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Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Huayingshan coalfield is one of the most important coal districts in Southwest China. Coal mining may have an impact on the hydrochemical characteristics and regional evolution of karst groundwater. This study aims to analyze the hydrogeochemical characteristics, identify the evolution processes, and influencing factors that govern the hydrochemistry in multilayer karst aquifers in the coalfield. Statistical methods and conventional techniques were utilized to gain a thorough understanding of the origin and hydrogeochemical evolution of karst groundwater. The results revealed that the groundwater was fresh water and natural to mildly alkaline. It suggested that the relative abundance of main ions was proposed to be Ca2+ Mg2+ > K+ + Na+ for cations and > Cl– > for anions. A Piper diagram of the investigated water samples demonstrated that most groundwater was of the HCO3-Ca type. The results showed that dissolution of carbonate, gypsum, halite, and silicate minerals highly influenced the formation of , , Ca2+, Mg2+, and Na+. Cation exchange and/or absorption was another important regulatory process. concentrations were excessively high, proving that karst water was affected by agricultural activities in certain aquifers. Moreover, S2– concentrations were high in the borehole and mine tunnel samples, suggesting great acidification potential. Coal mining carries a risk of deteriorating the local water environment. This exposes sulfide minerals to oxygen and water, increases concentration, and reduces groundwater pH. Scientific research must focus on specific recharge area locations, runoff and drainage pathways, and hydrochemical evolution processes of karst water, and the contact of sulfide with water and oxygen must be controlled to protect groundwater quality and reduce pollution. The results suggest it may be helpful for investigation and treatment of water environment pollution, aid the protection of karst groundwater in the Huayingshan coalfield, and serve as a model for other comparable studies. [ABSTRACT FROM AUTHOR]

To comprehensively understand the influence of mining speed on gas emissions in goaf during coal seam extraction, enhance gas extraction efficiency in goaf, manage gas emissions at the working face, and ensure safety in the mining production process. This study focuses on the No. 3 mining area of Wangjialing Mine, employing numerical simulations to analyze the evolution of mining-induced fractures and the characteristics of gas distribution in the overburden at varying mining speeds. Furthermore, by integrating actual gas emission and extraction data at the production face, this study examines the quantitative relationship between mining speed and gas emissions in the goaf, identifying optimal regions for high-position borehole layouts and conducting borehole optimization design and investigation. The results of this study indicate that the initial caving step distance of the goaf roof increases with the advancement speed of the working face. Conversely, the maximum height of through fractures in the overburden decreases as the mining speed increases, while delamination fractures are minimally affected by the advancement speed. By categorizing and averaging data on goaf mining speed, the impact of initial and periodic pressure on gas emissions can be effectively mitigated, revealing a linear correlation coefficient of 0.94 between goaf gas emissions and mining speed. At varying mining speeds of the working face, the efficient extraction layer and horizontal distance parameters of gas extraction boreholes in the goaf conform to the linear equation y = ax ± b. Based on the research findings, an optimization design for mining face speed and high-level borehole parameters in the goaf was implemented. The average gas extraction rate of high-level directional boreholes reached 68% throughout the extraction period. Gas emissions at the working face were effectively controlled below 10 m3/min, with the maximum gas concentration at the upper corners and return airflow kept below 0.8%. This effectively managed gas emissions at the working face, ensuring safe production in the mine, providing a theoretical basis for identifying gas-rich areas in the mining-induced overburden, and enhancing gas extraction efficiency at the working face. [ABSTRACT FROM AUTHOR]

Purpose. This study aims to investigate fluid flow and heat transfer within rocks containing boreholes, focusing on the complex mechanisms within hot reservoirs. Non-commercial finite element (FE) software is used to visualize and present the results. Methods. The study involved the use of FE method with Visual Finite Element Analysis (VisualFEA) software to analyze the coupled phenomena of fluid flow and heat transfer in a rock sample. Special attention was given to incorporating material structure and geotechnical analysis in the software, as well as the treatment of cracked elements. In addition, the validation was done by comparing the current numerical solution using VisualFEA with the numerical solution using ANSYS Software. Findings. The study findings highlight the capabilities of VisualFEA software to accurately represent fluid flow, stress, and heat transfer in borehole-containing rocks. The results include insights into flow direction within the borehole, temperature distribution, and the validation of the software performance against expected system behavior. The study demonstrates the effectiveness of VisualFEA in handling complex loading and its ability to visualize multiple flow directions within a 2D model. The results are presented in the form of contours and curves. Originality. This study contributes to the field demonstrating the application of VisualFEA software in analyzing fluid flow and heat transfer in rocks with boreholes. The focus on incorporating material structure, geotechnical analysis, and treatment of cracked elements adds originality to the study, providing a comprehensive understanding of the coupled phenomena in hot reservoirs. Practical implications. The practical significance of this study is in the validation and benchmarking of VisualFEA software for studying fluid flow and heat transfer in geotechnical application. The findings can be utilized by geotechnical engineers and researchers to better understand the behavior of borehole-containing rocks under specific pressure and thermal loading conditions. The insights gained from this study can be used in decision-making processes related to resource mining, reservoir engineering, and geothermal energy use. [ABSTRACT FROM AUTHOR]

