Mine Voids Research Articles

Utilization Study of Void Mine For Sustainable Environment of The Limestone Mining Sector at PT Semen Baturaja (Persero) Tbk

Event open-pit mining methods in the exploitation of limestone by PT Semen Baturaja (Persero) Tbk cause depletion of water, air, and soil. At the end of mining activities will leave ex-mine land in the form of void and non void (empty land). Reclamation and Postmining must be carried out by the company according to the mandate of Government Regulation No. 78 year 2010. Reclamation and post-harvest activities on ex-non void mines can be revegetation activities, while void can be used as reservoirs for raw water sources. The aim is to maintain the sustainability of natural resources and water in the limestone mining environment. The research aims to determine the condition of void water produced from limestone mining activities for a sustainable environment. The method used in this study is using the pollution index method. The results showed that the water in the sump inlet and quarry outlet experienced mild pollution. Pollution index at the location of the limestone mine sump inlet worth 2.14 and for oulet quarry worth 2.07. This shows that mine void water is not feasible to be used as raw water, so water treatment needs to be done so that it meets the established quality standards. If void water comply the prescribed quality standards, environmental sustainability in the limestone mining sector can be achieved during during the life of the mine, post mining, until after the post-mining period.

A Study of the Stress State of Underground Gas Pipelines in Mine Working Zones Using the Method of Internal Response Function

The stress state of pipelines in mine working zones, where the main loading factor is longitudinal soil displacements caused by the gradual filling of mine voids, has been calculated. Differential equations of pipe deformation have been formulated, for the solution of which the method of internal response function is proposed, which takes into account the mutual displacement of the pipe and soil in each iteration using a classical three-part nonlinear model of pipe–soil interaction. The type of interaction is determined on the basis of the concept of the basic displacement of the pipe, which is refined using displacements calculated in the previous iteration. The procedure of refining the basic solution is an important component of the method, where the basic solution in the next iteration is found as the sum of the previous solution and the difference between the calculated and previous solutions, multiplied by the convergence-control factor of the iterative procedure. To check the convergence accuracy and rate of the proposed iterative procedure, a comparative analysis with other existing procedures and results, obtained with the aid of commercial finite element programs, has been performed. To diagnose the stress state of pipelines during the working of longwall faces, a system for their continuous monitoring has been created. The correctness of the results of the performed numerical modeling of the stress state of a gas pipeline and the effectiveness of the measures that are developed to reduce the high stress level in its individual zones have been confirmed by relevant monitoring data, which are important both for refining the physical characteristics of pipe–soil interaction and for further taking into account the relaxation of these relations in time.

Mathematical Model of Benefits and Costs of Coal Mining Environmental

Environmental sustainability is a key issue of the coal mining sector. This is because the impact of damages on activities undertaken in this sector is deemed vulnerable to environmental sustainability. The damage that occurs has an impact on environmental unsustainability. The value of environmental sustainability is set forth in the Government Regulation No. 46 of 2017 on Environmental Economic Instruments. Under this regulation, any activity that has an impact on the environment including the coal mining sector shall assess the damage it causes. The mathematical model of environmental benefits and cost of coal mining discovered by Juniah (2013), is an expansion of the extended mathematical model of the benefits and costs of Munasinghe (1997). This model can be used and implemented to assess environmental losses and determine the value of environmental sustainability of coal mining as intended by the Government Regulation of the Republic of Indonesia. The environmental losses can be minimized by utilizing water void mine as raw water. This model can also be used by government, stakeholders, and mining investors to assess the sustainability of the coal mining environment for the resulting externalities, and the utilization of mine void water as raw water.

