Mine Pressure Research Articles

Mechanical Analysis of Weakly Cemented Roof of Gob-side Entry Retaining in Fully-Mechanized Top Coal Caving Mining

To investigate the mine pressure behavior of weakly cemented roof of gob-side entry retaining (GER) in fully-mechanized top coal caving mining, the structural characteristics of lateral immediate roof in 4-1101 working face of Awuzisu Coal Mine were studied by using of numerical simulation, theoretical analysis and in-site measurement. Mechanical model of “equivalent block” composite structure of immediate roof was established, and verified by field test. The results indicate that weakly cemented roof has a large caving range, and it is easy to form the “equivalent block” composite structure in mechanized top caving mining. This structure affects roof breaking, and provide vertical constraint to the roof of GER. It explains the phenomenon that, the roof pressure of GER increases with the advancing of the working face, but the growth rate decreases gradually before the main roof breaking. This research can provide reference to roadside support design and surrounding rock control of GER with weakly cemented roof.

Experimental study on the control effect of ground stress on the damage of coal seam mining floor

In order to study on mechanism of in-situ stress control on the coal floor damage during deep coal seam mining, the internal relationship among ground stress, mine pressure and floor water inrush was analyzed base on the increasing distribution rule of ground stress with the increasing depth of stratum. It is shown that the stress on the deep coal seam has obvious control effect on the depth of the floor damage and failure through the experimental study and the statistical analysis of the measured data of the mining damage depth of the coal seam floor. And the calculation formula for the depth of the floor failure in the deep seam mining was put forward.

The characteristics of mining induced stress fluctuations in broken rock mass over one kilometer deep coal mine

Mine pressure is critical to the safety of working face. Evaluating the working resistance accurately of the stope hydraulic supports is one of the most effective and direct ways to reflect the overall stress characteristics of the roof and the defor?mation, movement and destruction of overlying strata. Due to the complex breaking form of the roof, the working resistance of the hydraulic supports at different positions of the mining face varies in different ways. One can obtain the pressure of hydraulic support system by pressure monitoring and analyze its fractal characteristics. Through spectrum analysis, a new parameter called accumulation power spectral density is defined which is used to describe the difference of working resistance of stope hydraulic supports. The results show that the fractal dimensions of face-end supports are smaller and face-end supports are unco-ordinated. Through in-situ monitoring, it is found that the mining stress has unstable periodic fluctuation characteristics. The conclusion can provide reference for rational selection and optimization of the similar-mining lay-outs.

Research on Physical Similarity Simulation of Mining Uphill and Downhill at the Large‐Angle Working Face

With the development of coal mining and the continuous expansion of mining intensity, large dip angle comprehensive mechanized coal mining as an important development direction and goal has become a worldwide research topic in the coal industry. The working face faces many production problems that need to be solved, such as the large‐angle downhill mining, the large‐angle uphill mining, and other complicated geological conditions (such as skew, anticline, and fault). In view of the above problems, with the specific conditions of Xinji No. 2 Mine, through the physical similarity simulation, the research on the roof movement law of the fully mechanized mining face under the mining conditions of large dip angle (depression angle and elevation angle are more than 40° and 20°, respectively) is studied. The distribution law of abutment pressure, movement law, and distribution range of water‐conducting fracture zone after mining are emphasized. Meanwhile, the paper analyzes and compares the related mining pressure law of inclined longwall fully mechanized mining face under general conditions, forming a systematic, comprehensive, and scientific understanding of the law of mining pressure under such conditions. This achievement is of great significance to the prevention and control of water, support design, safety production, environmental improvement, improvement of enterprise efficiency, and advancement of coal science and technology.

