Coal Mining Exploration Research Articles

Financial warning for coal mining investments: Evidence from the fruit fly optimisation algorithm with backpropagation neural networks

Venture capital firms may be unable to withstand the high investments and risks associated with coal mining exploration due to limitations in the funding scale. Risk control capability is also a challenge for venture capital companies. Finding a balance between high-risk and high-return coal mining exploration projects is a problem that venture capital companies must face. We propose a financial risk-warning model for coal mining investment enterprises based on the fruit fly optimisation algorithm (FOA) with the backpropagation neural network (BPNN). The fusion of standardised and dimensionless sample data through factor analysis reduces the input dimension of the BPNN and improves its stability. The financial warning algorithm of the model has been effectively validated through experiments. The research results indicate that its accuracy has reached a high level of financial warning, reaching a level of 95%.

Fine characterization of interbedding sand-mudstone based on waveform indication inversion

Abstract Owing to the increasing challenges associated with coal mine exploration and development, extremely precise surveys with high-resolution images are required to support production. Conventional inversion methods cannot provide sufficiently precise images of the complex lithologies in coal measure strata. Accordingly, this study performed research in Qiyuan mining area, Shanxi Province, China, and predicted the complex lithology on the basis of facies control using waveform indication inversion and waveform indication simulation. Horizontal changes in seismic waveforms were used to reflect lithologic assemblage characteristics for facies-controlled constraints, and the vertical mapping the connection between seismic waveform and logging curves was shown. Moreover, high-resolution inversions of wave impedance and natural gamma parameters were conducted. Combined with lithologic shielding and accurate time–depth conversion, the inversions enabled the precise characterization of the lithological assemblage distribution in the study area. Our results showed that waveform indication inversion could distinguish between coal seams and limestone, whereas waveform indication simulation based on natural gamma could effectively distinguish between sandstone and mudstone. Furthermore, the horizontal resolution was improved and the vertical resolution extended to a thickness of 2–3 m. In addition, the inversion results were highly consistent with drilling results, with an error <0.1 m. Therefore, waveform indication inversion and simulation could be applied to coal mines for safe and efficient production.

Three Soil Bacterial Communities from an Archaeological Excavation Site of an Ancient Coal Mine near Bennstedt (Germany) Characterized by 16S r-RNA Sequencing

This metagenomics investigation of three closely adjacent sampling sites from an archaeological excavation of a pre-industrial coal mining exploration shaft provides detailed information on the composition of the local soil bacterial communities. The observed significant differences between the samples, reflected in the 16S r-RNA analyses, were consistent with the archaeologically observed situation distinguishing the coal seam, the rapidly deposited bright sediment inside an exploration shaft, and the topsoil sediment. In general, the soils were characterized by a dominance of Proteobacteria, Actinobacteria, Acidobacteria, and Archaea, whereas the coal seam was characterized by the highest proportion of Proteobacteria; the topsoil was characterized by very high proportions of Archaea—in particular, Nitrosotaleaceae—and Acidobacteria, mainly of Subgroup 2. Interestingly, the samples of the fast-deposited bright sediment showed a rank function of OTU abundances with disproportional values in the lower abundance range. This could be interpreted as a reflection of the rapid redeposition of soil material during the refilling of the exploration shaft in the composition of the soil bacterial community. This interpretation is supported by the observation of a comparatively high proportion of reads relating to bacteria known to be alkaliphilic in this soil material. In summary, these investigations confirm that metagenomic analyses of soil material from archaeological excavations can provide valuable information about the local soil bacterial communities and the historical human impacts on them.

