IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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Electrical resistivity tomography technique coupled withnumerical modelling: A case study for stability analysis
No full textCavity due to underground old mine workings is one of the major threats to the coalmines and the overlying subsurface and surface properties, which need to be protected. The detection of old mine workings and stability assessment of overlying strata are common problems in most of the Indian coalfields. Several coal mines in India are loss-making, mainly due to different types of mine hazards. Khandra mine is one such mi neat Raniganj Coalfield, Eastern Coalfields Ltd., a subsidiary of Coal India Limited. In the present study, 2-dimensional and 3-dimensional electrical resistivity tomography were carried out for detailed subsurface characterization. It supports delineating underground workings, including the nature of voids/cavities (air or water-filled). Excessive distor-tions were reported in electrical resistivity tomography application, especially at the near-surface, owing to large resistivity variations. Refinement of the model by half-unit electrode spacing was attempted here to reduce the distortions with minimum possible absolute errors. 3-Dimensional resistivity volumetric model was also developed with the help of five electrical resistivity tomography parallel profiles for better apprehen-sion of the subsurface. Analysis provided important inputs for stability analysis using3-dimensional numerical modelling. The physico-mechanical properties of the overly-ing strata, pre-excavation in situ stresses, boundary conditions and the mine geometry simulation were incorporated for understanding the stability analysis. Stability analysis was carried out using the finite difference technique. The analysis of 3-dimensionalnumerical modelling indicated that two distinct layers comprising (i) laterite/part of the course to medium-grained sandstone and (ii) developed galleries of R-IX seam exhibited a very low safety factor below 1.0, indicating potholing/subsidence susceptibility . The other three layers comprising parts of fine-grained sandstone exhibited a relatively higher safety factor of around 2.0, indicating moderately stable zones, but not on a long-term basis. Parts of Siduli stream embankments need suitable retaining walls to avoid water inundation for the stability of the area
The Longleaf Tree-Ring Network: Reviewing and expanding the utility of Pinus palustris Mill. Dendrochronological data
No full textThe longleaf pine (Pinus palustris Mill.) and related ecosystem is an icon of the southeastern United States (US). Once covering an estimated 37 million ha from Texas to Florida to Virginia, the near-extirpation of, and subsequent restoration efforts for, the species has been well-documented over the past ca. 100 years. Although longleaf pine is one of the longest-lived tree species in the southeastern US—with documented ages of over 400 years—its use has not been reviewed in the field of dendrochronology. In this paper, we review the utility of longleaf pine tree-ring data within the applications of four primary, topical research areas: climatology and paleoclimate reconstruction, fire history, ecology, and archeology/cultural studies. Further, we highlight knowledge gaps in these topical areas, for which we introduce the Longleaf Tree-Ring Network (LTRN). The overarching purpose of the LTRN is to coalesce partners and data to expand the scientific use of longleaf pine tree-ring data across the southeastern US. As a first example of LTRN analytics, we show that the development of seasonwood chronologies (earlywood width, latewood width, and total width) enhances the utility of longleaf pine tree-ring data, indicating the value of these seasonwood metrics for future studies. We find that at 21 sites distributed across the species’ range, latewood width chronologies outperform both their earlywood and total width counterparts in mean correlation coefficient (RBAR = 0.55, 0.46, 0.52, respectively). Strategic plans for increasing the utility of longleaf pine dendrochronology in the southeastern US include [1] saving remnant material (e.g., stumps, logs, and building construction timbers) from decay, extraction, and fire consumption to help extend tree-ring records, and [2] developing new chronologies in LTRN spatial gaps to facilitate broad-scale analyses of longleaf pine ecosystems within the context of the topical groups presented
Design of Stable Parallelepiped Coal Pillars Considering Geotechnical Uncertainties
No full textThe stability of underground parallelepiped coal pillars formed during trunk road development in inclined coal seams is very important for safe access to the mine workings. These protective coal pillars developed around the trunk roads have the longest life span in coal mines. Although these pillars are designed with high safety factors, their failures continue to occur especially in inclined coal mines. The acute corners of parallelepiped coal pillars are highly stressed and prone to failure. These failures may be attributed to the deterministic safety factor which does not consider field geotechnical uncertainties in their design parameters. This research work identified the geotechnical uncertainties in pillar designs and incorporated them in designing stable pillars in inclined coal seams. A probabilistic approach based on limit state function has been proposed for designing stable parallelepiped coal pillars and validated in an inclined coal mine. In this study, the working stresses of the inclined coal pillars are varied for evaluating their influence on pillar reliability using the three cases of the limit state functions namely, empirical, numerical average, and numerical maximum. The pillar reliabilities were estimated by Monte Carlo Simulation. The results indicate that the empirical and numerical average cases yielded stable pillars, whereas the numerical maximum case provided an unstable design. The correlation between safety factor and reliability has been established which can predict the reliability for a given safety factor of pillars with a similar range of design inputs. Further, the threshold values of pillar sizes, acute corner angles, and seam gradients for the reliable pillar design have been determined by sensitivity analysis. These findings can help in designing stable parallelopiped pillars, especially in inclined coal seams to reduce pillar failures and enhance mine safety