Borehole engineering encompasses the part of mining that involves the process of drilling boreholes and their utilization (e.g., for research, exploration, exploitation, and injection purposes). According to legal regulations, mining pits must be closed after their use, and this applies to pits in the form of boreholes as well. The Laboratory of Geoenergetics at AGH University of Krakow is involved in adapting old, exploited and already closed boreholes for energetic purposes. This includes geothermal applications, as well as energy storage in rock formations and boreholes. Geoenergetics is a relatively new concept that combines geothermal energy with energy storage in rock formations (including boreholes). One type of analysed borehole is a freezing borehole. They are used, for example, in drilling mining shafts that are in the vicinity of aquifers and are drilled using the rotary drilling method with a reverse circulation of drilling mud, or in peat bogs. For borehole heat exchangers based on freezing boreholes for long-term mathematical modelling, several heating scenarios were considered with several thermal loads. The maximum average power obtained after one year of usage of four boreholes with variable temperatures was 11 kW. With the usage of 10 boreholes the power reached over 27 kW. The heat-carrying temperature was assumed to be 22 °C during early summer (June and July) and 2 °C during the rest of the year. When considering stable exploitation during a 10-year period with four boreholes with the same temperatures, a heating power of over 12 kW was obtained, as well as a power of over 28 kW when considering using 10 boreholes. The maximum amount of heat obtained during the 10-year period using 10 boreholes was over 8.8 thousand GJ. Once they have fulfilled their function, these boreholes lose their technological significance. In the paper, the concept is outlined, and the results of the analysis are described using the numerical program BoHEx. [ABSTRACT FROM AUTHOR]

This study aimed to examine gas extraction technology in the goaf of an L-shaped borehole in the mining fissure zone of a short-distance coal seam group. The numerical simulation method was used to analyze the failure law of overlying rock during mining, and a mathematical model was established for gas migration in the mining overburden. Finally, gas extraction tests were performed for the L-shaped borehole in the mining fissure zone. The results showed that as the coal mining project progressed, the damage area of the overlying strata in the goaf became larger, and the plastic damage area of the overlying rock along the strike had a saddle shape, being concave in the middle and convex at both ends. The closer the L-shaped borehole in the mining fissure zone was to the coal seam roof, the greater the amount of air leaking from the working face into the goaf, and the lower the overall gas concentration in the goaf. When the vertical distance of the L-shaped borehole was too high, the ability of the L-shaped borehole to control the gas concentration in the lower goaf was weakened. Moreover, the mining fracture zone was a good space for gas migration and storage. Thus, arranging the L-shaped borehole in this zone can greatly improve the efficiency of borehole gas extraction. According to the overlying rock conditions and mining conditions of Tunlan Mine, the L-shaped borehole was positioned 43 m away from the roof of the coal seam. The extraction rate of the L-shaped borehole reached 9.30 m3∙min−1, and the gas concentration in the corners of the working face was kept below 0.4%, yielding an excellent extraction effect. [ABSTRACT FROM AUTHOR]

Drill core samples from a lignite-mudstone succession with variations in organic matter maturity from Troyanovo-3 Mine (Mini Maritsa Iztok EAD) were analyzed for trace element contents. All elements except Hg and Th show one positive spike in their distribution, located at different depths. Molybdenum and Ni peak at the deep level (52.6-3 m); Fe, V, As, Hg, Zn, U, and Th peak at 29.3-29.5 m; Pb and Cu peak at shallow depth - 19.2-20.1 m. All measured concentrations are much higher than the Clarke for low rank coal and sedimentary rocks and comparable with published data for black clays from Troyanovo-3 Mine. The lack of significant correlation between total organic carbon and all analyzed trace elements points to other hosts for the trace elements. The strong positive correlations found for Fe and V, Ni, Cr, As, and Mo suggest incorporation of these elements into Fe sulfide phase(s). The strong positive correlations for Al and Ni, Co, Mo and U, and a weak correlation between Al and V suggest a terrigenous and/or sorbed form of presence. The lack of a strong correlation between mercury and total organic carbon, ash, sulfur and uranium confirms the well-known complex Hg affinity. Our previously outlined hypothesis for OM enhanced maturity as a result of ascended hydrosulfide injection is here further supported by the trace element differentiation at different depths. [ABSTRACT FROM AUTHOR]

Previously conducted studies have established that the early warning of water inrush is crucial for the prevention and control of mining water catastrophes in the panel. In order to ensure the safety of coal mining, in this paper, monitoring indicators were determined using the sensitivity analysis method, and then a multi-indicator early-warning model for water inrush was established mainly based on the geological data of the Yanghuopan coal mine. The monitoring stage of the early-warning model should be determined according to the distance between the monitoring borehole and the mining position. Then, the development of a water-conducting fracture zone and the fluctuation and stochastic oscillator of monitoring indicators are comprehensively analyzed to determine the early-warning level. A multi-indicator early-warning model was applied to panel 30302 of the Yanghuopan coal mine and panel 1304 of the Zhaoxian coal mine in the Yushen mining areas. The abnormal warning of the water disaster in panel 1304 was sent 3 days before the disaster, which shows the effectiveness of the model. It can provide a reference for the development of an early-warning model for mine water inrush in Yushen mining areas. [ABSTRACT FROM AUTHOR]

Daddy long-legs spiders are common inhabitants of tropical and subtropical caves around the globe. Numerous species have evolved troglomorphisms, including the loss of body pigments and eyes. Here we describe the first troglomorphic pholcids from Australia and Réunion. Belisana coblynau Huber & Clark, sp. nov. was extracted from mining boreholes in the arid West Australian Pilbara region. It represents a genus that is widespread in tropical forests of South and Southeast Asia, reaching the tropical north and east of Australia. Belisana coblynau is thus presumably a relict whose epigean ancestor lived in the area before the aridification of Australia starting in the early Cenozoic. Buitinga ifrit Huber & Cazanove, sp. nov. was collected in Grotte de La Tortue on Réunion, one of the oldest lava tubes on the island (~300,000 years). Congeneric species are known from East Africa, and the genus does not seem to have reached Madagascar. Since Pholcidae do not balloon, the now extinct epigean ancestor of Buitinga ifrit probably reached the island by highly accidental means (such as rafts or storms). [ABSTRACT FROM AUTHOR]

