Assessing Impacts of Mining Activities on Land Use/Land Cover Change Using Remote Sensing and GIS Techniques: A Case Study in Campha City, Vietnam

Coal is one of the most mining commodities to date, especially to supply both national andinternational energy needs. Coal mining activities that are not well managed will have an impact on theoccurrence of environmental damage. The present study was undertaken to analyze the process of humaninducedlandscape transformation in the coal mines affected areas of Cam Pha, northeast Vietnam byinterpreting temporal remote sensing data and using Geographic Information System. This experimentrevealed that most of the study area was dominated by forest in all the time sequence period. The forestcover has decreased about 21.3%, meanwhile having nine fold increase in mining area from 1990 to 2020.The forest area lost during the study period was 7983.45 ha due to land cover conversion into mining area.The mining activities were also detrimental to the bare land and water body cover. The results of this studyare expected to be used to support government efforts and mining managers in post-mining coal activities.

Applying Artificial Pillar to Replace the Coal Pillar Protecting Roadway to Increase Production Efficiency and Sustainable Development in the Vietnamese Coal Industry

Vietnam's domestic coal production is growing fast and is expected to reach 68.9 million tonsin 2030, nearly 1.5 times higher than today. Open-pit mines will gradually reduce production and close,and underground mining coal output will increase progressively year by year and take a leading role.Besides the investment in new mines to achieve these goals, it is necessary to maximize the coal reserveexploited annually of existing underground mine projects, which its coal reserve in pillars protectingroadways currently accounts for 12−15%. The further exploitation of this coal reserve will decrease thecosts of preparation of underground mines and granting mining rights and depreciation of infrastructureassets. Moreover, it will help reduce the loss of non-renewable resources and contributing to thesustainable development of Vietnam’s coal industry.

Characteristics of Overburden Failure and Fracture Evolution in Shallow Buried Working Face with Large Mining Height

In order to solve the issues of uncertain overburden failure height and water loss at the Daliuta coal mine, the collapse characteristics of overburden and the development height of water-conducting fractured zone were studied by using physical modeling, FLAC 3D numerical simulation, and field observation, which were used to verify each other. In order to quantitatively analyze the distribution characteristics of fracture rate of overlying rock mass in goaf, the overburden collapse image was binarized. The results showed that: (1) the failure characteristics of overburden in goaf obtained by the three research methods were roughly consistent, and the reliability of the results was high. The overburden failure height of No. 5−2 coal with large mining height was 137.32–153 m, which was 20.8–23.2 times the mining height. (2) The repeated mining of No. 5−2 coal intensified the further failure of the disturbed rock mass in the No. 2−2 coal goaf. (3) In the horizontal direction of the goaf, the fracture rate of rock mass was distributed in the shape of “saddle”. In the longitudinal direction of the goaf, the rock mass fracture rate decreased in a logarithmic function with the increase of the height from the mining coal seam. Overall, the conclusions are of engineering significance for accurately adopting water resources protection mining technology and reducing mine water inrush disasters.

Health Impacts of Air Pollution in Chinese Coal-Based Clean Energy Industry: LCA-Based and WTP-Oriented Modeling

The evolution of energy system occupies an important position in economic development and quality of life. Influenced by the energy endowment in China, developing the coal-based clean energy industry has been regarded as a guaranteed path to realizing the clean and efficient use of coal resources. However, an evaluation paradigm could systematically assess the health impacts of airborne pollution in this industry is still lack, which is our concern. Combining with life cycle analysis, probabilistic risk models, and health impacts models, this study proposes a series of models which are consistent enough to unite pollutant concentration, health risk, and health impact, and equip assessment results with more intuitive significance using life and economic loss. Further, case studies for three typical coal-based clean energy processing, namely, coal mining, coal-fired power generation, and coal liquefaction are presented to verify the reliability of these models. It is proved that this evaluation paradigm can help to find out the worksite, substage, and airborne pollutant with the most severe impact, and more importantly, the application of evaluation indicators with life and economic meaning is more profitable to provide references for minimizing or eliminating the health impacts, moreover, explicit the developing directions of the national energy industry.

