The longwall mining is considered to be the best coal mining practices due to vast recovery of coal over other forms of underground as well as opencast mining methods. But the actual scenario is ...quite opposite in India where productivity form of the longwall mines lags far behind than the desired level. Irregular caving and sudden rock bursts, which are very hazardous for mine workers and equipment. Usually these are major problem faced by bulk of Indian longwall faces and which are due to the presence of thick sandstone beds as overlying strata. Thus to keep an eye on the rock bursts, it is very necessary to monitor the stressed zones in the hanging overlying strata above and behind the panel. Earlier Correlation Integral ‘C’ and Correlation Fractal Dimension ‘Dc’ has been very helpful in monitoring the stressed zones for several great earthquakes in past. Following the same way, in the present study we have used the mine-induced microseismic data obtained from the retreating longwall panel using various monitoring instruments to calculate the Correlation Fractal Dimension ‘Dc’ for monitoring the stress levels and fractures in the overlying strata and also for spatio-temporal forecasting of roof-falls. The variation of blast charge size with Fractal Dimension is also studied. The use of Fractal Dimension has been very effective in obtaining the precursory signatures for roof-fall, thus ensuring safety in the mines.
•Identification of stressed zones using Fractal signatures.•Prediction of roof-fall both within and behind the panel.•Spatio-temporal forecasting of roof-fall using Fractal Dimension.•Estimation of blast charge size using Fractal Dimension.•Fracture monitoring in the overlying strata.
Green and climate-smart mining (GCSM) can transform the traditional mining system into a more sustainable pattern by conserving the environment, reducing the ecological footprint, and promoting ...cleaner mineral production. Being a burgeoning concept, GCSM needs to be clearly defined and adequately understood to make it happen on a strategic scale. This study is an effort to propose an indicator framework for analyzing and prioritizing the identified indicators in order to render technical assistance for the implementation of GCSM. The proposed framework contains twenty-five sub-indicators categorized into six leading indicators (environmental protection, pollution control, waste management, energy and resource consumption, technology enablement and implementation, and strategic and managerial efficiency). The case of Chinese open-pit mines is presented to analyze the framework from two main aspects: the current situation of GCSM indicators (reality) and their significance in the development of GCSM (desirability). An integrated methodological approach involving the fuzzy analytic hierarchy process and grey clustering is applied, which first weighs each indicator and then further analyzes the level of greenness and climate-smartness (GCS) for each indicator. The findings reveal that all leading indicators fall into the “low” and “high” GCS levels in terms of reality and desirability, respectively. It indicates a negative tendency of GCSM performance and implies that if the efficiency of these indicators is improved, the GCSM performance in the future can be optimistic. This study enriches the existing literature, sets the stage for further research, and provides exploratory insights for an in-depth understanding of GCSM.
•Green and climate-smart mining positively influence the mining industry.•This study proposes an indicator framework and prioritizes identified indicators.•Twenty-five sub-indicators categorized under six leading indicators were finalized.•An integrated methodological approach is applied to the case study in China.•The analysis guides to render technical assistance for the domestication of GCSM.
Deep mining roadways are often under high-stress conditions and strong mining-induced disturbances. In the traditional longwall mining method, stress concentration and energy accumulation take place ...in the surrounding rock of the roadway, often causing dynamic disasters. To this end, the roof-cutting and energy-absorbing (RCEA) control method is proposed. Directional roof presplitting is used to transfer the roof stress and release the energy accumulated in the rock. Importantly, a roadway is automatically formed and coal pillars are eliminated. Moreover, new constant resistance energy-absorbing bolt and cable with high prestress and high elongation are used to control the roadway roof, which are independently developed. As a result, the self-supporting capacity of the rock is improved, and the energy released by the rock deformation is effectively absorbed by the support system. To verify the fidelity of the RCEA method, the numerical comparison test between the automatically formed roadway (AFR) method and the gob side entry driving method is carried out. Compared with the latter, the energy per unit length of AFR is reduced by 4.59*106 J, and the maximum energy density is reduced by 36.6%, which shows that AFR has profound effect on the energy release. Subsequently, the mechanical tests on the new bolt (cable) are carried out. The forces at fracture of the new bolt and cable are 1.63 times and 2.80 times that of the common bolt, and the maximum energy absorbed per unit length are 3.05 times and 2.89 times that of the common bolt. The new bolt (cable) has characteristics of high strength and high energy absorption. Finally, the strength-energy combined support design method and the field application are carried out. Field monitoring results show that the RCEA method can effectively release the energy accumulated in the rock and ensure the safety and stability of the roadway.