Fractures are ubiquitous in Earth's upper crust and strongly affect its physical properties. Their visibility for elastic waves hinges on their stiffness, a measure of the relation between changes in fracture aperture and applied stress, which itself significantly increases with increasing stress according to laboratory data. We constrained normal stiffness (and its stress dependence) of two fractures intersecting a borehole in the research mine 'Reiche Zeche' in Freiberg, Saxony, Germany, from pressure-recovery behaviour observed when the pressure in a double-packer interval enclosing them was briefly released during shut-in sequences. For the evaluation of the pressure recovery, we developed a generic model that accounts for the inherent convolution of mechanical closing of the fracture, fluid flow in the fracture, fluid exchange between fracture and the surrounding rock, here addressed as fracture leakage, and effects associated with finite borehole storage. We address the hydraulic system by considering three different 'storage containers', described by non-dimensionless storage parameters: the wellbore with a fixed storage capacity, the fracture with storage capacities related to fluid compressibility and fracture stiffness, and the surrounding rock constituting a container with unlimited storage capacity. To examine the model's characteristics, we investigated pressure transients predicted for specific cases, such as negligible fracture leakage, and subsequently numerically determined the sensitivity of the model predictions to the involved model parameters. The model's application to the field data yield estimates of properties of the fractures (length, aperture and stiffness) and of the surrounding rock mass (product of permeability and specific storage capacity). The parameters derived from the modelling compare well with independent constraints. An analysis of currently available fracture-stiffness data shows that the lack of knowledge of the stress dependence of stiffness severely hampers firm conclusions on scale dependence and the bias between methods. [ABSTRACT FROM AUTHOR]

Dust pollution has long been a challenge in the blasting excavation of underground metal mines, and uncontrolled diffusion of dust particles seriously endangers the health and safety of workers as well as the environment in underground space. Most existing research on dust diffusion focuses on fully mechanized coal mining face or borehole drilling, where the dust source emission characteristics differ significantly from metal mine blasting excavation. Furthermore, it is still unclear how the ventilation modes of Far-Pressing-Far-Absorption (FPFA), Near-Pressing-Far-Absorption (NPFA), and Far-Pressing-Near-Absorption (FPNA) affect the mechanism of dust diffusion in the breathing zone. In this work, gas-solid flow characteristics in a typical metal mine blasting tunnel are numerically studied based on Euler-Lagrange method. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by the discrete random walk model. Five typical regions for airflow disorder phenomena in the working tunnel are predicted, including the jet development region, the return airflow core region, the airflow reversal region, the airflow recirculation region, and the secondary flow region. The spatial distribution of dust exhibits nonuniform characteristics under turbulent airflow transport. The time results of the monitored dust concentration reveal that the junction of the working tunnel and the return airway is a key area of focus for the prevention and control of dust pollution. Among the three ventilation modes, the Far-Pressing-Near-Absorption (FPNA) ventilation mode has the best dust removal efficiency. The supply vent further from the blasting face allows the jet to fully develop, while the exhaust vent closer to the blasting face allows dust particles to be drawn in and discharged earlier. Under the condition of fixed total power consumption for the supply and exhaust fans, a larger exhaust airflow velocity helps remove dust from the breathing zone. [Display omitted] • Two phase flow of air and dusts in underground metal mine tunnels are simulated. • Effects of three hybrid ventilation modes, FPFA, NPFA, and FPNA, have been revealed. • Far-Pressing-Near-Absorption ventilation mode has the best dust removal efficiency. • Effects of supply and exhaust air flow rates on dust diffusion are revealed. • Five typical regions for airflow disorder in the working tunnel are predicted. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The features occurring during borehole uranium mining in deposits with low filtration characteristics, as well as the conditions and reasons for the reduction of geotechnological parameters of uranium mining by the well are considered in this study. Core material samples were taken from the productive horizon of the Chu-Sarysui province deposit and granulometric compositions were established. The contents of uranium, aluminum, calcium, magnesium, iron and carbonate minerals in the samples were determined by atomic emission spectroscopy. The X-ray phase analysis method established the features and quantitative and qualitative characteristics of ore-containing minerals. A special technique has been developed for conducting experiments in laboratory conditions using core samples, where the intensity of uranium leaching in tubes is determined. The results of laboratory studies are analyzed and discussed and graphs are constructed, to show the dependencies of change in: the filtration coefficients of Kf; the uranium content in solution; the extraction coefficient; and the specific consumption of sulfuric acid on the values of L:S (the ratio of liquid to solid) in the experiments. The effectiveness of using a mild acidity regime, with the addition of oxygen as an oxidizer, is determined and shown. The values of the uranium content in the productive solution, with the addition of oxygen as an oxidizer, reached 220 mg/L, which exceeds the design parameters. The results of uranium extraction from ore show a positive trend, reaching 68%, with L:S from 1.7 to 3.0, low acidity values and the addition of oxygen as an oxidizer. The specific consumption of sulfuric acid reaches the minimum values when using leaching solutions with reduced acidity of 26 kg/kg. The obtained results, on the flow rate of the solution in the tube, the extraction of uranium from ore and the specific consumption of sulfuric acid, indicate a decrease in sedimentation in a porous medium and increased filtration characteristics, with reduced acidity values in the leaching solution. [ABSTRACT FROM AUTHOR]

The article presents the impact of lignite mining on the environment associated with the introduction of hydro borehole mining (HBM) technology. The results are partially based on the HydroCoal Plus project results, where an environmental assessment of lignite HBM technology was performed. In order to reach the goals of the task, a life cycle assessment (LCA) study was used to assess selected environmental aspects of the HBM single-borehole lignite production process covering selected environmental impact categories such as energy consumption, fuel consumption, water consumption and carbon footprint. The LCA procedure was adapted in an innovative way, constituting another added value to the shown research. The second part of this paper describes opportunities identified by the authors to minimize the environmental impact of lignite production by implementing the HBM method compared to the conventional opencast method. [ABSTRACT FROM AUTHOR]