Study on Surrounding Rock Stability of Long-Span Coal Roadway under Influence of Mining and Support Technology Optimization

Taking stoping safety of large-span working face in a coal mine in Shanxi as the background, the damage and movement law of overlying strata structure in coal roadways under the influence of mining are studied. Combined with the actual production of the mine, the mining pressure characteristics of the working face and the influence range of mining in the working face are mastered. Main research contents and conclusions are that: (1) Numerical simulation of roadway stability is carried out using UDEC software, stimulating the stress and strain variation of surrounding rock under unsupported state. Based on this, the roadway support parameters are simulated and optimized, which provides valuable reference for practical engineering. (2) Study the simplified design process of bolt support parameters, improve the accuracy of bolt support parameters and reduce the cost of coal mine support to increase the incidence of coal mine roof accidents, providing a basis for coal mine safety production.

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ ГОРНОГО ДАВЛЕНИЯ С ПОМОЩЬЮ ИНТЕГРАЦИОННОЙ ПАЛЕТКИ

ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ ГОРНОГО ДАВЛЕНИЯ С ПОМОЩЬЮ ИНТЕГРАЦИОННОЙ ПАЛЕТКИ

Influence Law of Interbedded Strata and Their Collapse on the Mining of Extremely Thick Coal Seam under Goaf

Interbedded strata and their collapse are vital to mining pressure control for extremely thick coal seam under goaf. To ensure the stability of the support and to avoid roof collapse, some traditional underground pressure theoretical models had been widely used in the control of surrounding rock and the selection of support. However, one of the challenges for extremely thick coal seam under goaf is that the abnormal disasters, such as support crushing and water inrush that were occurring frequently. To solve this problem, the movement characteristics of overburden rocks during the mining of extremely thick coal seam under the conditions of the interlayer thickness of 5 m and 40 m were studied by using the similar simulation experiments, while the numerical simulation experiments were carried out for the interval between coal seams of 15 m and 60 m, respectively. Finally, the structure and mechanical transfer mechanism of overburden in stope under different thickness interbedded strata were analyzed dynamically, and the condition of full‐thickness connection between upper goaf and lower goaf and corresponding judgment criteria are obtained. These results can guide future research on the mechanical of extremely thick coal seam under goaf, which can provide a theoretical basis and engineering reference for similar projects.

Research on Prevention and mitigation of Deep Mine Hazards in Ningzheng Mining Area

Ningzheng Mining Area, as one of the key mining areas of Longdong Energy Base in Gansu Province, whose average overburden depth of coal seams is more than 800 meters and average thickness of coal seams ranges from 8m to 14m. This paper analyzed the typical characteristics of water damage, heat damage, high mine pressure and gas disaster in Ningzheng mining area. Disaster prevention measures and two resource utilization prevention technologies (namely EMS cooling technology, Gas power generation and cogeneration system cooling technology) were put forward, the rearch has a realistic significance for the safety exploitation, comprehensive utilization of deep coal resources in China, energy conservation and emission reduction and development of circular economy.

深埋留巷矿压的煤柱尺度特征数值模拟分析

深埋留巷矿压的煤柱尺度特征数值模拟分析

Characteristics Analysis of Roof Overburden Fracture in Thick Coal Seam in Deep Mining and Engineering Application of Super High Water Material in Backfill Mining

With the development of deep mining, the mining pressure on the working face is increasing, the failure height of thick seam roof is increasing, and the failure characteristics of roof are becoming more complex. The cracks in the overlying strata of the roof are greatly increased and activated by mining influence, which increases the impervious threat of the roof. In order to solve this problem, the failure stress model of thick coal seam roof was established; the 1308 working face of Yancheng Coal Mine was taken as the engineering background, and the FLAC3D numerical simulation software was used to simulate the formation failure process of 1308 working face with the threat of water permeability; the drilling section water injection test method was used to measure 1308 working face; High water material is used as raw material to fill 1308 working face. The results show that: (1) the failure height of overlying strata is calculated more accurately by mechanical model, and the failure characteristics are analyzed; (2) the failure height of overlying strata calculated by numerical simulation is smaller than that calculated by theory; (3) the problem of serious roof caving in thick coal seam can be effectively alleviated by filling with super-high water material.