Challenging Canada's image as a humane, enlightened global actor, Colonial Extractions examines the troubling racial logic that underpins Canadian mining operations in several African countries.
Both coal and uranium resources are found in the Dongsheng area which is located in the northern part of Ordos Basin, China with the coal seam below the uranium deposit. In this paper, we attempt to ...study the feasibility of co-exploitation of the coal seam and the uranium deposit. The permeability evolution in strata around the coal seam are selected as the key parameter indexing the separate and safe concurrent recovery of two deposits and a novel strain-dependent permeability model is proposed covering the full deformation range of rock. The proposed model is first verified with experimental data with good fitting of the results. Then an upscaled numerical model is established considering the geology conditions of Dongsheng area. This is implemented using COMSOL Multiphysics; and the interface of COMSOL with MATLAB is used to study the damage to the rock mass. We show that (a) compared with the stress-dependent permeability model, the strain-dependent permeability model proposed in this work has the advantage that each strain value is associated with a unique permeability value; (b) The feasibility of co-exploitation of the coal seam and the uranium deposit depends on the relative distance between two resources. When the caved and fractured zone encroaches on the uranium deposit the coal seam should be abandoned. Conversely, when the uranium deposit lays in the constrained zone, the recovery of the coal seam would benefit recovery of the uranium deposit; (c) The feasibility of the co-recovery of the two resources can be optimized by the choice of mining approach. The top-caving mining approach and room-and-pillar mining approach can reduce the height of the caved and fractured zones and make the co-exploitation of the uranium and coal feasible. This work provides a new approach to investigate the feasibility of co-exploitation of uranium and coal.
The excavation of deep mining roadways with traditional mining methods leads to various issues, such as the occurrence of large deformations, the waste of coal resources, complex conditions and the ...high cost of advanced support measures. In this study, we examined the roadway damage mechanism of the traditional gob-side entry driving method with coal pillars using the Suncun Coal Mine, the deepest mine in China, as an engineering case study. A method for the automatic formation of roadways in deep mining areas by roof cutting with high-strength bolt-grouting was proposed, and several quantitative evaluation indicators, namely, the roadway deformation control rate, anchor cable strength utilization ratio, and hydraulic prop strength utilization ratio, were established. The impacts of controlling the deformation of the surrounding rock were comparatively analysed in consideration of numerous factors, such as the mechanical parameters of the surrounding rock, roof cutting height, roof cutting angle, grouting anchor cable length, and hydraulic prop spacing. On this basis, the proposed method was applied in the field. The results showed that the automatically formed roadway cross-section exhibited decreased convergence deformation; moreover, the roof deformation was effectively controlled, and the passive hydraulic prop supports could be effectively replaced with the active support of grouting anchor cables, verifying the effect of the proposed method.
Focusing on globalization in the late nineteenth and early twentieth centuries, Jessica Teisch examines the processes by which American water and mining engineers who rose to prominence during and ...after the California Gold Rush of 1849 exported the United States' growing technical and environmental knowledge and associated social and political institutions. In the frontiers of Australia, South Africa, Hawaii, and Palestine--semiarid regions that shared a need for water to support growing populations and economies--California water engineers applied their expertise in irrigation and mining projects on behalf of foreign governments and business interests.Engineering Natureexplores how controlling the vagaries of nature abroad required more than the export of blueprints for dams, canals, or mines; it also entailed the problematic transfer of the new technology's sociopolitical context. Water engineers confronted unforeseen variables in each region as they worked to implement their visions of agrarian settlement and industrial growth, including the role of the market, government institutions, property rights, indigenous peoples, labor, and, not last, the environment. Teisch argues that by examining the successes and failures of various projects as American influence spread, we can see the complex role of globalization at work, often with incredibly disproportionate results.