The whole borehole is divided into severat wett secions wtth different fricion factors by uiing system duster anatysis. Combined wtth the dritt string friction torque modet, the simulated anneating algorithm is used to inverse and caiculate the opiimat vatue of friction factor of each wett secion. Based on the sectionat friction factor, considering the bearing capadty of the dritting rig, rock crushing condl-ions, friction condtiions, diitt stiing strength condtions and diitt stiing siffness condtiions, the judgment criterion and predicion modet of horizontat wett extenrion iimtt are estabiished. The field appiicaiion resutts show that the predicted vatues of hook toad and wetthead torque obtained by the segmented fricion factor inversion method have a good correlation with the measured data. The average absolute error vatues are 3. 72% and 3. 45% respertivety, which are 54. 8% and 51. 8% higher than the predicion accuracy of the tradtionat inverrion method. Wtth the increase of friction factor, the extenrion limtt of horizontat well decreases obviousty. The resutts can provide a reference for the predicion of extenrion iimtt of horizontat well. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The determination of propulsive abutment pressure and deformation characteristics of roadway surrounding rock mass in top-coal caving mining is of great significance for further research on mining stress, roadway support and equipment selection. This paper adopts the method of combining theoretical analysis and field test, taking Helin coal mine j7401 working face as the research object. The relationship between abutment support pressure and roadway surrounding rock mass deformation is revealed by monitoring the stress of transportation and ventilation roadway and observing the deformation of mining roadway. The main conclusions are as follows: when the distance between top-coal caving mining and borehole is about 65 m, the borehole stress begins to exceed the original rock stress, and the peak of the abutment pressure is 15–22 m in front of the working face, ranging from 33 to 39 MPa, which is 3.2–3.8 times the original rock stress. The intersection of propulsive abutment pressure curve and original rock stress curve is located at 8.1 m in front of the working face, the boundary of roadway rapid deformation stage and deceleration deformation stage is 8.9 m ahead of the working face, the distance between the two stages is 0.8 m, and the peak position of propulsive abutment pressure is 19.8 m. The boundary of roadway decelerative deformation stage and stationary small deformation stage is 20.1 m, and the distance between the two stages is 0.3 m. The boundary between the fracture zone and the limit equilibrium zone is the intersection of the propulsive abutment pressure curve and the original rock stress curve. The plastic zone is constituted by the damage zone and the limit equilibrium zone, and the boundary between the plastic zone and the elastic zone is located at the peak of the propulsive abutment pressure. The above study results provide a basis for roadway support and efficient coal mining. [ABSTRACT FROM AUTHOR]

Native sulphur deposits mined using the underground melting method are characterized by a complex structure, which is the result of the many geologic processes which led to their formation. The resource utilization rate and the consumption of hot water per ton of sulphur are the main criteria of mining effectiveness. They depend on the porosity and permeability of the rocks forming the deposit, the content and mode of occurrence of sulphur (ore texture), and the distribution of rocks with these varying features. Good recognition of geological and hydrogeological deposit features, exploitation results, is important for formulating the rules of controlling the course of exploitation in order to achieve the best recovery of sulphur with the lowest possible water consumption and to reduce operating costs. Sulphur deposits are characterized by great local and directional variations in their structure and hydrogeological parameters. This makes the melting process irregular. The flow of hot water and melted sulphur is facilitated in certain directions. As a result, the shape, and distribution and form of exploited parts of the deposit are highly variable. Full information about the deposit is necessary for the proper understanding and prediction of processes that occur in the deposit during sulphur melting, for forecasting its effects, and for controlling the exploitation process. This information is obtained through the lithological description of core samples from exploratory and exploitation boreholes, geophysical borehole logging, and surface seismic surveys. [ABSTRACT FROM AUTHOR]

Copyright of Mining of Mineral Deposits is the property of Dnipro University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mining of Mineral Deposits is the property of Dnipro University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To figure out the distribution law of three spontaneous combustion zones in the goaf area of fully mechanized working face under high ground temperature, this study took the 11501# fully mechanized mining face of Zhujixi Coal Mine as the research object, and employed software Fluent to perform numerical simulations on the O2 concentration distribution in the goaf; then, combining with the actual situations on the site, the highlocation boreholes and grout holes of the roof gas drainage roadway of the 11501# working face were selected as measuring points to measure the O2 concentration changes in a few positions such as in middle part of the goaf, on the air intake side, and on the air return side. The results show that, the numerical simulation results were basically consistent with the field measurement results, in the middle part of the goaf, the scope of the oxidation zone was 26.4m-62m; on the air intake side, the scope of the oxidation zone was 32m-96m; on the air return side, the scope of the oxidation zone was 28.4m-91m. The research findings of this paper provided a scientific reference for formulating fireprevention and fire-extinguishing technical plans for mines. [ABSTRACT FROM AUTHOR]

Mining contributes to the creation of degraded areas that are difficult to rehabilitate because they are subject to various transformations. Specifically, sulphur mining using the Frasch borehole method causes multidirectional changes of soil properties and thus presents challenges for post-mining rehabilitation. The aim of the current study was to evaluate the effectiveness of agricultural (meadow-type) reclamation and to understand how the soil recovers over time by assessing the spatio-temporal variability of the reclaimed soil after borehole sulphur mining. Selected soil properties and spectral indices based on satellite data were analysed: before reclamation, 3 years after reclamation and 15 years after reclamation. Texture, bulk density, porosity, water capacity, total organic carbon (TOC) and pH were measured and distribution maps of these parameters were generated using kriging. Additionally, maps of spectral indices (Green Normalized Difference Vegetation Index, Normalized Difference Soil Moisture Index, Soil Adjusted Vegetation Index, Enhanced Vegetation Index and Red–Green Index) based on Landsat imagery were created to support the field survey data. The soil revealed high temporal and spatial variability, as evidenced by the distributions of measured parameters and their coefficients of variation at different reclamation stages. Multidirectional remodelling of the soil structure occurred, resulting in changes in the differential porosity, field water capacity, texture, reaction and TOC. Statistically confirmed differences in soil parameters between sampling points were observed. The variability of the physical and chemical parameters at the individual sampling point also differed between the reclamation stages. We observed a general trend towards homogenisation of the spatial distributions of the soil parameters. This was also confirmed by the maps of spectral indices, which showed establishment and development of a continuous vegetation cover and the subsequent improvement of its condition. [Display omitted] • Effect of agricultural rehabilitation on degraded post-mine soil was evaluated. • Spatio-temporal variability of soil properties after borehole mining was analyzed. • We used field survey data, geostatistics and satellite vegetation indices. • Spatial variability of physico-chemical soil parameters decreased over time. • Reduced soil variability enabled positive effects of reclamation. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