VCAM-1 Is Upregulated in Uranium Miners Compared to Other Miners

The United States has a rich history of mining including uranium (U)-mining, coal mining, and other metal mining. Cardiovascular diseases (CVD) are largely understudied in miners and recent literature suggests that when compared to non-U miners, U-miners are more likely to report CVD. However, the molecular basis for this phenomenon is currently unknown. In this pilot study, a New Mexico (NM)-based occupational cohort of current and former miners (n = 44) were recruited via a mobile screening clinic for miners. Serum- and endothelial-based endpoints were used to assess circulating inflammatory potential relevant to CVD. Non-U miners reported significantly fewer pack years of smoking than U-miners. Circulating biomarkers of interest revealed that U-miners had significantly greater serum amyloid A (SAA), soluble intercellular adhesion molecule 1 (ICAM-1, ng/mL), soluble vascular cell adhesion molecule 1 (VCAM-1, ng/mL), and VCAM-1 mRNA expression, as determined by the serum cumulative inflammatory potential (SCIP) assay, an endothelial-based assay. Even after adjusting for various covariates, including age, multivariable analysis determined that U-miners had significantly upregulated VCAM-1 mRNA. In conclusion, VCAM-1 may be an important biomarker and possible contributor of CVD in U-miners. Further research to explore this mechanism may be warranted.

Study on Reasonable Stopping and Time-Sharing Partition Support of Fully Mechanized Top Coal Caving Face Under the Interference of Stopping Line in Close-Up Coal Seam

Close-distance coal seams are widely distributed in China, and there is a problem of stopping mining in a large number of working faces. Taking Yanzishan mine as the engineering background, the mined-out area and the remaining end-mining coal pillar of No.4 coal seam (upper coal seam) mined in advance caused strong interference to the stopping mining of N316 working face of No.3 coal seam under it. Through field observation, laboratory experiment, and support data collection, the mechanical parameters of coal and rock mass and periodic weighting condition of the working face were mastered, and numerical simulation and similar model experiments were carried out. Three positional relationships between the stopping position of the underlying N316 working face and the upper stopping line were obtained: “externally staggered with the upper stopping line” (ESUL), “overlapped with upper stopping line” (OUL), and “internally staggered with the upper stop line” (ISUL, ISUL-SD for shorter internal staggered distances, ISUL-LD for longer ones). The formation and evolution of the stress arch structure of ESUL → OUL → ISUL-SD → ISUL-LD are obtained from the analysis: ① ESUL: there is a double stress arch structure of goaf side and end-mining coal pillar side in the overburden and stress superposition appears in the middle arch foot (stopping mining place). ② OUL: it evolved into a single arch structure of goaf-solid coal, and the stress at the stop of mining was relatively minimum. ③ ISUL-SD: it is still a single arch structure, and the stress at the stop of mining is still small. ④ ISUL-LD: the double stress arch is regenerated and stress superposition occurs at the front arch foot (stopping mining place). At the same time, the morphological evolution process of stress arch is as follows: “front and back stress arches, superimposed with middle arch foot” → “front arch gradually decreases” → “front arch dies, and two arches merge into single arch” → “single arch gradually increases” → “two arches are regenerated, superimposed with front arch foot”. On-the-spot analysis from the combination of stress and overburden structure: ① ESUL: the stress concentration degree is the highest above the stopping space, and the overburden block in the large-scale caving zone directly acts on the support, which makes the stopping operation difficult. ② OUL: although the stress environment is the best, the overlying key blocks will have hidden dangers of overall rotation or sliding instability. ③ ISUL-SD: the stress environment is good, and the overlying rock can realize the stable structure of the cantilever plate (the internal staggered distance is less than the periodic weighting step), and the mining is stopped at this position to realize the safe and smooth withdrawal of the support. ④ ISUL-LD: it is basically consistent with stopping mining when single-layer coal is used but is limited by the limited length of the end-mining coal pillar. In addition, the self-digging retracement channel is designed to serve the whole retracement process, and the idea of time-sharing partition support for a large cross-section of mining stoppage and its corresponding scheme is put forward according to the retracement process. Through the simulation of prestressed field and field practice, the roof overlying rock structure is stable during the whole retracement period, thus realizing the safe and smooth mining stoppage and retracement of the working face.

