abandoned mines are often closed for long periods, and the overlying rock in mined-out areas is subjected to creep due to constant stress, which affects the overlying rock fracture morphology. The fractures in these rocks have a conductive effect on the gas flow, and previous studies less consider the influence of the long-term evolution process of the fractures on the gas distribution in these areas. Long-term experiments were conducted using a physical similarity experimental model of the mined-out area. To further explain the evolution law of the overlying rock displacement and fracture fields, a method for quantifying the percentage of the fracture field of the overlying rock based on computer image recognition technology is proposed. The results show that the long-term evolution of the overlying rock fractures have the characteristics of transfer and closure, and the change process determines the gas flow trajectory of overlying rock. The long-term evolution of the overlying rock is clarified, which incorporates the three-stage development of the delamination fractures and the stage density increase of the broken fractures. The gas storage capacity of the overlying rock first increases, then decreases, before stabilizing, and the gas diffusion capacity gradually increases. The gas distribution range fluctuates and increases with the evolution of the overlying rock fractures at different times. The time-varying law of the long-term evolution of overlying rock fractures in the mined-out area is explained and theoretical support is provided for clarifying the time-varying law of gas distribution in the overlying rock.

Abandoned coal tunnel survey by multiscale window analysis of Rayleigh waves

Abandoned coal tunnels (ACTs) pose risks to coal mine safety by accumulating gas and water, causing surface subsidence, and endangering infrastructure. Accurate detection of ACTs is vital for advanced prediction and geotechnical hazard warnings. Seismic methods, particularly the surface-wave method, have demonstrated reliability in detecting shallow buried tunnels within complex geological environments, but improvements in accuracy and resolution are still needed. In this paper, we suggest utilizing the multiscale window analysis of surface waves (MWASW) method for ACT surveys. We conduct a synthetic test and a real-world case study to evaluate the feasibility and validity of this approach. The synthetic test on a 2D ACT model reveals that MWASW can reconstruct anomalous structures and identify the presence of an ACT, while also highlighting some limitations of the method. In a real-world scenario, we applied MWASW to a multi-survey line dataset from a coal mine in Shanxi Province, China. The resulting meter-scale resolution pseudo-3D S-wave velocity structure uncovers a primary ACT and two sub-ACTs buried at approximately 60 m, offering valuable insights into their morphology and orientation. To our knowledge, this is the first application of the MWASW method in such a case study, indicating its potential as an emerging alternative for characterizing complex near-surface media, such as abandoned coal tunnels or mined-out areas in coal fields.

Transport mechanism and control technology of heavy metal ions in gangue backfill materials in short-wall block backfill mining

Short-wall block backfill mining can effectively control the movement of overlying strata, prevent water loss and utilize waste gangue materials. However, heavy metal ions (HMI) of gangue backfill materials in the mined-out area can be released and transported to the underlying aquifer, causing pollution of water resources in the mine. Accordingly, with short-wall block backfill mining technology, this study analyzed the sensitivity of gangue backfill materials to the environment. The pollution mechanism of gangue backfill materials to water resources was revealed, and the transport rules of HMI were explored. The regulation and control methods of water pollution in the mine were then concluded. The design method of backfill ratio for comprehensive protection of overlying and underlying aquifers was proposed. The results show that the release concentration of HMI, the gangue particle size, the floor lithology, the burial depth of the coal seam, and the depth of the floor fractures were the main factors that affected the transport behaviors of HMI. After long-term immersion, HMI of gangue backfill materials underwent hydrolysis and were released constantly. HMI were subjected to the coupled action of seepage, concentration, and stress and then driven by water head pressure and gravitational potential energy to transported downward along the pore and fracture channels in the floor with mine water as the carrier. Meanwhile, the transport distance of HMI increased with increasing release concentration of HMI, the permeability of the floor stratum, and the depth of floor fractures. Still, it decreased with increasing gangue particle size and the burial depth of the coal seam. On that basis, external-internal cooperative control methods were proposed to prevent the pollution of gangue backfill materials to mine water. Furthermore, the design method of the backfill ratio for comprehensive protection of overlying and underlying aquifers was proposed.