Gao et al discuss on top coal caving is one of the most effective methods for mining thick coal seams. The lop coal caving process leads to large-scale motion in the coal rock layer. Under the ...coupled influence of mining dynamics and gas pressure in the coal body, the mining-induced fracture field and primitive fracture field are superposed in the overlying rock layer, and the associated laws of temporal and spatial evolution are extremely complicated. Under the top coal caving conditions, the abutment pressure response lags behind the response of the characteristic values (fractal dimension and connectivity) as the mining-induced fractures evolve, and the average growth rate of the abutment pressure coefficient is higher than the fractal dimension and the one-dimensional connectivity of the fractures by a factor of 10-100.
•ASM is increasingly associated with heavy earth moving machines and hazardous chemicals use.•Governance challenges hindering formalization of the ASM subsector contributes to a burgeoning informal ...stream.•Process Net Map provides insights into governance challenges facing ASM and enables the identification of policy reform options to address them.
The artisanal small-scale mining (ASM) sector – commonly described as low-tech, labor-intensive mineral extraction and processing, in developing countries, is increasingly associated with the use of heavy earth moving machines and hazardous chemicals for ore extraction, which can have negative implications on agricultural land use and the environment. Moreover, land reclamation, or the lack thereof, associated with ASM is a rising concern. Despite the potentially far-reaching effects of informal ASM operations on the environment and human health, the legal framework for ASM, particularly in sub-Saharan African countries, is not well implemented. Focusing on Ghana as a study case, this paper explores the factors that hinder the implementation of its legal framework for mining. A combination of qualitative explorative methods was applied, including an innovative tool called “Process Net-Map”, a visual participatory mapping technique. The results help to explain the governance challenges of the ASM sector, enabling identification of policy reform options to address them. The findings exposed outdated legislature, which fails to capture the ever-growing complexities of the subsector’s operations, as a major bottleneck. Hurdles associated with formal licensing bureaucracies and fees, land tenure, compliance monitoring, and ineffective collaboration of relevant stakeholders with and at the local level were identified as hindering the implementation of the existing legal framework. These bottlenecks must be addressed. Moreover, we recommend the adoption of collaborative governance systems, like co-management, which has been successfully implemented in other disciplines, in the ASM sector to ensure sustainability.
Some villages and bridges are located on the ground surface of the working district no. 7 in the Wanglou Coal Mine. If longwall mining is adopted, the maximum deformation of the ground surface will ...exceed the safety value. Strip mining is employed for the working district no. 7 which is widely used to reduce surface subsidence and the consequent damage of buildings on the ground surface. To ensure the safety of coal pillars and improve the recovery coefficient, theoretical analysis and numerical simulation (FLAC 3D) were adopted to determine the coal pillar and mining widths and to discuss the coal pillar stress distribution and surface subsidence for different mining scenarios. The results revealed that the width of coal pillars should be larger than 162 m, and the optimized mining width varies from 150 to 260 m. As the coal seam is exploited, vertical stress is mainly applied on the coal pillar, inducing stress changes on its ribs. The coefficient of mining-induced stress varies from 2.02 to 2.62 for different mining scenarios. The maximum surface subsidence and horizontal movement increase as the mining width increases. However, when the mining width increases to a certain value, increasing the pillar width cannot significantly decrease the maximum subsidence. To ensure the surface subsidence less than 500 mm, the mining width should not be larger than 200 m. Considering the recovery coefficient and safety of the coal pillar, a pillar width of 165 m is suggested.
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