Evaluation of a novel pyramidal design of rock bolt bearing plate using analytical, experimental, and numerical methods
No full textGround failures in underground mines are continuing to occur despite using rock bolt support with higher anchorage. The reason may be attributed to the mismatch between bolt anchorage and bearing plate capacity. Currently, the dome-bearing plates are widely used in the reinforcement of ground which often fails at loads below the bolt anchorage capacity. To address this problem, a novel pyramidal design of a bearing plate is proposed keeping the same size and material properties as the conventional dome plate. To evaluate the performance of pyramidal design, analytical formulations of load resistance, load efficiency, and energy absorption are formulated. In the experimental study, the prototypes of pyramidal design are developed and subjected to compression tests along with the conventional dome plate. The calibrated model of tested bearing plates is simulated using 3-dimensional finite element analysis. The pyramidal plate outperforms the dome plate in performance evaluation in terms of load resistance, load efficiency, and energy absorption. The experimental and numerical results also indicated that the capacity of the pyramidal plate is superior to that of a conventional dome plate. Thus, the proposed pyramidal plate can be used with rock bolt support in underground openings for improved ground control and stability
Soil pollution in Indian coal mines, available remediation techniques and rock dust application: A review.
No full textSoil pollution due to coal mining and its associative activities has become a serious environmental concern in India. The by-products of coal mining are often disposed directly to the bare lands, significantly altering the characteristics of soil up to a considerable extent. These stacks of discarded rock wastes under the influence of various geological agents, viz., wind, running water, etc., undergo leaching and release trace metals into the soil. Consequently, different environmental, geomorphological, and health problems arise. Various remediation techniques are available for soil pollution, which are classified as conventional techniques like soil replacement, thermal desorption, chemical leaching and fixation, etc. and biological techniques, which are bioremediation and phytoremediation. However, the commercial application of these remediation techniques has not gained popularity due to inefficient technologies, unawareness and costlier methods. Recently application of rock dust has emerged as a potential tool for remediating and remineralising the mine soils along with the management of discarded solid waste rocks. This review details the deteriorating effects of coal mining and allied activities, especially in the case of open cast mining, on the physical, chemical and biological characteristics of soil, discusses the different techniques available for remediation of contaminated soil, and how rock dust can be gainfully applied for soil remediation and remineralisation in India and worldwide. Research gaps and conflicts in the utilisation of rock dust have also been presented
An overview on remediation technologies for polycyclic aromatic hydrocarbons in contaminated lands: a critical approach
No full textPolycyclic aromatic hydrocarbons (PAHs) are bonded organic compounds with numerous structures with different toxicity levels. They can be of low molecular weight with 2–3 rings or high molecular weight with more than four rings and are persistent in nature. They possess high molecular weight and boiling point, hydrophobic with minimal solubility in water, and lipophilic with high solubility in organic solvents. With the gain in molecular weight, their susceptibility to oxidation–reduction decreases. They are generated during incomplete combustion of organic materials. They can be natural, such as forest fires, or artificial agents, such as coal, oil, wood burning, smoke, and auto-emissions. Due to strong molecular bonds and structural complexity, PAHs are highly malignant under normal conditions. They cause environmental damage due to improper handling and disposal in the surrounding air, water, soil, etc. PAH contamination is highly toxic because of mutagenic and potentially immune toxicants, often resulting in higher workplace casualties. Various physical, biological, and chemical processes remediate the PAHs in contaminated land. Indigenous microbial communities can effectively degrade it in-situ or ex-situ conditions. The degradation process depends on the type of microorganism, its life cycle, PAH substrate, pH, temperature, pressure, and the reaction mechanism. The present article discusses current literature, chemistry, natural and anthropogenic sources of generation, impacts on the environment, biota, etc., merits of physical, biological, and chemical remediation mechanisms with emphasis on microbial degradation, and novel options of technology intermix suitable for sustainable remediation outcomes
Tensile strength of cemented paste backfill for lead–zinc mill tailings: lab and in situ scenarios