An Innovative Directional Blasting Technique for Coal Mine Exploration and Engineering Testing

Blasting is a key method of controlling large-area hanging roofs and strong mine pressure in coal mine. The crack propagation direction after blasting has a decisive influence on control effect, and the existing blasting techniques have poor directionality, making it difficult to form a continuous, precise crack. A compound blasting technique (CBT) was proposed; this could achieve a precision, directional crack by using the combination of perforating bullet and explosives, with perforating bullet detonation first and then explosive blasting. The principle of directional crack formation by CBT was studied and a complete set of equipment was introduced, and the effect of continuous directional crack forming was studied experimentally. A CBT test was conducted in Tashan coal mine (Datong mining area): the results showed that a single crack surface was formed in the borehole after the compound blasting, which indicated the desired blasting effect. The CBT improves the accuracy and controllability of fractures and realizes precise directional control of rock strata.

Discussion on the Application Mode of Electrical Exploration in Coal Mine Exploration

Discussion on the Application Mode of Electrical Exploration in Coal Mine Exploration

Dual-Frequency Induction Polarization Electric Field Focusing Based on Intelligent Algorithm for Coal Mine Electric Exploration

As the most important and dangerous front-end production link, coal mining operations will inevitably face geological disasters such as water inrush, rock burst, collapse, and fire, posing a great threat to the life and safety of miners. Among the five major geological disasters (gas, dust, water, fire, roof) in coal mines, the threat of flooding is very serious and it is one of the main disasters in coal mines. The research and development of dual-frequency excitation technology and its application in coal mine exploration have realized the elimination of potential safety hazards, improved the work efficiency and safety factor of prospectors, and realized the automated operation of the exploration process. This article explores the electric field of the intelligent algorithm’s focused dual-frequency induced polarization method in coal mine electrical exploration, and summarizes some of the advantages of the intelligent algorithm’s focused dual-frequency induced polarization method in coal mine surveying on related materials, and then conducts related experiment, through the experiment of focusing on the dual-frequency IP method in the coal mine survey, obtained the result, in the abnormal point detection experiment, the change trend of the two curves is the same, the increase is more obvious at 1.3-1.5m, and at 1.5m When reaching the limit value, when it exceeds 1.5m, it starts to fall. It shows that when there is a water-bearing anomalous body directly in front of the tunneling section, the measurement results of the two survey lines are roughly the same. Compared with the no anomaly body, the apparent resistivity and the apparent amplitude frequency both change significantly, and reach the extreme in a certain direction. However, the actual anomalous body is located 1.0m directly in front of the tunneling section, which means that the actual position of the anomaly cannot be determined based on the apparent resistivity and the extreme point position of the apparent amplitude frequency.

Estabelecimento de valores de background geoquímico de parâmetros relacionados a contaminação por carvão

A cidade de Criciúma foi impactada por décadas de exploração de carvão e deposição de rejeitos de forma inadequada. Estas atividades interferem diretamente sobre os sistemas naturais, ocasionando a contaminação dos recursos hídricos subterrâneos e superficiais por meio de drenagem ácida de mina (DAM). A definição de valores de background geoquímico é uma estratégia para quantificar e qualificar o impacto das atividades de mineração sobre os recursos naturais. O presente trabalho objetivou estabelecer valores de background geoquímico na água subterrânea oriunda de nascentes distribuídas no município de Criciúma/SC. Os dados de qualidade de água foram avaliados utilizando-se dos métodos EDA (Exploratory Data Analysis) e de representação de frequências cumulativas. Desta forma, o trabalho permitiu determinar os valores de background para os parâmetros analíticos pH, Ferro, Manganês e Sulfato, quando ficou atestado que valores para pH encontrados dentro do intervalo que vai de 5,5 a 7,9 podem ser considerados naturais para as águas subterrâneas. Ferro e manganês apresentaram concentrações superiores de background de 2,58 e 0,30mg/L respectivamente, já sulfato apresentou concentrações entre 2,0 e 20,0mg/L. O background em muitos casos pode naturalmente suplantar limites legalmente regulamentados, fato este observado neste estudo para o manganês, que apresenta concentração de background três vezes maior que o preconizado pelo Portaria MS n. 5/2017 que trata de potabilidade de água.