During the full-mechanized caving mining, the overburden strata in the double system and extrathick coal seam of the Datong mining area are largely damaged. Water and harmful gas in the old goaf may be discharged when overburden fractures evolve to the upper goaf, which poses a major threat to the normal production of the panel. To study the movement of overburden strata and the evolution of fracture field under the full-mechanized caving mining of the double system and extrathick coal seam, panel 8309 of Tongxin mine was taken as the research object; the evolution rule of fracture field in the full-mechanized caving mining of the double system and extrathick coal seam was obtained through field measurement and physical similar simulation. The results show the following: (1) the far-field and near-field key strata play a decisive role in controlling the fracture evolution of overburden strata. When the far-field key strata break and the development height of fractures reaches 220.9 m, panel 8309 is connected with the overburden goaf. (2) Based on the "O-shape circle" theory of mining fracture, with the continuous advance of the panel, the overburden breaks periodically, and a "fracture surface" with a certain angle of 61°–67° can be formed along with the advancing direction of the panel. (3) When the key strata are broken and the development height of fractures reaches the maximum, the fracture surface is formed as the "main fracture surface," which is the only downward discharge pathway for goaf water and harmful gas. The overall shape fracture surface is "inverted trapezoid" in the upper part and "positive trapezoid" in the lower part. (4) Based on the field measurement of the water level of borehole and the observation of mine pressure, the correctness of the evolution law of the similar simulated fracture field is verified. [ABSTRACT FROM AUTHOR]

To determine the failure characteristics and evolution regularity of the floor strata during fully mechanised top-coal cave mining in typical deep and extra-thick seams in western China, the 61303 working face of an Ordos mine was selected as the engineering research object. A comprehensive monitoring method combining a BOTDR (Brillouin Optical Time-Domain Reflection) distributed fiber strain test and a borehole resistivity CT (Computerised Tomography) test was adopted. The results show that floor stress distribution of the deep-buried and extra-thick coal seam is significantly affected by the different depths of rock lithology. At the interface of the rock strata with a large difference in the elastic modulus, phenomena such as the asynchronism of strata movement and obvious differences in failure easily occur. The failure depth of the floor strata in the 61303 working face is approximately 15.90 m, and the influence depth of the floor disturbance is approximately 32.70 m. Under the influence of the mining pressure, floor stress distribution and crack evolution have obvious spatial and temporal effects. In different inclined boreholes, the data captured by the cable have different values and the fracture locations of the cable also differ. Compared with a single borehole, multiple boreholes with different inclinations, directions and locations can provide more comprehensive and reliable data trends. The knowledge obtained by this monitoring can provide reference information for the study of floor damage under similar conditions and the formulation of technical measures such as those that prevent mine water disasters. [ABSTRACT FROM AUTHOR]

In 2010, South Korea’s nuclear power reactors generated 31.4 percent of the country’s total electricity—by 2030 the government plans to have 19 more reactors online, increasing even more the country’s total nuclear generating capacity. But with this increased capacity comes increased spent nuclear fuel. The author writes that as the existing reactor-based storage pools fill up, spent fuel management is becoming a hot political issue. South Korea’s nuclear utility reports that over the next 10 years, the country will face a crisis in terms of on-site storage at all four of its nuclear power plant sites. As revealed in the nuclear disaster at Japan’s Fukushima nuclear power plants in March 2011, the vulnerability of spent-fuel storage pools is a matter of serious concern. The author explores ways in which South Korea can move forward. [ABSTRACT FROM PUBLISHER]

Most of in-situ stress data in the Australian continent comes from wellbore stress analysis in deep hydrocarbon reservoirs, and earthquake focal mechanism solutions near the Australian plate boundaries, where geophysical tools facilitate understanding of the present-day stress patterns. This resulted in a paucity of stress information in many other regions such as the northern Bowen Basin, which is an active mining province, but with low seismicity rates and limited deep petroleum exploration. The mining industry runs several hundred kilometres of image logs annually to characterise geotechnical attributes. These logs provide an image from the borehole wall, which facilitates analysis of stress-related borehole deformations for in-situ stress characterisation. This paper examines the orientation of horizontal in-situ stress using different types of image logs in mine boreholes across the northern Bowen Basin. Analyses of 128 km of image logs in 680 vertical boreholes resulted in the interpretation of 9046 pairs of stress-related indicators including 735 drilling induced fractures and 8311 borehole breakouts. Our comprehensive database comprises 890 quality-ranked data records for the orientation of maximum horizontal stress (S Hmax), which makes the Bowen Basin as a basin with the highest data density in the world in terms of quality-ranked stress information according to the World Stress Map. Statistical analysis of S Hmax orientation reveals that the mean S Hmax orientation in northern Bowen Basin is N018° ± 16°. The results show that this orientation is consistent over long distances, which is in contrast with several eastern Australian basins. This uniform stress pattern agrees well with plate-scale geomechanical model predictions, which further highlights the impact of plate boundary forces in the contemporary stress pattern of this region. Detailed image log investigation did not show any systematic rotation of stress; however, some small-scale stress perturbations were observed in the vicinity of sharp stiffness contrasts and geological structures. • The most comprehensive quality-ranked basin-wide stress map in the world according to the World Stress Map database. • High-resolution stress mapping using mine borehole data. • Regional uniform stress pattern and localized (wellbore scale) stress perturbations near major geological structures. • Analysis of stress orientation versus depth. [ABSTRACT FROM AUTHOR]

