scholarly journals Investigation of Seepage Law in Broken Coal and Rock Mass under Different Loading and Unloading Cycles

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zihao Kan ◽  
Lei Zhang ◽  
Mingxue Li ◽  
Xiaochuan Yuan ◽  
Mengqian Huang
Keyword(s):  
Rock Mass ◽  
Loss Rate ◽  
Sensitivity Coefficient ◽  
Stress Sensitivity ◽  
Mining Operations ◽  
Exponential Relationship ◽  
Coal Particles ◽  
Loading And Unloading ◽  
Seepage Law ◽  
The Impact

In order to study the seepage law of broken coal seams affected by multiple mining operations, a cyclic loading and unloading seepage experiment was carried out. For this purpose, the seepage law of broken samples with different coal and rock ratios was analyzed. The results of our study demonstrated that the permeability of the broken samples showed a decreasing trend. After a loading and unloading cycle, the permeability was significantly reduced. The impact of the loading stage on the broken sample was higher than that of the unloading phase. When the proportion of coal particles in the mixed samples of broken coal and rock was 50%, the irreversible permeability loss rate and permeability loss rate of the samples showed the highest values. The irreversible permeability loss rate and permeability loss rate of the broken rock mass were greater than those displayed by the broken coal mass. The stress sensitivity coefficient curves of the 5 types of broken coal and rock masses presented the same changes. The stress sensitivity coefficient curve and the effective stress displayed an exponential relationship.

Rock Movement in Tectonic Zones. Mining Activities and Rock Pressure Management in the Norilsk-Kharaelakh Fault Area

2020 ◽  
pp. 148-151
Author(s):  
S.G. Kirillov ◽  
Z.G. Ufatova ◽  
I.F. Khrushchev ◽  
K.A. Bashirov
Keyword(s):  
Rock Mass ◽  
High Mobility ◽  
Mining Operations ◽  
Profile Line ◽  
Initial Stage ◽  
Tectonic Zones ◽  
Rock Movement ◽  
Hazard Level ◽  
And Control ◽  
The Impact

The article describes the rock mass state within the boundaries of the Skalistiy mining allotment. The ore mass within the mine field was found to preserve its rock-bump hazard and show high mobility in the impact zone of the Norilsk-Kharaelakh Fault and the associated high failure potential manifested as roof cavings. Based on the monitoring results along underground profile lines, it was concluded that the displacement process is currently at its initial stage. Moreover, the maximum subsidence in the central part of the profile line is about 3 times higher (up to 35 mm) than in other areas. This is caused by immediate proximity of this zone to the Norilsk-Kharaelakh Fault. Assessment of the bump hazard level of this rock mass with the help of the Prognoz-2 instrument that was performed by the rock-bump forecasting and control teams of the mine and the Norilskshakhtstroy company, showed the 'Not Hazardous' category in all cases. However, the progress of mining operations towards the Norilsk-Kharaelakh Fault may lead to deterioration in the condition of mine workings. This can be manifested through rock exfoliation from the walls of the advance workings of the safety layer in highly and extremely faulted rocks. In addition, permanent workings, which are one of the most critical structures of the production level and which will be used until the development of the deposit area adjacent to the Norilsk-Kharaelakh Fault is completed, will be maintained in increasingly difficult conditions. The article describes recommendations for mining operations in the fault area with account for the current mining and geomechanical situation and the potential for its change.

scholarly journals Numerical Simulation of Shale Gas Multiscale Seepage Mechanism-Coupled Stress Sensitivity

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Xun Yan ◽  
Jing Sun ◽  
Dehua Liu
Keyword(s):  
Shale Gas ◽  
Gas Flow ◽  
Gas Transport ◽  
Sensitivity Coefficient ◽  
Stress Sensitivity ◽  
Gas Production ◽  
Molecular Flow ◽  
Adsorption Phenomenon ◽  
Gas Seepage ◽  
The Impact

The complexity of the gas transport mechanism in microfractures and nanopores is caused by the feature of multiscale and multiphysics. Figuring out the flow mechanism is of great significance for the efficient development of shale gas. In this paper, an apparent permeability model which covers continue, slip, transition, and molecular flow and geomechanical effect was presented. Additionally, a mathematical model comprising multiscale, geomechanics, and adsorption phenomenon was proposed to characterize gas flow in the shale reservoir. The aim of this paper is to investigate some important impacts in the process of gas transportation, which includes the shale stress sensitivity, adsorption phenomenon, and reservoir porosity. The results reveal that the performance of the multistage fractured horizontal well is strongly influenced by stress sensitivity coefficient. The cumulative gas production will decrease sharply when the shale gas reservoir stress sensitivity coefficient increases. In addition, the adsorption phenomenon has an influence on shale gas seepage and sorption capacity; however, the effect of adsorption is very weak in the early gas transport period, and the impact of later will increase. Moreover, shale porosity also greatly affects the shale gas transportation.