A Review of Electrical and Electromagnetic Methods for Coal Mine Exploration in China

During the past 20 years, due to the rapid development of China’s economy, the amount of coal mining activities has rapidly increased, which has led to a large increase in the number of mined-out areas. Therefore, the role of geophysical exploration in coal fields has changed from the detection of coal resources to engineering geological environmental investigation. The safety, efficiency, and green production of coal mines require more advanced geophysical detection technologies. In particular, the accurate detections of the locations of water-rich mined-out areas, as well as concealed water diversion channels, have become the main focuses of coal electrical methods in recent years. Therefore, electromagnetic methods have become the main means of hydrogeological investigations and deep explorations in mine-out coal areas. In this study, a common DC method was briefly introduced, along with an induced polarization method. Then, three representative electromagnetic sounding methods, including a surface frequency-domain electromagnetic method, time-domain electromagnetic method, surface to air electromagnetic method, and mine electromagnetic method, were respectively introduced.

Nanoscale rock mechanical property changes in heterogeneous coal after water adsorption

Rock mechanical properties are of key importance in coal mining exploration, coal bed methane production and CO2 storage in deep unmineable coal seams; accurate data is required so that geohazards (e.g. layer collapse or methane/CO2 leakage) can be avoided. In this context it is well established that coal matrix swelling due to water adsorption significantly changes the coal microstructure. However, how water adsorption and the associated with microstructural changes affect the mechanical properties is only poorly understood, despite the fact that micro-scale mechanical properties determine the overall geo-mechanical response as failure initiates at the weakest point. Thus, we measured nanoscale rock mechanical properties via nanoindentation tests and compared the results with traditional acoustic methods on heterogeneous medium rank coal samples in both dry and brine saturated conditions. The microscale heterogeneity of the rock mechanical properties was mapped and compared with the morphology of the sample (measured by SEM and microCT). While the nanoindentation tests measured decreasing indentation moduli after water adsorption (−60% to −66%), the traditional acoustic tests measured an increase (+17%). We concluded that acoustic tests failed to capture the accurate rock mechanical properties changes for the heterogeneous coal during water adsorption. It is thus necessary to measure the coal rock mechanical properties at the microscale to obtain more accurate data and reduce the risk of geohazards.

Nanoscale geomechanical properties of Western Australian coal

Geomechanical properties are of great importance in coal mining exploration, (enhanced) coal bed methane production and carbon geosequestration in deep unmineable coal seams. However, coal highly heterogeneous rocks, and conventional experimental methods (e.g. acoustic, seismic or unconfined compressive strength tests) only measure the cm-m scale bulk properties. Thus, we measured the geomechanical properties at nanoscale of Western Australian Collie coal. We mapped the nanoscale mechanical heterogeneity and correlated it with the sample's morphology (measured by SEM-EDS). It was found that the quartz and siderite in the coal had higher Young's moduli (up to 28.6 GPa), while the organic coal matrix had lower Young's moduli (from 3 GPa to 5 GPa), while the soft material kaolinite had the lowest Young's moduli (<3 GPa). We conclude that it is necessary to measure the geomechanical coal properties at nano/micro scale reliably assess and eventually facilitate field scale CBM/ECBM or CO2 storage.

In-situ coal seam and overburden permeability characterization combining downhole flow meter and temperature logs.

Abstract The planning and design of any coal mine development requires among others a thorough investigation of the geological, geotechnical and hydrogeological subsurface conditions. As part of a coal mine exploration program we conducted heat pulse vertical flow meter testing. The flow data were combined with absolute and differential temperature logging data to gain information about the hydraulic characteristics of two different coal seams and their over- and interburden. For the strata that were localised based on geophysical logging data including density, gamma ray and resistivity hydraulic properties were quantified. We demonstrate that the temperature log response complements the flow meter log response. A coupling of both methods is therefore recommended to get an insight into the hydraulic conditions in a coal seam and its overburden.