Assessing the stability of high-level pillars in deeply-buried metal mines stabilized using cemented backfill

Obtaining a reasonable assessment of the stability of high-level pillars stabilized using cemented backfill is particularly important when designing deeply-buried metal mines. This research determined the average vertical stress in high-level pillars in deeply-buried metal mines and also their strength when subjected to the confining pressure generated by cemented backfill. An expression was thus proposed for the stability of the cemented-backfill-stabilized high-level pillars in deeply-buried metal mines. The results show that the improved formula for estimating the strength of the high-level pillar gives a better reflection of the impact of on-site size and shape effects on the strength of the high-level pillars. The strength of a high-level pillar subject to on-site size effects was obtained by considering the compressive strength of the rock-mass of the pillar under confining pressure provided by the cemented backfill body in the deeply-buried mine. The shape effect was taken into account by considering that the ratio of the effective width to the height of the high-level pillar modifies its strength. At the same time, the concept of load transfer distance was introduced to determine the average vertical stress in the high-level pillar. This method effectively improves the tributary area method which overestimates the average vertical stress in the high-level pillar. When mining the ore body inside a pillar's zone of influence, the area of the orebody excavated should not exceed 0.80 (otherwise it will cause a significant increase in the average vertical axial stress in the high-level pillars). The new method proposed in this study allows the stability of high-level pillars stabilized using cemented backfill to be assessed when an insufficient amount of large-scale in situ testing has been conducted in a deeply-buried metal mine. It also provides a fast, economical, and reliable method for assessing the stability of mined-out areas in deeply-buried metal mines.

Identification of Ground Deformation Patterns in Coal Mining Areas via Rapid Topographical Analysis

Coal mining inevitably brings some negative impacts, such as surface subsidence, aquifer breakage, and land degradation, to the eco-geological environment in the mining area. Among these impacts, coal mining-induced ground deformation is the most serious and has threatened the geological, ecological, and human settlement securities of mining areas. Efforts existing in the literature apply to ground deformation identification in mined-out areas at the meso-/micro and short-time scales. However, when looking back at coal mining history, there are few ways to quickly and accurately quantify ground deformation at the regional and long-time scales. In this context, we propose a method for identifying ground deformation patterns in coal mining areas using historical high-precision digital elevation models (DEMs), including data preprocessing, DEM subtraction operations, interpretation, and fitting correction. This method was applied to the Yulin National Energy and Chemical Base and successfully identified the ground deformation characteristics of the Yulin coal mining area from 2015 to 2019. By determining surface subsidence displacement, excavation depth, stacking height, and the position of the goaf suspended roof area, the objective situation of ground deformation in Yulin mining area was obtained, and the mining methods and distribution characteristics of different surface deformations were analyzed and determined. The research results are of great significance for the development of mineral resources in mining areas, reducing geological disaster risks, protecting the ecological environment, and achieving the goal of coordinated development in mining areas.

Development of novel tasar cultivation zones and conservation of vanya silkworms in ecologically-restored sites within degraded mined-out areas of Purnapani, Odisha

Aim: The aim was to develop tasar cultivation zones by introducing diverse tasar host plant species at mined out sites undergoing ecological restoration for generating sustainable livelihood option for local tribals. Methodology: The site selected for vanya sericulture was an integral part of ecologically restored 250 -acres limestone/dolomite mined out area of Steel Authority of India Limited (SAIL).Tasar cultivation zones were developed by planting saplings of host plant species viz, Terminalia tomentosa (Roxb.) ex DC., Terminalia arjuna Wright & Arn., Terminalia belerica (Gaertn) Roxb, Ziziphus mauritiana Lam., Terminalia chebula Retz. and Syzygium cumini (L.) Skeels. These cultivation zones are currently scattered among nine forest communities that were developed by growing saplings of more than 260 native species of trees and shrubs, besides ground vegetation, using ecosystem approach. Women self-help groups were formed and trained in rearing of tasar silkworms as well as making tasar-based products to ensure continuous practice of tasar silkworm culture at these novel cultivation zones. Results: During early ecological stages of ecosystem redevelopment through restoration of the habitat, it was observed that wild tasar moths laid eggs and silkworms spun cocoons, albeit in very small quantity, indicating suitability of foliage as food for larvae. In the year 2019-2020 alone, an estimated one lakh cocoons were produced from DFLs procured from CTRTI, Ranchi,and sent to the market/stored as seed cocoon. The average income per member of self-help group from sale of tasar cocoons was Rs 7, 855 (INR) annually. Interpretation: The restored ecosystems in the limestone/dolomite mined-out areas of SAIL at Purnapani serve as an excellent model for conservation of Tasar gene pools and sustainable livelihood development that can be replicated elsewhere. Hence, this practise can serve as an excellent model for replication elsewhere. Key words: Biodiversity, Ecological restoration, Livelihood, Mined out areas, Self-help group, Tasar silkworm