scholarly journals Seepage Behaviour of Fractured Rock Mass Infilling Using Different Transfixion Rates under Cyclic Loading

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Shuren Wang ◽  
Jiyun Zhang ◽  
Zhichao Li ◽  
Yongqiang Yu
Keyword(s):  
Rock Mass ◽  
Cyclic Loading ◽  
Fractured Rock ◽  
Confining Pressure ◽  
Sensitivity Coefficient ◽  
Stress Sensitivity ◽  
Fractured Rock Mass ◽  
Penetration Length ◽  
Permeability Changes ◽  
Cycle Loading

It is very important to determine the seepage behaviour of fractured rock mass infilling to evaluate the stability of the surrounding rock. The joint transfixion rate is the ratio of the unpenetrated length to the penetration length of a joint in a sample. Samples of the fractured rock mass infilling using different transfixion rates were prepared, and a TCQT-III low-permeability coal-rock triaxial seepage device was used to conduct three cycles of confining pressure-seepage coupling tests. Results show that the permeability is a power function in the confining pressure of the sample, and the permeability changes most significantly with the confining pressures. The permeability of the sample increases exponentially with the joint transfixion rate. The permeability loss is positively correlated with the plastic deformation of the sample; the permeability changes most significantly during the first cycle loading. There is over 60% recovery of the permeability of the sample under cyclic loading for loads that do not exceed the strength of the infilling. The stress sensitivity coefficient decreases as the confining pressure increases and is higher during the unloading stage than that during the loading stage for samples with an incomplete transfixion rate. The conclusions obtained in this study can serve as a reference for grouting applications.

scholarly journals ASSESSMENT OF THE IMPACT OF GEOMECHANICAL PARAMETERS VARIABILITY ON UNDERGROUND EXCAVATIONS STABILITY USING RESPONSE SURFACE METHOD

2013 ◽  
Vol 35 (1) ◽  
pp. 183-194 ◽  
Author(s):  
Witold Pytel ◽  
Joanna Świtoń
Keyword(s):  
Rock Mass ◽  
Response Surface ◽  
Response Surface Method ◽  
Safety Issue ◽  
Mineral Deposit ◽  
Mining Operations ◽  
Mean Values ◽  
Surface Method ◽  
Geomechanical Parameters ◽  
The Impact

Abstract Recognition of properties of the rock mass surrounding a mineral deposit is particularly important for the mining operations at greater depths. Since the rock mass is usually not homogeneous, and its parameters have characteristics of randomness, underground workings safety issue should always be analysed taking into account the dispersion of the values of these parameters around their mean values. In order to assess the impact of geotechnical parameters uncertainty on the excavation stability one uses the appropriate statistical approach. In this paper, by analysing successive combinations of geomechanical parameters of the rock in the measured range, we examined the effect of their variability on risk of underground excavation instability using response surface method.

scholarly journals Simulation Possibilites of the Post-Mining Goafs Impact on the Deformations Induced by Next Underground Mining Operations with Use of the Cellular Automata Method

2020 ◽  
Author(s):  
Sikora Paweł
Keyword(s):  
Rock Mass ◽  
Underground Mining ◽  
Mining Area ◽  
Mining Operations ◽  
New Approach ◽  
Upper Silesian Coal Basin ◽  
Under Construction ◽  
The Impact ◽  
Further Development

Abstract Underground mining operations in the area of a rock mass affected by previous exploitation may cause additional deformations to appear on the surface. The size of these deformations can be significant, and their character is often non-linear. The nature of these deformations cannot be justified solely by the impact of current mining operations. At the same time, the predictive method of S. Knothe, widely used in Poland, does not explicitly include these types of phenomena. In the area of intensive and long-term mining exploitation, such as the Upper Silesian Coal Basin, the practical possibility of simulating this occurrence may be helpful in the planning of new mining exploitation under construction objects. Today we are usually limited to numerical modelling methods like finite difference method (FDM). This one base on the principle of mechanical similarity. The theoretical usefulness of method (and its similar) has already been proven many times. The main impediment to its practical application is the lack of recognition of the rock mass in terms of its mechanical properties. The presented method is a new approach to the possibility of modelling the subject phenomenon. The method has not been used in practical forecasting mining area deformation caused by underground deposits mining. It’s characterized by a huge potential for further development.