Acoustic experiments on the propagation of guided waves along water-filled boreholes in water-saturated porous materials are reported. The experiments were conducted using a shock tube technique. An acoustic funnel structure was placed inside the tube just above the sample in order to enhance the excitation of the surface modes. A fast Fourier transform-Prony-spectral ratio method is implemented to transform the data from the time-space domain to the frequency-wave-number domain. Frequency-dependent phase velocities and attenuation coefficients were measured using this technique. The results for a Berea sandstone material show a clear excitation of the fundamental surface mode, the pseudo-Stoneley wave. The comparison of the experimental results with numerical predictions based on Biot’s theory of poromechanics [J. Acoust. Soc. Am. 28, 168 (1956)], shows that the oscillating fluid flow at the borehole wall is the dominant loss mechanism governing the pseudo-Stoneley wave and it is properly described by the Biot’s model at frequencies below 40 kHz. At higher frequencies, a systematic underestimation of the theoretical predictions is found, which can be attributed to the existence of other losses mechanisms neglected in the Biot formulation. Higher-order guided modes associated with the compressional wave in the porous formation and the cylindrical geometry of the shock tube were excited, and detailed information was obtained on the frequency-dependent phase velocity and attenuation in highly porous and permeable materials. The measured attenuation of the guided wave associated with the compressional wave reveals the presence of regular oscillatory patterns that can be attributed to radial resonances. This oscillatory behavior is also numerically predicted, although the measured attenuation values are one order of magnitude higher than the corresponding theoretical values. The phase velocities of the higher-order modes are generally well predicted by theory. [ABSTRACT FROM AUTHOR]

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To solve the problems in blasting roof-cutting related to pressure-relief entry retaining mining, a liquid directional roof-cutting technology is proposed in this article. To verify the adaptability of liquid directional roof-cutting technology in the practice of pressure-relief entry retaining mining, a lab cutting test was performed. The effects of the four main cutting parameters (type of abrasive, pump station pressure, speed of cutting head, nozzle diameter) on cutting capacity were examined through the test, and the optimal cutting parameters thatmeet the design requirements were ultimately identified. Based on the above test parameters, field engineering test equipment was developed. The results of a hole mouth cutting test and single-hole unilateral cutting test show that the liquid directional roof-cutting technology can be used to complete field cutting work, and the cutting depth and directional function can meet the design requirements. However, some new problems were found in the field application. For example, in the process of multihole bilateral cutting, the rock mass between four holes cannot form a cut-through face. However, these problems can be addressed by increasing the cutting capacity and optimizing the seamdirection. In summary, the design idea of conducting roof directional cutting by using liquid directional cutting technology is viable, and the proposed technology is expected to replace blasting work in several engineering applications requiring pressure relief, such as impact pressure control and coal and gas outburst control. [ABSTRACT FROM AUTHOR]

Highlights • A transfer coefficient ratio was defined as the conversion node of gas transport. • The influence of various factors on the evolution of stage characteristic was analyzed. • The transfer coefficient ratio was used to analyze the best distance of borehole. Abstract Diffusion and seepage play a significant role in the mine gas extraction, while their influence degree is dynamic with the change of time or location, showing a notable dynamic stage characteristic. Therefore, it is significant to master the conversion node of gas transport for improving the gas production. However, it is difficult to determine the conversion node and master controlling roles during mine gas extraction due to the lack of judgment index. In this work, a dual-porosity model was constructed to describe the gas transport in coal seam. Then, a transfer coefficient ratio between gas diffusion and gas seepage was used to define as the conversion node. Furthermore, our model was validated by comparing with the previous model, showing that our model can better describe the evolution of gas pressure under different stress conditions. The influence of stress, initial permeability and initial diffusion coefficient on the conversion node were investigated. Results showed that the initial permeability shows the most notable influence on the conversion node, followed by the stress. The initial diffusion coefficient has the relatively complex effect on the conversion node depending on the specific reservoir conditions. Finally, the transfer coefficient ratio was used to determine the best distance of boreholes for improving the gas production. The research results are important for CBM and mine gas extraction. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 3D AMT model from full impedance over Greenstone belt. • Regional geology is delineated. • Results in agreement with borehole and ERT section. • Delineated conductors have evidences of sulphide mineralization, which host gold. • Petrophysical characterization. Abstract The 2.1-Ga-old Paleoproterozoic Dhanjori Group of rocks covers 800 sq. km area within the Singhbhum Crustal province of eastern India, and is composed of siliciclastic metasedimentary sequence interlayered with mafic to ultramafic rocks. The meta-volcanosedimentary sequence is deformed and is of low-grade greenschist metamorphic facies. The gold occurrences within the study area are confined to the sulphide hosted mafic/ultramafic volcanic rocks and also in the basal quartz pebble conglomerates (QPC) within the Dhanjori Formation. Gold mineralization within the mafic/ultramafic meta-volcanics formations occurs within the quartz ± carbonate vein i.e. lode gold and as detrital gold within the QPC (0.5−7 ppm) of Phuljhari Formations. Regional Audio Magnetotelluric (AMT) measurements across the geological domains of Dhanjori Group and Iron Ore Group (IOG) were carried out in the frequency range of 10 kHz–10 Hz. This work discusses the conductivity model from 3-D inversion along with geology and petrophysical properties in mapping the regional geological features, associated sulphide mineralization and influence of texture, grain and bulk properties on mineralization. Dimensionality and strike analysis of the AMT data indicate complex conductivity structures. 3-D inversion of off-diagonal component of impedance was performed for obtaining an optimum value of uniform half space initial resistivity and error floor for off-diagonal component of impedance data. These were used to perform 3-D inversion of full impedance to produce a conductivity model of the study area. The conductivity model delineated major geological boundaries and the sulphide bearing mineralized zone. A major conductor is observed which extends to a depth of ∼250 m within meta-volcanics. On comparison with the available borehole adjacent to this, it is confirmed that the conductor corresponds to sulphide mineralization. The resistivity low at a depth of 150 m coincides with metabasalts (pyrite present which extends to 159 m with arsenopyrite). Another mineralized zone is observed at the boundary of iron ore group volcanics and Proterozoic-gabbro-anorthosite-ultramafics (PGAU), it starts appearing from a depth of ∼400 m and can be seen which extends to a depth of ∼800 m. It is worth mentioning that there lies Kundarkocha gold mine in the same geological domain. In addition, near surface conductor to a maximum depth of ∼50 m is observed all along the AMT profile. The sediments and fluids could account for this conducting feature. This is in agreement with available Electrical Resistivity Tomography section. The borehole within Dhanjori Volcanics also detected sulphide mineralization for ∼50 m. Thus, it can be inferred that the near surface conductor indicates the presence of gold in association with other sulphide minerals. The petrophysical studies helped to estimate the concentration of minerals within the rocks. High density and low susceptibilities in the area is an indicative of low-grade metamorphism and low level of serpentenization. Combined density and susceptibility scatter diagram and component proportion phase diagram suggests 20 vol%, 78 vol% and 2 vol% of haematite/sulphides, barren rocks and magnetite respectively. The high value of chargeability and negligible value of susceptibility indicates the presence of disseminated sulphides rather than haematites and/or massive sulphides in the rocks. Ternary plot suggest that the mineralization is controlled by texture and grain properties. Petrophysical analysis suggests that the lithotypes of the study area are similar to those of greenstone terrain in the Abitibi Subprovince. Integrating inverted section, geology and petrophysical properties has a substantial impact on the study area in terms of predicting the mineralization prospect and at the same time substantially reduces the drilling cost. Thus, the study provides a new orientation and advancement to the exploration strategy for deeper deposits. [ABSTRACT FROM AUTHOR]