Long-term leaching assessment of constituent elements from Linz–Donawitz slag of major steel industries in India

Continuous long-term open column (> 1 year, during July 2014–July 2015) percolation leaching experiments were undertaken to assess leachability of important constituent elements from Linz–Donawitz slag of Rourkela, Bokaro and Tata steel plants. Leachates were continuously collected at an interval of 3–5 days from open column during 110 cycles of percolation leaching test and analysed for As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Se, V and Zn concentration by inductively coupled plasma optical emission spectrometry. Leachate concentration of different elements showed remarkable variation in terms of leachability from different slag samples. Linz–Donawitz slags cumulative concentration of the elements in the leachate (µg/kg) range showed Mn (16.13–57.73) > Fe (38.36–54.43) > As (8.06–19.66) > Cu (7.83–10.66) > Cr (5.2–6.53) > Ni (5.2–6.16) > Zn (BDL—5.76) > Se (BDL—5) > Co (BDL—3.66) decreasing trend. Among Linz–Donawitz slags, Cr, Ni, Se and Zn leachate concentrations were relatively higher for Tata, whereas As, Co and Fe were higher for Bokaro. Leachate concentration of Cd, V and Pb was below detection limit in all slag samples from the steel plants. During initial period of leaching experiments, concentration of many elements (As, Cu, Fe and Mn) showed increasing trend, which reaches a plateau afterwards. The experimental results estimate low cumulative leachate content of different elements from Linz–Donawitz slag and therefore has prospect for bulk utilization for reclamation of degraded land, mine void filling, road construction etc.

Detection of Cavity Using Electrical Resistivity Tomography (ERT) at Patherdih, Jharia Coal Field, Dhanbad, India

Geophysical survey for cavity detection is one of the most common near surface application. The usage of resistivity methods are also very straightforward for the air filled underground voids, which should have theoretically very high resistivity in the ERT image, whereas the water filled cavities have low resistivity in Electrical Resistivity Tomography (ERT) image. Three different geoelectric arrays Wenner, Schlumberger and Dipole-dipole are applied for detecting cavities. The survey results suggest that ERT is a viable geophysical tool for the detection and monitoring of mining voids and other subsurface cavities. The resolution capacity of joint Wenner-Schlumberger, Dipole-dipole array for the detection of cavity is greater than that of the individual one. Using the ERT survey in Patherdih Thana Basti village (Jharia coal field), a number of air filled cavity or water filled mining voids are detected at around 25-30m of below the ground level at different profile distance of 630m profile length along the road that extending S-E to N-W direction.

Design of underground mine voids filling operations in difficult flow conditions of fly ash – water mixtures

Filling the underground voids created during mining extraction of minerals plays a crucial role in different phases of mining operations. A common practice in Polish coal mines is filling the cavings resulted from coal extraction in longwalls for various safety and technical purposes. Moreover, liquidation of redundant underground workings and decommissioning of mines also require filling of large volumes of voids. As the obsolete mining systems with hydraulic backfill have been entirely replaced by longwalls with caving, a need arose for flexible and easily available method for filing of voids. Nowadays, the most frequently applied are mixtures of fly ash and water, which are able to meet a wide range of requirements of specific applications. These objectives may be achieved by the selection of the type of fly ash and adjustment of concentration of solid in mixture in the respect to geometrical parameters of the transport pipeline. These correlations have been demonstrated on the example of measurements conducted on a laboratory pipeline loop for a wide range of fly ash – water mixtures and flow conditions. Measurement results revealed a complex relationship between rheological properties of mixtures and geometrical parameters of pipelines, which strongly influence the distance at which a mixture may be delivered.

SIMPL: A Simplified Model-Based Program for the Analysis and Visualization of Groundwater Rebound in Abandoned Mines to Prevent Contamination of Water and Soils by Acid Mine Drainage.