scholarly journals Analysis of Stress-Strain States in the Vicinity of Mining Excavations in a Rock Mass with Variable Mechanical Properties

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5567
Author(s):  
Marek Jendryś ◽  
Stanisław Duży ◽  
Grzegorz Dyduch
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Numerical Simulations ◽  
Mechanical Parameters ◽  
Mining Operations ◽  
Axial Forces ◽  
Internal Forces ◽  
Random Variability ◽  
The Stability ◽  
The Impact

Rock mass is a medium created through processes that have lasted over four billion years, and its intrinsic feature is the variability of the parameters that describe it. A particularly high variability of mechanical parameters is observed in Carboniferous sedimentary and metamorphic rocks. The mechanical properties, especially the rock mass strength, are essential for the design and maintenance of the stability of excavations conducted in it and for the safe conduct of mining operations. This article presents the test results confirming the random variability of the mechanical parameters of the rock mass. The second part of the article presents the results of numerical simulations mapping the Carboniferous rock mass along with a 1000 m deep tunnel excavation protected by steel arch supports. Numerical simulations were carried out for models with different variability coefficients of strength and deformation parameters, and the obtained results were analyzed in terms of damage zones and rock mass stress state as well as axial forces in the modelled supports. The results of the simulation demonstrate the impact of the variability of rock mass properties on its state in the vicinity of the excavation and, consequently, on the internal forces in the steel supports and their uneven loading along the length of the excavation. This fact should be taken into account in their design.

scholarly journals Experimental Research into the Evolution of Permeability in a Broken Coal Mass under Cyclic Loading and Unloading Conditions

2019 ◽  
Vol 9 (4) ◽  
pp. 762 ◽  
Author(s):  
Bo Li ◽  
Quanle Zou ◽  
Yunpei Liang
Keyword(s):  
Cyclic Loading ◽  
Coal Sample ◽  
Stress Sensitivity ◽  
Coal Mass ◽  
Repeated Loading ◽  
Particle Deformation ◽  
Cyclic Loading And Unloading ◽  
Coal Particles ◽  
Loading And Unloading ◽  
Broken Coal Mass

The permeability characteristics of a broken coal mass under repeated loading and unloading conditions exert significance on spontaneous combustion of coal in goaf during the mining of coal seam groups. Considering this, by using the seepage test system for broken coal-rock mass, seepage tests under cyclic loading and unloading conditions, were carried out on broken coal masses. The test results show that the fitting curves between permeability and effective stress, strain and porosity are a logarithmic function, cubic function and power function, respectively. Besides, the permeability of a broken coal sample under cyclic loading and unloading conditions is determined by its porosity, which conforms to the cubic law. With increased cyclic loading and unloading times, the permeability loss, stress sensitivity and the crushing amount of the broken coal sample were gradually reduced, but the particle size gradation of the broken coal sample gradually became better. During one loading and unloading cycle, the stress sensitivity of the permeability of coal samples in the loading stage was far higher than that in the unloading stage. In the loading stage, the re-arrangement, breakage and compressive deformation of coal particles can lead to a reduction in porosity, consequently resulting in a decreased permeability. In the unloading stage, only the permeability reduction of coal samples due to particle deformation can be recovered.

scholarly journals GEOPHYSICS APPLIED TO THE MAPPING OF NATURAL CAVES HOSTED IN IRON ORE IN CARAJÁS (PA), BRAZIL

2019 ◽  
Vol 37 (3) ◽  
pp. 249
Author(s):  
Maria Filipa Perez da Gama ◽  
Marco Antonio Braga ◽  
Marcelo Roberto Barbosa ◽  
Rafael Guimarães de Paula ◽  
Daniele Freitas Gonçalves ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Rock Mass ◽  
Geophysical Methods ◽  
Mining Operations ◽  
Near Surface ◽  
Geophysical Surveys ◽  
Iron Mine ◽  
Northern Brazil ◽  
Ground Penetrating ◽  
The Impact