Highlights • Assess Frequency and risk of human intrusion into a geological repository. • Consider a time-dependent drilling probability in a new model for resource exploration. • Human intrusion becomes vigorous for demands of resource explorations in the long-term. • Human intrusion is mitigated by enforcement of regulation and continuous knowledge during early time. • Reduced average radiotoxicity is effective to diminish the risk than reduced volume. Abstract Inadvertent human intrusion into a geological repository for radioactive waste is an incident of low frequency but high consequence. Until now, many studies have considered the frequency of deep borehole drilling for resource explorations in the site of the repository as a time-independent variable. However, future activities and technology of the human race will not be the same as today. Therefore, this study develops a new Markov chain model to estimate the frequency of human intrusion using time-dependent drilling frequencies based on the statistics of oil and gas exploration worldwide. The results showed that the frequency of human intrusion during the early time period is substantially reduced. After a few hundred years, the frequency steadily increases and approaches the value of the time-independent model. The low frequency during the early time period is attributed to enforcement of regulation, continuous knowledge of repository, and low utility of repository area. As these effects disappear, the frequency rapidly increases due to the future demand of resource exploration, which is a significant factor in increasing the risk of human intrusion. In addition, the reduction of average radiotoxicity in final waste is effective in reducing the risk, while the reduction of waste volume is insignificant for the frequency of human intrusion in the long-term. [ABSTRACT FROM AUTHOR]

A total 1357 items of in-situ stress measurement data in Chinese underground coal mines were collected, which include the data obtained by hydraulic fracturing method with small borehole applied by Mining Branch, China Coal Research Institute, and those from overcoring and hydraulic fracturing methods by other companies and organizations. The in-situ stress database of Chinese underground coal mines was established on the basis of those data, and the in-situ stress map for Chinese underground coal mines was drawn. The in-situ stress distribution features and its affecting factors were studied. The achievements are as follows:(1) the buried depth of measurement sites is an important fac-tor affecting the in-situ stresses in underground coal mines. In general, the vertical stress increases with depth, as some discreteness of stress data exists. The maximum and minimum horizontal principal stresses also increase with depth, however, the discreteness of stress data is obviously greater than that of vertical stresses, and the increasing rate of horizontal stresses with depth is smaller than that of vertical stresses. (2) The stress regime is mainly thrust type(σH> σh> σV) in shallow coal mine, and normal type(σV> σH> σh) in coal mine with depth more than 1 000 m, while it is mainly slip type(σH> σV> σh) with depth in between. (3) The ratios of horizontal stresses to vertical stresses, including those of maximum, minimum and average horizontal principal stresses to vertical stresses, the difference between the maximum and minimum horizontal principal stresses to vertical stresses, distribute in a broad range with a greater discreteness when depth is shallow. As the depth increases, the discreteness of these ratios gradually decreases with a tendency to approach constant values. (4) The stress statistical results of four strata with different lithology, that is siltstone, fine sandstone, mud sandstone and mudstone, point out that, in general, the larger the rock strength, the higher the horizontal stresses the rocks bear. (5) The rocks with higher elastic modulus bear larger horizontal stresses. However, the soft and fractured rocks with lower elastic modulus bear less horizontal stresses. [ABSTRACT FROM AUTHOR]