An Application of Ecological Compensation Mechanism Framework: A Case for Yulin County

In this paper, framework of eco-compensation mechanism has been mapped by using principle of system engineering and "layer-by-layer decomposition", combining with the resource of documents and data. Combining with eco-environmental compensation of Yulin coal mining exploration areas, this system framework can be decomposed and its process and mechanism of action can be imitated. Then a general conclusion will be drawn. All that will provide a theoretical basis for our government departments to develop policies of ecological compensation for coal resource exploration areas.

Analysis of the Strength and Reliability of Hydraulic Support with Finite Element Method

Hydraulic support is one of the most important equipments of coal mine exploration， this thesis is to analyse hydraulic support strength and reliability with finite element method. With the example of ZF8000/22/35 hydraulic support, this paper uses the HyperWorks finite element software to analyse the strength of the hydraulic support, and then, with the ANSYS, this paper calculates the reliability of the hydraulic support and figures out the sensitivity of the hydraulic support. Finally, some methods of reliability analysis with finite element method are summarized,these methods can give reference to the design of hydraulic support.

Sub-basalt coal seam structure imaging - results from numerical modelling

Tertiary volcanic basalts (high velocity layers) exist in both the Bowen and Sydney Basins of Eastern Australia. The use of conventional seismic for coal mine planning is often compromised and produces sub-surface images of variable quality because the wave propagation through these heterogeneous basalt layers becomes complex. The difficulty of exploring beneath the Tertiary volcanics makes these areas less attractive for coal mining exploration. Workers involved in sub-basalt imaging in the petroleum sector, mainly give the following reasons for the difficulties in imaging beneath high-speed surface layers: 1. The strong impendance contrast between the basalts and the underlying sedimentary rocks prevents the penetration of seismic energy into target zones (Fruehn et al., 1998; Behera, 2006). 2. The roughness of the basalt boundaries causes significant disruption and scattering of the transmitted wavefield (Behera, 2006). 3. The scattering of heterogeneity of the basalt (Ziolkowski et al., 2001; Hobbs, 2002). To improve seismic imaging in these cases, modifications to data acquisition and data processing procedures which improve data quality and increase S/N were proposed (Fliedner and White, 1999; Hu et al., 2003). Commonly used techniques involve long offset, low frequency and converted wave data acquisition (Ryu, 1997; Wombell et al., 1999; Hanssen et al., 2003; Lau et al., 2007; Spitzer et al., 2008). In data processing, procedures such as pre-stack depth migration, have improved the quality of sub-basalt images (Fruehn et al., 1999; Reshef et al., 2003; Gallagher and Dromgoole, 2008). Wave-equation modelling techniques have also been used to investigate the influence of high speed layers on seismic wave propagation (Battig and Hearn, 2001; Hanssen et al., 2003). In this paper, we use a 2D finite-difference-based full elastic wave-equation forward modelling algorithm to further investigate the effects and characteristics of seismic wave propagation under different basalt settings. Our objective is to provide some insights into the seismic wave propagation and guidance for improving the quality of seismic sections for coal mine investigations.

A Rock Mass Assessment Procedure Based on Quantitative Geophysical Log Analysis of Coal Measure Sequences

Geophysical logging is routinely undertaken as part of most coal mine exploration programs. Currently, the main application for the logs is to determine coal seam depth and to qualitatively estimate coal quality, lithology, and rock strength. However, further information can be obtained, if quantitative log interpretation is made.To assist in the uptake of quantitative interpretation, we discuss log responses in terms of the mineralogy of the clastic sedimentary rocks frequently found in the Australian black coal mining areas of the Sydney and Bowen Basins. We find that the log responses can be tied to the mineralogy with reasonable confidence. Ambiguities in the interpretation will be better resolved if a full suite of logs is run. A method for checking for internal consistency, by comparing calculated and observed velocities, is also described.A key driver for quantitative interpretation is geotechnical characterisation. We propose a classification system for clastic rocks that takes into consideration physical rock properties that can be inferred from geophysical logs.