Underground ground control monitoring and interpretation, and numerical modeling, and shield capacity design

Mine or longwall panel layout is a 3D structure with highly non-uniform stress distribution. Recognition of such fact will facilitate underground problem identification/investigation and solving by numerical modeling through proper model construction. Due to its versatility, numerical modeling is the most popular method for ground control design and problem solving. However numerical modeling results require highly experienced professionals to interpret its validity/applicability to actual mining operations due to complicated mining and geological conditions. Underground ground control monitoring is routinely performed to predict roof behavior such as weighting and weighting interval without matching observation of face mining condition while the mining pressures are being monitored, resulting in unrealistic interpretation of the obtained data on mining pressure. The importance of ground control pressure monitoring and simultaneous observation of mining and geological conditions is illustrated by an example of shield leg pressure monitoring and interpretation in an U.S. longwall coal mine: it was found that the roof strata act like a plate, not an individual block of the size of a shield dimension, as commonly assumed by all researchers and shield capacity is not a fixed property for a longwall panel or a mine or a coal seam. A new mechanism on the interaction between shield’s hydraulic leg pressure and roof strata for shield loading is proposed.

Analysis of Instability Mechanism and Support Technology of Surrounding Rock in High Stress Soft Rock Mining Roadway

Based on the on-site investigation and monitoring of the working face of Yannan Mine I0128203, by using FLAC 3D numerical simulation software, the mechanism of deformation and instability of roadway surrounding rock is analyzed, and it is concluded that the existing support method has been unsuitable for the soft rock roadway and technical requirements. Aiming at this problem, propose a new technology of hollow grouting anchor support. The support parameters and support process are optimized through field experiments. The results of mine pressure observation show that the technology has achieved the goal of maintaining roadway stability.

The mining pressure in mixed workface using a gangue backfilling and caving method

The mining pressure in mixed workface using a gangue backfilling and caving method

Using Systematic Conservation Planning to support Marine Spatial Planning and achieve marine protection targets in the transboundary Benguela Ecosystem

The Benguela Current Large Marine Ecosystem (BCLME) is subject to moderate to high levels of fishing, mining and numerous other human pressures, all of which are set to intensify through current socio-economic development initiatives in Angola, Namibia and South Africa. There is, however, minimal spatial protection of marine and coastal ecosystems in the region, potentially reducing the sustainability of the planned development and the likelihood of achieving Sustainable Development Goals. As a precursor to Marine Spatial Planning (MSP) processes in the three countries, and to guide establishment of Marine Protected Areas (MPAs), this study aimed to: assess two headline indicators of ecosystem status, namely their potential threat status and current spatial protection levels; and to use Systematic Conservation Planning (SCP) to prioritise specific areas for protection to achieve networks of MPAs that are representative of national and regional biodiversity. Two hundred and forty eight ecosystem types in the coastal (n = 134), offshore benthic (n = 86) and pelagic (n = 28) zones of the BCLME were classified, mapped and assessed. Overall, 35% of all ecosystem types in the study domain were threatened, with more threatened coastal (37%) and offshore benthic (37%) ecosystem types compared to pelagic ecosystem types (14%), although the same pattern was not necessarily evident within each country. Nearly two thirds (59%) of the BCLME ecosystem types were not protected in MPAs, and most of those that were well (19%) or moderately protected (14%) were coastal types that are within a single extensive MPA in Namibia. Notwithstanding, there was still a sufficient area of most ecosystem types that was assessed to be in good ecological condition in all three countries and that could be prioritised for representative protection of the region's biodiversity. A portfolio of priority conservation areas was identified from Marxan selection-frequency outputs, providing a spatial vision for protected areas in the BCLME that includes coastal, inshore and offshore areas in all three countries. This first assessment of marine ecosystem threat and protection status for an entire LME demonstrates a rapid science-based approach that can inform integrated ocean management and multiple development goals. The study provides a basis for identifying Ecologically or Biologically Significant Marine Areas, potential sites for MPAs or other spatial management in the region, and demonstrates the contribution of SCP and spatial management to MSP.