An alluvial plain of about 25 km2 is situated on the upper segment of the Lăpuş River between Târgu Lăpuş town and Răzoare, Borcut and Dumbrăviţa villages. It covers a tectono-erosive basin, which was formed and evolved under tectonic forces, i.e. by the movement of blocks of the pre-Quaternary basement. Based on the results of previous morphological, geological and geophysical research and the recently performed sampling and analytical data, the character and the amplitude of these movements, as well as the environmental evolution of the site, from the beginning of Late Pleistocene until present days, can be determined. For this purpose, apart from previous borehole and mining data, the grain size distribution, the palynological content and the geochemical analysis of the sediments from shallow boreholes were processed. In this case, the heavy metal content of the samples originated from the hydrothermal ore bodies of Băiuţ area were used as "markers" in the sediment columns. [ABSTRACT FROM AUTHOR]

Underground coal fires are disasters associated with coal mining activities. This study, attempts to investigate the impact of coal fires on the soil and atmosphere by measuring heavy metal concentration and borehole gas emissions for the Daquanhu coal fire zone. Different methods and equipment were used in this study, such as remote sensing, determination of the surface temperature and vegetation, field meteorological surveys, air/smoke analysis, flame photometry, atomic absorption spectrophotometry, atomic fluorescence spectrophotometry, and alkali diffusion. The results show that the surface temperature of the Daquanhu coal fire zone was reduced with a progress in coal fire extinction since 2015. Surface vegetation grew better in 2016 than in other years. The mercury (Hg) content in the western part of the fire zone is much higher than that in other parts of the fire zone. The arsenic (As) content in the eastern part is much higher than that of other parts. Data show that the estimated total amount of gas emissions during fire extinction is ~31,500 kg for CO, 489 kg for SO 2 , 12,885 kg for NO, 576 kg for NO 2 , and 20,295 kg for NOx. The intensity of the gas emissions during extinction is notably higher than that before extinction. The results also indicate coal fire's potential risk to adjacent communities, especially the risks associated with borehole injection of large amounts of possible harmful slurry, which needs to be taken seriously. [ABSTRACT FROM AUTHOR]

Analyses of borehole temperature profiles provide useful information about regional climate change over a few centuries. Data from 146 borehole sites in the crystalline terrain of peninsular India were used to reconstruct surface ground temperature history. Depths of the boreholes ranged from 150 to 1522 m. The temperature profiles were characteristic of heat flow by conduction, being largely unaffected by perturbations due to groundwater flow. The profiles show temperature anomalies in the top few hundred metres that is consistent with changing surface temperature over the past two-three centuries. Analysis of individual profiles for a ramp change in temperature reveals predominant surface ground warming in peninsular India with a mean magnitude of 1.0 ± 0.2°C for 129 ± 18 years at 95% confidence level corresponding to onset ca 1860 AD for the change. [ABSTRACT FROM AUTHOR]

Expedition 364 was a joint IODP and ICDP mission-specific platform (MSP) expedition to explore the Chicxulub impact crater buried below the surface of the Yucatán continental shelf seafloor. In April and May 2016, this expedition drilled a single borehole at Site M0077 into the crater's peak ring. Excellent quality cores were recovered from ∼505 to ∼1335 m below seafloor (m b.s.f.), and high-resolution open hole logs were acquired between the surface and total drill depth. Downhole logs are used to image the borehole wall, measure the physical properties of rocks that surround the borehole, and assess borehole quality during drilling and coring operations. When making geological interpretations of downhole logs, it is essential to be able to distinguish between features that are geological and those that are operation-related. During Expedition 364 some drilling-induced and logging-related features were observed and include the following: effects caused by the presence of casing and metal debris in the hole, logging-tool eccentering, drilling-induced corkscrew shape of the hole, possible re-magnetization of low-coercivity grains within sedimentary rocks, markings on the borehole wall, and drilling-induced changes in the borehole diameter and trajectory. [ABSTRACT FROM AUTHOR]

Borehole methods and methods of mining using combines and ploughs will be widely used in Karaganda (Kazakhstan) in lavas and short faces. Therefore, special requirements are applied to the modelling of rock destruction processes. The results should show the possibilities of improving the strength of the tool, as well as the processes that occur under pressure on the rock. The specifics of solids fracturing by a tool are described. These processes are accompanied by the formation of a plastic wedge and a thin, curved body between surfaces of a cleaved element and destructed rock. The surfaces of dislodged elements have alternating rough and smooth areas. Such zones are formed by low-frequency acoustic radiation, which can be observed during fracturing of rock cores by a punch and optically active, organic glass with a controlled speed of crack motion. The fracturing direction is predicted along paths of principal stresses and can have poorly predictable areas in zones of isoclines convergence leading to the intersection of surfaces. The element models that extend the capabilities of research, taking into account a plastic flow of rock and drilling tool for boreholes, were developed. In these studies, there can be taken into account various factors: the structure of the rocks in the face and the scheme of their collapse behind the face, the depth of the work. This is especially important for lavas and short faces. The use of 2-3 research methods (destruction of rock samples and other solid materials, studying stress-strain state (SSS) by optical and finite element modelling) is a prerequisite for obtaining accurate results. [ABSTRACT FROM AUTHOR]

Gradient and Mise-à-la-Masse IP/Resistivity surveys were conducted on a group of 19 boreholes in Eagle’s Nest, Eagle One magmatic sulfide deposit in northern Ontario, Canada. The surveys were conducted as a follow-up to the many drilled boreholes, some of which missed the target. The surveys were intended to map the distribution of the ore mineralization, outline the deposit hosted by mafic and ultramafic rocks and then guide the drilling of new boreholes. Joint Gradient and Mise-à-la-Masse data inversion produced 3D chargeability and conductivity models. The inverted 3D models in turn help delineate the outline of the mineralized zone, and determine the shape, size, strength and economic viability of the deposit. The Gradient array determined the direction of the mineralization with respect to the boreholes, and the Mise-à-la-Masse array examined the highly conductive subsurface bodies and their surroundings. The mapped ore zone shows close similarity to the 0.5 Cu% and 1.05 Ni% iso-surfaces that are produced from core assay result confirming the reliability of the results obtained in this study. [ABSTRACT FROM AUTHOR]