Cessation of dewatering following underground mine closure typically results in groundwater rebound, because mine voids and surrounding strata undergo flooding up to the levels of the decant points, such as shafts and drifts. SIMPL (Simplified groundwater program In Mine workings using the Pipe equation and Lumped parameter model), a simplified lumped parameter model-based program for predicting groundwater levels in abandoned mines, is presented herein. The program comprises a simulation engine module, 3D visualization module, and graphical user interface, which aids data processing, analysis, and visualization of results. The 3D viewer facilitates effective visualization of the predicted groundwater level rebound phenomenon together with a topographic map, mine drift, goaf, and geological properties from borehole data. SIMPL is applied to data from the Dongwon coal mine and Dalsung copper mine in Korea, with strong similarities in simulated and observed results. By considering mine workings and interpond connections, SIMPL can thus be used to effectively analyze and visualize groundwater rebound. In addition, the predictions by SIMPL can be utilized to prevent the surrounding environment (water and soil) from being polluted by acid mine drainage.

Storing energy in disused underground mine voids: comparing pumped water- and compressed air-based technologies

Large scale energy storage is becoming ever more important for balancing loads due to increased intermittent electric energy supply from wind and solar power plants. This paper explores how abandoned mine voids can be utilised for this purpose comparing the technological and economical suitability of two different technologies: underground pumped hydro energy storage (UPHES) and compressed air energy storage (CAES). By integrating these technologies into post-closure development concepts mine voids can be prevented from becoming environmental liabilities thereby averting costs associated with the indefinite pumping and treating of polluted water emanating from flooded mines. Apart from differing in construction costs, profitability, energy storage capabilities and grid-related flexibility each technology also requires different geological conditions that are to be considered when selecting the best suited one for a specific mine.

Storing energy in disused underground mine voids: comparing pumped water- and compressed air-based technologies

Storing energy in disused underground mine voids: comparing pumped water- and compressed air-based technologies

Is the long-term sequestration of CO2 in and around deep, abandoned coal mines feasible?

Many of the largest fixed sources of CO2 emissions are major power stations located on or very close to major coalfields. Even when local coal reserves are exhausted, coal- and/or biomass-fired power generation often persists at such sites, as they occupy pivotal positions in the national power grids that developed around them. To date, strategies for CO2 sequestration from such power plants have focused on long-distance transport by pipeline to depleted hydrocarbon reservoirs and similar deep saline aquifers. Yet where abandoned coal mines extend more than about 800 m below ground level, the void space represented by the old mine voids themselves, and roof strata that have been rendered more permeable by void collapse, could represent convenient auxiliary loci for CO2 sequestration. Furthermore, the geochemical nature of coal and coal-bearing strata may offer mechanisms for entrapment of injected CO2 in or on the solid phase that are not available in potential storage zones considered to date. Engineering evaluation of this possibility requires consideration of the likely fate of CO2 in free, adsorbed, dissolved, and mineralized forms, and of the geotechnical integrity of enclosing strata and abandoned mine infrastructure that could serve as seals to trap injected CO2 in place. A protocol for assessing these factors has been developed, based on critical evaluation of mining records, hydrogeological conditions, and geotechnical data, resulting in a quantitative assessment of the capacity for CO2 sequestration represented by deep abandoned coal mine workings. Preliminary application of the decision logic is illustrated for the Daning coal mines in China.

Application of mine water leaching protocol on coal fly ash to assess leaching characteristics for suitability as a mine backfill material

ABSTRACTOver the years, coal mining in the Mpumalanga Province of South Africa has negatively affected the environment by causing pollution of water resources, land subsidence and spontaneous coal combustion. Previous studies show that in-situ treatment of acid mine drainage (AMD) using coal fly ash (CFA) from local power stations was possible and sludge recovered out of such treatment can be used to backfill mines. In this article, the authors have attempted to understand the leaching characteristics of CFA when placed underground as a backfill material using the mine water leaching protocol (MWLP). The results show that the migration of contaminants between the coal fly ash and the AMD in the mine voids depends on the pH and quality of the mine water. While backfilling mine voids with CFA can neutralize and scavenge between 50% and 95% of certain environmentally sensitive elements from AMD such as Fe, Al, Zn, Cu, Ni, Co and Mn. At this moment, it is also important to point out that certain scavenged/removed contaminants from the AMD during initial phases of backfilling can be remobilized by the influx of acidic water into the mine voids. It has therefore been concluded that, while CFA can be used to backfill mine voids, the influx of fresh acidic mine water should be avoided to minimize the remobilization of trapped contaminants such as Fe, Al, Mn and As. However, the pozzolanic material resulting from the CFA-AMD interaction could prevent such influx.