Study and Application of Roof Cutting Pressure Releasing Technology in Retracement Channel Roof of Halagou 12201 Working Face

The retracement channel roof cutting (RCRC) technology can change the overburden structure actively by cutting off the roof of channel along the direction of working face tendency and make use of the gangue collapsing from roof cutting range to fill the goaf and weaken the mining pressure during the retracement process of working face. In order to solve the problems of high stress in surrounding rock and serious deformation of retracement channel in Halagou coal mine, it is the first time that the pressure releasing test is carried out on the 12201 working face by the method of the directional presplitting roof cutting in retracement channel. First, according to statics theory and energy theory, the stress state of hydraulic support and roof deformation mechanism of retracement channel are analyzed. Then the roof cutting design of retracement channel is determined according to the geological conditions of 12201 working face, and the cutting effect is analyzed by numerical simulation. Finally, the field test is carried out on the 12201 working face to verify the effect of pressure releasing by roof cutting. The result shows that, with the roof cutting design including the roof cutting height being 8m and roof cutting angle being 45°, the roof subsidence of the 12201 working face retracement channel in Halagou mine is reduced to 132.5mm, and the hydraulic support resistance is maintained at 1361KN. And there is no hydraulic support crushed; the deformation of the retracement channel is also small; namely, the effect of roof cutting for pressure releasing is obvious.

An ultrasonic-based method for longwall top-coal cavability assessment

Longwall top-coal caving (LTCC) is widely employed in the underground mining of thick coal seams. The technique divides a thick coal seam into a lower and an upper section. The bottom coal is sheared by a cutting head and transported by a conveyor in front of the support while the top coal fails and caves under mining pressure, transported by a conveyor at the rear of the support. In an LTCC panel, accurate assessment of top-coal cavability is critical to the design of mining parameters required to achieve continuous caving of top coal. In the present paper, an integrated detection system in which fracture development and ultrasonic wave velocity are used to characterize top-coal cavability is introduced. The cavability is predicted conveniently due to ease of access of the ultrasonic wave velocity in the top coal. Accordingly, an ultrasonic model is established and coupled to the mechanical model previously proposed by the authors to simulate the evolution of the wave velocity in stressed coal. The mechanical-ultrasonic coupling model is validated by comparison against experimental data and further extended to evaluate top-coal cavability in Dongzhouyao mine with a finite difference type code. The predictions, including the excavation-damaged zone, roof weighting interval, stress distribution, stress rotation and ultrasonic wave velocity evolution, are consistent with the field measurements. With the proposed model, the influence provided by hydraulic fracturing on top-coal cavability is investigated by conducting the finite difference type modeling.

Mechanical Performances of Pressure Arch in Thick Bedrock during Shallow Coal Mining

Due to the periodicity of mine pressure, it can easily lead to a wide-range damage of the overburden rock under shallow coal mining conditions, and the falling of the overburden rock is usually a serious threat to the mining safety. Based on the monitoring data of mine pressure in a typical shallow coal mine in northern China, the mechanical model of the surrounding rock in the mining field was built and the identification indicators of the pressure arch after coal mining was defined. Then, the arching mechanism, the stress distribution characteristics in different positions, and the bearing capacity of the pressure arch were analysed, and the evolution characteristics of the pressure arch under shallow horizontal coal mining were verified by numerical simulation and physical experiment. Results show that there is a core-bearing zone in the pressure arch, and the width of the core zone determines the bearing capacity of the pressure arch. The evolution of the pressure arch affects the formation and development of the caving arch of the loose zone in the mining field. The conclusions obtained in the study are of important theoretical value to direct the similar engineering practice.

The Migration of Coalbed Methane under Mining Pressure and Air Injection: A Case Study in China

Gas outburst has always affected the safety of coal mining. To eliminate this risk by high-efficiency extraction of coalbed methane (CBM) in 4102 working face of number 3 coal seam in Hebi Number 3 coal mine, a model of CBM extraction in working face was established which was considering the mining impact of adjacent 4101 working face. In this model, the coupling relationships between stress, desorption, and migration of methane were analyzed. Moreover, we also studied the changes of methane pressure, plastic failure scope, and permeability of coal during the mining and then verified the results with the field data. And on this basis, a stimulation solution for methane extraction by injecting air into coal seam was presented, and the extraction effect was simulated. The simulation results show that the injection of air decreases the effective stress of coal which increases the permeability of coal and promotes the methane migration within the coal seam fractures. Besides, affected by the velocity of gas migration, the pressure drop between fractures and matrix will reduce with time while air injection can provide extra power for gas migration in fractures which causes the desorption and diffusion of methane in the matrix. So this stimulation solution can enhance the efficiency of gas extraction of coal seam and prevent gas outburst of the working face.