No full textCemented paste backfilling (CPB) in underground mines is a widely accepted backfilling technique. It has plenty of scope for application in Indian underground mines. Both the uniaxial compressive strength (UCS) and tensile strength (TS) are the essential CPB design parameters. During adjacent stope extraction, minor principal stresses in the backfill mass increase; to overcome these minor principal stresses, the CPB should have sufficient TS. There are limited studies reported in literature about TS of CPB both in lab and in situ conditions, correlation between TS and UCS of CPB and tensile strength prediction models. In this article, the tensile strength development in CPB prepared using lead–zinc mill tailings with different binders (cement, fly ash, and slag) was investigated and statistical tensile strength prediction models were developed. Moreover, the correlation between TS and UCS of CPB was statistically determined with a developed correlation model. Further, the in situ strength of paste backfill specimens was determined and compared with the lab-determined strength. The in situ backfill specimens showed a shrunk of 28-day UCS and TS by 9% and 7%, respectively, as compared to lab-prepared specimens. The findings of this study would help in bulk environment-friendly tailings disposal in underground mines, better backfill strength design, and further excavation processes in lead–zinc underground mines
Mercury in coal from south eastern coalfeld and mercury partitioning at sub‑critical coal‑fred power plant
No full textIndia is considered as one of the major mercury emitters of the world. Coal combustion in power plants is the foremost source of mercury emissions. Coal samples from South Eastern Coalfeld (SECL) region, India were assessed for mercury content and its partition in a 500 MW boiler unit of a coal-fred power plant. Hg content in the runof mine coal samples varied from 0.011 to 0.188 mg/kg. The Hg content in coal was positively correlated with ash and sulfur. In the power plant, about 65% of the Hg present in the feed coal was emitted through stack, whereas the rest were associated with the fne fy ash (33%), bottom ash (1.9%), and mill rejects (0.1%).The concentration of total Hg in the stack gas varied from 8.5 to 13.7 μg/Nm3, wherein Hg0 (74–81%) was much higher than Hg2+ (19–26%). The estimated mercury emission factor was 1.0–3.2 mg/GJ, which is comparatively higher due to the use of high ash coal and the lack of fue gas desulphurisation system. Hg portion�ing along the fue gas hoppers were also investigated which indicates relationship between Hg adsorption and carbon/sulfur
content of the fy ash
Exploring the potential of sulphur forms in Northeastern Indian coals: Implications in environmental remediation and heavy metal sensing
No full textThe Sampar Coalfield in Northeastern India is a source of plentiful coal reserves, which are burnt for energy production and industrial applications, resulting in the release of pollutants such as sulphur , arsenic, and lead, which are hazardous to the environment and public health. In this work, samples from the Sampar coalfield have been analyzed to understand the origin, distribution, and various forms of sulphur and their ability to detect toxic heavy metals. The total sulphur concentration ranged from 4.31% to 6%, with organic sulphur being the predominant form at 69.21%, followed by pyritic sulphur at 16.49% and sulphate sulphur at 14.28%. With high sulphur content, this coal indicates a marine influence in the peat-forming swamps. The samples have also been examined for petrographic and elemental analysis, which have revealed the presence of vitrinite, liptinite, inertinite, carbon, hydrogen, nitrogen, oxygen, and mineral matter. In addition, the same coal sample has also been used for electrochemical sensing-based detection of toxic heavy metals like arsenic and lead, and the findings indicate an improved efficacy. These results are expected to have significant implications in the development of effective bio-based remediation strategies in the region to mitigate the harmful effects of coal-related pollution
Human Health Risks due to Exposure to Water Pollution: A Review
No full textWater resources are crucial in developing any area as they serve as a major source of potable, agricultural, and industrial water. Water contamination, caused by natural and anthropogenic activities, poses a significant threat to public health globally. This review synthesizes data from various studies published in national and international journals, as well as reports from governmental and non-governmental organizations. Our primary objective is to understand and review previous research on water pollution, contamination types, and the effects of water contamination on public health. Water pollution studies generally involve a scientific understanding of the biological, chemical, and physical processes that control the movement of contaminants in the underground environment. The nature and severity of health consequences vary based on several factors, including the chemical composition, duration of exposure, and concentration of pollutants. This work highlights the human health risks associated with current research topics such as anthropogenic, geogenic, microplastics, pharmaceuticals, and heavy metals. A section on remedial measures and mitigation strategies is included to emphasize sustainable approaches to water conservation, replenishment, and sustainability. However, there is a lack of comprehensive knowledge regarding the distribution, toxic effects, and human health risks associated with different sources of contamination. This review thus establishes links between multiple sources of pollution, their toxicity to human health, and approaches to health risk assessment