Analysis and Prediction of Gas Recovery from Abandoned Underground Coal Mines in China

Abstract Mine closures are likely to become especially widespread in eastern China. However, because of relatively high residual coal-bed methane content, the abandoned coal mine methane (ACMM) reserves of China are huge, and from a greenhouse gas–control perspective it is preferable that they be developed and utilized rather than allowed to vent to the atmosphere. The exploitation and development of ACMM in China is still in its infancy, with theory and practice undergoing rapid development. Four factors are particularly influential in the design of ACMM recovery strategies. The first factor is what may be termed the “enrichment space,” which reflects the final state of the strata after completion of longwall extraction and subsequent strata settlement and is here defined as the region between the outer limit of stress relief and the limit of the extracted panels. Quantitative analysis of the components of gas mixtures recovered from the enrichment space can be tracked using stable carbon isotope techniques. The second factor is the permeability field surrounding the abandoned mine voids. The thick mudstones that commonly overlie the coal seams serve to confine the water and gas within the enrichment space and old mine voids. The geometry of these confining layers can be confirmed by seismic reflection or other geophysical methods, which can reveal the extent of the zone affected by fracture development. On this basis, models of methane movement in abandoned mines can be constrained, allowing valuable predictions of availability of ACMM resources under different mining and post-closure drainage conditions.

Measurements of evaporation from a mine void lake and testing of modelling approaches

Pit lakes often form in the void that remains after open cut mining operations cease. As pit lakes fill, hydrological and geochemical processes interact and these need to be understood for appropriate management actions to be implemented. Evaporation is important in the evolution of pit lakes as it acts to concentrate various constituents, controls water level and changes the thermal characteristics of the water body. Despite its importance, evaporation from pit lakes is poorly understood. To address this, we used an automated floating evaporation pan and undertook measurements at a pit lake over a 12 month period. We also developed a new procedure for correcting floating pan evaporation estimates to lake evaporation estimates based on surface temperature differences. Total annual evaporation was 2690 mm and reflected the strong radiation inputs, high temperatures and low humidity experienced in this region. Measurements were used to test the performance of evaporation estimates derived using both pan coefficient and aerodynamic modelling techniques. Daily and monthly evaporation estimates were poorly reproduced using pan coefficient techniques and their use is not recommended for such environments. Aerodynamic modelling was undertaken using a range of input datasets that may be available to those who manage pit lake systems. Excellent model performance was achieved using over-water or local over-land meteorological observations, particularly when the sheltering effects of the pit were considered. Model performance was reduced when off-site data were utilised and differences between local and off-site vapor pressure and wind speed were found to be the major cause.

Land subsidence inversion method application for salt mining-induced rock mass movement

AbstractThe modeling of strains and deformations in salt mine areas encounters considerable difficulties because of the varying strength properties of salt, the complex morphological build of dome deposits and the rheological properties of salt. These properties have impacted the development of salt extraction for hundreds of years and the fact that the accurate determining of strains in a given specified moment and place are burdened with high uncertainty. Numerical modeling is useful when the model is reduced to one or several salt chambers. A broader range of underground post mining void considerably lowers the accuracy and efficiency of the calculations of such models. Stochastic models allow for a 3D modeling of the entire mining complex deposit, provided the model has been parametrized in detail. The methods of strains and deformations modeling were presented on the example of one of the biggest salt mines in Europe, where a volume of over 21 million m3 of salt was extracted. The stochastic model could be parametrized thanks to the documented results of measurements of convergence of the underground mining panels and leveling on the surface. The use of land subsidence inversion in the least squares method allowed for estimating the optimum values of parameters of the model. Ground deformation modeling was performed using the two-parameter time function, which allows for a simulation to be carried out in time. In the simulation, the convergence of underground excavations and the transition in time the effects of convergence into ground subsidence was taken into account. The detailed analysis of the geological conditions lead to modeling deviation of the subsidence trough. The accuracy of the modeling results was qualitatively and quantitatively confirmed by a comparison of the modeled to measured values of the vertical ground movement. The scaled model can be applied in future mining extraction projects in order to predict the strains and deformations for an arbitrary moment in time.