Quantitative geophysical log analysis in coal measure sequences

Geophysical logging is routinely undertaken as part of coal mine exploration programs. With minimal analysis, coal seam depth can be determined and estimates made of coal quality, lithology and rock strength. Quantitative log interpretation will add to this information. We discuss log responses in terms of the mineralogy of the clastic sedimentary rocks frequently found in the black coal mining areas of the Sydney and Bowen Basins. We find that the log responses can be tied to the mineralogy with reasonable confidence. If a full suite of logs is run, ambiguities in the interpretation may be resolved. A key driver in this work is geotechnical characterisation. With this additional geophysical input, it should be possible to develop improved rock mass classification schemes.

3D seismic surveying for coal mine applications at Appin Colliery, NSW

Modern underground coal mining requires detailed knowledge of geological faults and other geological features. A fault of throw greater than a seam thickness of about 3 m can cause enormous delays to mine production. BHP Coal has been using 2D seismic surveying for some time to map structures with throws down to about 5 or 6 m but in an effort to obtain better resolution (mainly through seismic coverage), 3D seismic surveys are now being undertaken.For this application, the strength of 3D seismic surveying lies in the ability to establish the continuity of subtle features from one bin section to the next. Maps of the interpreted horizons allow very small features to be seen. Attribute analysis adds further structural and lithological information to the interpretation.The present indications are that 3D seismic surveying is set to become a key tool in coal mine exploration.

Geophysics at the Coal-Face

Coal is a low-cost commodity and coal miners profit margins are slim, such that mining companies must maintain tight cost control to achieve acceptable returns. The challenge to coal geophysics is to adapt to these economic constraints and provide cost-effective, reliable methods for exploration and mining requirements. The geophysical methods which have been used in the reconnaissance, pre-development, and operational stages of coal exploration and mining are reviewed in terms of their exploratory function and their typical frequency of application. Borehole logging is the one method which is highly utilised for both surface and underground coal mining exploration, although seismic methods (mainly high-resolution reflection, and in-seam), are also frequently applied in underground coal-mining investigations. Because surface coal mining is constrained to shallow seams, most exploration is achieved by drilling methods, with geophysics playing a supporting but subordinate role. Also surface mining is less sensitive to seam disturbances such as faulting, rolls and intrusions, and can afford to set less strict requirements for prediction and resolution. The trend in underground mining is towards high-production longwall methods, which are much less tolerant of disturbance, and demand survey reliability and resolution standards which often stretch the limits of current exploration technology. A Workshop on Underground Coal Mining Exploration Techniques was conducted by the Australian Coal Association in 1991 to identify the strategies and priorities for future research and development. Most of the recommendations coming from the Workshop incorporated geophysical technologies, particularly the development of borehole logging methods which can be applied to in-seam drillholes. The recommendations also identified the need to selectively import and adapt analogous but more advanced technology from other areas, such as seismic reflection expertise from the petroleum industry, and to consolidate on the promising beginnings shown by techniques such as the radio-imaging method and in-seam seismic. The future also holds opportunities for geophysics to assist in the development and application of innovative mining systems. High-wall mining, continuous surface miners, and the increasing trend towards high-production automated mining equipment, bring with them the need to provide geophysical monitoring sensors and guidance systems.

Role of seismic surveying in coal mining exploration : Goossens, R F; Buchanan, D J Min Sci TechnolV1, N4, Aug 1984, P253–267

Role of seismic surveying in coal mining exploration : Goossens, R F; Buchanan, D J Min Sci TechnolV1, N4, Aug 1984, P253–267

Role of seismic surveying in coal mining exploration : Goossens, R F; Buchanan, D J Min Sci TechnolV1, N4, Aug 1984, P253–267

Role of seismic surveying in coal mining exploration : Goossens, R F; Buchanan, D J Min Sci TechnolV1, N4, Aug 1984, P253–267