Research on Special Support Technology of Gob-side Entry Retaining with Filling the Non-roadway Side in the Thin Coal Seam

By taking a certain mining area of No.2 coal seam in a coal mine as the research object, special support technology of gob-side entry retaining with filling the non-roadway side was researched. Based on the geologic features of this mining area, support method of gob-side entry retaining was proposed. The method replaced the dense wood prop with single prop, and cooperated intersection hinge roof. The support parameters were calculated, and time-space coordination between each support process was researched. The field measured data showed that this support method had a remarkable effect and strictly controlled the deformation of gob-side entry. This research formed a support system and mining system based on this condition. It has important reference meaning to safe and efficient mining coal resource with similar geologic condition.

Numerical simulation study of mining process of upper and lower walls of normal and reverse faults

Mining coal seams near faults are prone to various mine disasters, and different mining sequences have different effects on coal seam disasters. Under this background, the numerical models of normal fault hanging wall, normal faultfoot wall, reverse fault hanging wall and reverse fault footwall under the same geological conditions are established. It is found that the stress concentration of coal pillar is the largest in the mining process of hanging wall of normal fault and footwall of reverse fault, and the possibility of inducing coal pillar rockburst is the largest. Affected by the fault, the coal pillar abutment stress between the working face and the fault shows an upward trend. When mining the coal seam near the fault, various methods such as hydraulic fracturing should be adopted to reduce the coal pillar abutment stress and reduce the risk of mine disasters.

The Role of the Reverse Fault on the Permeability Evolution in Mining Coal

To prevent and control the coal seam gas disaster affected by the reverse fault, we performed gas seepage tests, which consider stress-loading and unloading schemes, to investigate the stress change and coal permeability of the mining coal with reverse fault. The experimental results show that the mechanical behavior and permeability change of the mining coal are related to the distance between the coal and the reverse fault. The stress concentration coefficient of the coal body gradually increases. The closer is the distance between the coal and the reverse fault, the larger are the deviatoric stress peak and strain. In comparison with the coal sample M1 that is 5 m away from the reverse fault, the deviatoric stress peak and axial strain of the coal sample M3, 35 m away from the reverse fault, increase by 40.74% and 26.73%, respectively. In this stage, the permeability of M1, M2, and M3 coal samples increases by 22.1%, 28.0%, and 36.7%, respectively. In another stage, the stress concentration coefficient of coal increases to the peak and then decreases, causing the deviatoric stress peak and strain of coal to rise first and then fall. In comparison with the coal sample M4 that is 65 m away from the reverse fault, the deviatoric stress peak and axial strain of coal sample M6, 5 m away from the reverse fault, decrease by 29.48% and 5.55%, respectively. The permeability of coal samples M4, M5, and M6 increases by 23.6%, 37.2%, and 20.8%, respectively. Based on the gas seepage test results, we established the permeability model of mining-induced coal under the influence of a reverse fault, with consideration of the volume changes of coal fractures induced by adsorption and desorption. In the model, the variations of permeability in both stages of the prepeak and postpeak were deduced, which was verified with the experimental data. The verification results demonstrate that the proposed model has the capacity to predict the permeability evolution of mining coal under the influence of a reverse fault.

Application of Transient Electromagnetic in Detection of Water Accumulation in Broad Coal Mine

In view of the problem of serious water accumulation and frequent accidents in the coal mine mining area, the distribution range of Yuzhou Shenhuo Kuanfa Mining Coal (hereinafter referred to as Kuanfa Coal Mine) is detected by transient electromagnetic method. The transient electromagnetic emission wire frame is 480m × 480m, frequency is 8Hz, power supply current is 16A. The research conclusion preliminarily determines that the transient electromagnetic and controllable source audio earth electromagnetic method is applicable for the exploration of the mined space area in Yuzhou mining area, and the construction parameters provide a reliable reference for the accurate exploration of the mined space area in Kuanmining area.