FLY ASH MIXING WITH MINE OB DUMPS: AN ENVIRO-FRIENDLY, CLEAN AND GREEN METHOD OF DISPOSAL

Fly ash generation, its utilization and safe disposal is a major problem faced by thermal power plants (TPP) in India. Despite several efforts of the government, the utilization of fly ash is reached to only 55% of the total fly ash generated and remaining 45% fly ash is still being dumped into poorly designed and maintained ash ponds. At present, fly ash is mainly being utilized for making cement, bricks, concrete, roads and small quantity in mine void filling. The consumption of fly ash in construction activity has reached to almost saturation level and there is not much potential to consume more fly ash in these segments. Mine void filling is the only potential area where bulk quantity of fly ash can be utilized and 100% utilization target can be achieved. This paper investigates the suitability of fly ash to be disposed off by mixing it with overburden (OB) dumps in coal mines. Characterization of both the OB dump material and fly ash were carried out in the laboratory. The compaction and shear tests were performed on OB dump material and the same mixed with 25% fly ash by volume as per the guidelines issued by Ministry of Environment Forest and Climate Change, Govt. of India. The stability condition of both OB dump and fly ash mixed OB dump at varying slope angles were analyzed using FLAC 3D slope stability software and dump angle were optimized for safe disposal of the fly ash. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.105121 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Cradle to cradle solution to problematic waste materials from mine and coal power station: Acid mine drainage, coal fly ash and carbon dioxide

During mining, minerals such as FeS2 are exposed to O2, H2O, and microorganisms resulting in the oxidation and generation of acidic water. The acidic water causes chemical weathering of the adjacent rocks and leaching of potentially toxic metals and the resultant water is often termed acid mine drainage (AMD). Coal power stations produce an alkaline aluminosilicate waste material called fly ash (CFA). Modern waste resource management emphasises finding useful applications of waste generated from processes to achieve a green economy. CFA was, with additional lime and Al(OH)3 used to treat AMD at a 80L pilot scale. Most of the physical and chemical parameters of the treated water were within South African target water quality range (TWQR) for irrigation. Carbonation of the water after treatment with CFA, lime and Al(OH)3 produced water that was within the TWQR for irrigation with respect to all parameters and resulted in the sequestration of 15–123L of CO2 per 80 L of AMD treated at standard ambient temperature and pressure. CO2 reacted with Ca ions in the water and solid residues to form CaCO3. Carbonation improves the ease of disposal of CFA, the AMD quality as well as reducing the amount of CO2 emissions by coal power plants through mineral carbonation. The solid residues from the overall process are suitable for the back filling of mine voids thereby preventing AMD generation by excluding air and water. This is an innovative cradle to cradle solution for the disposal of waste materials from coal mines and power stations.

The rock pillar stress analysis in order to obtain an effective dimensioning and guarantee the mining void stability

In the room and pillar mining method is of fundamental importance the dimensioning of the pillars. The area of influence method is typically used today for dimensioning of the pillars, but an overdimensioning or critical stability conditions can happen with this method. A parametric analysis with tri-dimensional numerical modelling was carried out to study in the detail the stress conditions in the rock pillars. This made it possible to identify a critical point, where the minimum local safety factor is reached, at the corners of the pillar close to the roof of the mining room. Through the estimation of the major principal stress at the critical point it was possible to evaluate the minimum local safety factor in function of the geometric and geomechanical parameters of the problem. The dimensioning of the pillars through the local safety factor at the critical point makes it possible to avoid overdimensioning and static problems, which instead can occur when simplified calculation methods are used. The use of proposed figures can allow a fast pre-dimensioning of the pillar, leaving the more detailed numerical modelling only to the found geometric configuration.