Study on the permeability characteristics of coal containing coalbed methane under different loading paths

AbstractDuring the degassing process of coalbed methane, the external loads could change the permeability of the coal seam by means of transient and permanent deformations, which dramatically influence the production efficiency of coalbed gas. Due to the ignorance of irreversible deformation of coal permeability, the gas extraction efficiency and the prediction of gas disaster in underlying mining need to be improved. Thus, it is better to clarify the permeability change characteristics with irreversible deformation of coal. In this paper, the influence of different loading paths on the permeability of gas‐containing coal was studied, and six loading paths were studied by employing a self‐designed triaxial cyclic loading system. The results of this study show that the permeability of gas‐containing coal samples would significantly change with different loading paths. Corresponding to the variation of mining pressure or periodic geo‐stress varying in the excavation of roadways, both an increase in the axial pressure and an increase in the confining pressure would cause a decrease in gas permeability. In addition, the permeability of gas‐containing coal would be damaged even when the external loads are removed. When given a constant strain loading, the permeability shows a “V”‐shaped change with increased strain, and the transversal point of permeability locates between the yield point and the peak intensity. Therefore, it can be concluded that external loads less than the maximum strength of coal would lead to permeability loss in the coal seam, vice versa, the permeability will be increased. Hence, research results contributes to improving the gas permeability and increasing the gas production from coalbed by imposing effective loads on original coal seams through mining speed control.

Density and distribution of a brown bear (Ursus arctos) population within the Caucasus biodiversity hotspot

Population declines and extirpations of large mammalian carnivores are major concerns for global biodiversity conservation. Many large carnivores are vulnerable to conflict with humans and attract conservation attention for their flagship appeal and ecological importance. Coexisting with carnivores requires an understanding of carnivore distribution and abundance relative to human activities and disturbances. Such knowledge is often hindered by the rare and elusive nature of carnivores and the lack of systematic ecological surveys in biodiverse regions facing high levels of threat. The Caucasus Ecoregion is one such biodiversity hotspot harboring several threatened mammal species for which there is a paucity of reliable data, including brown bears (Ursus arctos). Caucasus brown bear populations have declined significantly from historical times and may be isolated and vulnerable to disturbance from development activities such as mining, as well as increasing hunting pressure. To inform land-use planning and bear conservation in the Caucasus Ecoregion, we conducted systematic surveys in May–October 2015 in the foothills of the Caucasus Mountains within the Vayots Dzor region of Armenia. We used noninvasive genetic sampling, camera trapping, and statistical models that account for imperfect detection to estimate density and distribution of the bear population in the 1,000-km2 study area. Across 34 sampling sites, we obtained 3,163 camera-trap photos of brown bears and genotyped 28 individual bears (7 males and 21 females). Spatially explicit capture-recapture models revealed an unexpectedly high density of bears (59.4/1,000 km2; females = 44.6, 95% confidence interval, CI = 25.4–78.4; males = 14.8, 95% CI = 6.6–34.0), and multi-method occupancy models indicated that bears were distributed across most of the study area (ψ = 0.85; SE = 0.07). These results provide robust evidence that a significant population of brown bears persists in Armenia's Vayots Dzor region, despite a history of hunting and habitat loss that have driven declines in brown bear populations throughout much of the Caucasus Ecoregion. Continued persistence of this flagship species may be threatened by mining, poaching, and other anthropogenic pressures in the region, underscoring the urgent need for strategic conservation planning, impact mitigation, and expanded ecological monitoring within this biodiversity hotspot.