Evaluation of analytical models for heat transfer in mine tunnels

The heat contained in underground flooded mine workings is actively exploited, often via heat pump technology, at a number of locations in Europe and North America. Several different heat exchange configurations may be utilised in this context, but for those (“standing column” and “open loop” arrangements) were mine water reinjection is practised, the rate of heat transfer between mine walls and mine water is a critical process to quantify. The two most commonly-used analytical solutions to this problem have been applied to the same baseline scenario, exploring and comparing their sensitivity, strengths, weaknesses and areas of application. It is found that the Rodríguez- Díaz solution generally predicts heat transfer rates (typically of the order of several tens of W per m of tunnel) greater than the Lauwerier-Pruess-Bodvarsson approach, the difference being due to the fact that the former assumes a radial heat conductive flow geometry in the rock surrounding the mine void, while the latter assumes a less efficient parallel linear flow. The Rodríguez-Díaz solution is more appropriate for approximately cylindrical mine shafts and tunnels. The Lauwerier-Pruess-Bodvarsson approach is more likely to be applicable to tabular mined void geometries. Improvements to the Rodríguez and Díaz model are proposed to enhance its transparency and applicability.

Characteristics of Microbial Coalbed Gas during Production; Example from Pennsylvanian Coals in Indiana, USA

Coalbed gases from 11 wells producing from the Springfield and Seelyville Coal Members (Pennsylvanian) were analyzed for composition and carbon and hydrogen stable isotope ratios in four sampling events to investigate short-term variation trends. Nine wells in the Seelyville Coal Member produce coalbed gases from the virgin seam, whereas two wells in the Springfield Coal Member produce gas from mine voids. Methane dominates gas composition in all wells, and its content ranges from ~94% to almost 98%, with ethane typically accounting for less than 0.01%. Carbon dioxide content in most samples is below 1%, whereas N2 content ranges from less than 2% to 4.8%. Methane δ13C values range from −55.3‰ to −61.1‰, and δ2H values range from −201‰ to −219‰. Isotopic values of methane and C1/(C2 + C3) ratios indicate a biogenic origin along the CO2-reduction pathway, consistent with previous studies in this area. Our results demonstrate that gas properties may change significantly during a period of one year of production history. Compositional trends (e.g., C1/(C2 + C3), CH4/CO2 ratios) are specific for each well and often irregular. These changes result from a combined influence of numerous factors and, therefore, are difficult to predict.

An Analytical Solution of Gibson’s Model for Estimating the Pore Water Pressures in Accreting Deposition of Slurried Material Under One-Dimensional Self-Weight Consolidation. Part I: Pervious Base

Every year, mines produce a large amount of tailings that must properly be managed. For most cases, the tailings are sent by pipes and disposed of in tailings dams. Another more and more common practice is to send a part of the tailings with or without cement binder to underground to fill mine voids (stopes). In civil engineering, a similar practice is the deposition of dredged sludge pumped and confined in a containment structure (dam for most cases). In these cases, an important challenge is to determine the pore water pressure (PWP) associated with the self-weight consolidation of the slurried backfill disposed layer by layer. A solution to the self-weight consolidation of accreting (increase in thickness) deposition of slurried material was first proposed by Gibson in late 1950s. Recently, it has been revisited and applied to mine stopes backfilled with slurried materials. The solution can only be evaluated numerically. In this paper, a truly analytical solution is proposed that is based on the Gibson approach and can be readily used to manually calculate the variation and evolution of the PWP within accreting deposition. The effect of the filling rate, fill height and backfill properties on the variation and evolution of the PWP is analyzed. The solution is proposed for accreting deposition of slurried backfill placed on pervious base. An analytical solution for estimating the PWP within slurried backfill disposed on impervious base is presented in a companion paper.