 ABSTRACT. The Brazilian environmental licensing for mining activities requires technical-scientific studies to demonstrate that natural caves will be protected from the impact of the mining operations. This study presents the results of near-surface geophysical methods applied to geostructural mapping of the rock mass in which the caves are hosted. The ferruginous karstic terrains are challenging to the geophysical interpretation due to the caves’ modest dimensions and the large variations in the host rock physical properties. Electrical Resistivity and GPR (Ground Penetrating Radar) geophysical surveys, were performed overlaying a natural cave located in the surroundings of the N4EN iron mine, in the Carajás Province, northern Brazil. The resistivity data were useful to discriminate different lithotypes as well as the presence of humidity in the rock mass, while the GPR data revealed a detailed degree of fracturing of the rock mass. The presence of humidity and the highly fractured zones may constitute zones of greater fragility of the cave walls and ceiling.Keywords: speleology, GPR, electrical resistivity, near-surface geophysics.RESUMO. O licenciamento ambiental brasileiro para atividades de mineração requer que estudos técnico-científicos demonstrem que as cavernas serão protegidas do impacto das operações de mineração. Este artigo apresenta os resultados de métodos geofísicos rasos aplicados ao mapeamento geoestrutural do maciço rochoso em que as cavernas estão hospedadas. Os terrenos cársticos ferruginosos são desafiadores para a interpretação geofísica, devido às modestas dimensões das cavernas e às grandes variações nas propriedades físicas da rocha hospedeira. Levantamentos geofísicos de Resistividade Elétrica e GPR (Radar de Penetração no Solo) foram realizados sobre a uma caverna localizada no entorno da mina de ferro N4EN, na Província de Carajás, região Norte do Brasil. Os dados de resistividade foram úteis para discriminar diferentes litotipos, bem como a presença de umidade na massa rochosa, enquanto os dados de GPR revelaram em grau detalhado o fraturamento da massa rochosa. A presença de umidade e as zonas altamente fraturadas podem constituir zonas de maior fragilidade das paredes e teto da caverna.Palavras-chave: espeleologia, GPR, resistividade elétrica, geofísica rasa.

scholarly journals Spatial non-linearity of methane release dynamics in underground boreholes for sustainable mining

2020 ◽  
Vol 245 ◽  
pp. 522-530
Author(s):  
Ada Dzhioeva ◽  
Vladimir Brigida
Keyword(s):  
Sustainable Development ◽  
Rock Mass ◽  
Coal Mining ◽  
Methane Concentration ◽  
Mining Operations ◽  
Gas Drainage ◽  
Methane Release ◽  
Non Linear ◽  
Production Face ◽  
The Impact

The paper is devoted to the problem of increasing energy efficiency of coalmine methane utilization to provide sustainable development of geotechnologies in the context of transition to a clean resource-saving energy production. Its relevance results from the fact that the anthropogenic effect of coalmine methane emissions on the global climate change processes is 21 times higher than the impact of carbon dioxide. Suites of gassy coal seams and surrounding rocks should be classified as technogenic coal-gas deposits, while gas extracted from them should be treated as an alternative energy source. Existing practices and methods of controlling coalmine methane need to be improved, as the current “mine – longwall” concept does not fully take into account spatial and temporal specifics of production face advancement. Therefore, related issues are relevant for many areas of expertise, and especially so for green coal mining. The goal of this paper is to identify patterns that describe non-linear nature of methane release dynamics in the underground boreholes to provide sustainable development of geotechnologies due to quality improvement of the withdrawn methane-air mixture. For the first time in spatial-temporal studies (in the plane of CH4-S) of methane concentration dynamics, according to the designed approach, the parameter of distance from the longwall (L) is introduced, which allows to create function space for the analyzed process (CH4 of S-L). Results of coalmine measurements are interpreted using the method of local polynomial regression (LOESS). The study is based on using non-linear variations of methane concentration in the underground boreholes and specific features of their implementation to perform vacuum pumping in the most productive areas of the undermined rock mass in order to maintain safe aerogas conditions of the extraction block during intensive mining of deep-lying gassy seams. Identification of patterns in the influence of situational geomechanical conditions of coal mining on the initiation of metastable gas-coal solution transformation and genesis of wave processes in the coal-rock mass allows to improve reliability of predicting methane release dynamics, as well as workflow manageability of mining operations. Presented results demonstrate that development of high-methane Donbass seams is associated with insufficient reliability of gas drainage system operation at distances over 40 m behind the longwall face. Obtained results confirm a working hypothesis about the presence of spatial migration of methane concentration waves in the underground gas drainage boreholes. It is necessary to continue research in the area of estimating deviation angles of “advance fracturing” zone boundaries from the face line direction. Practical significance of research results lies in the possibility to use them in the development of scientific foundation for 3D gas drainage of a man-made coal-methane reservoir, taking into account spatial and temporal advancement of the production face.  

scholarly journals Cumulative Effects of Particulate Matter Pollution and Meteorological Variables on the Risk of Influenza-Like Illness

Viruses ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 556
Author(s):  
Kacper Toczylowski ◽  
Magdalena Wietlicka-Piszcz ◽  
Magdalena Grabowska ◽  
Artur Sulik
Keyword(s):  
Particulate Matter ◽  
Respiratory Infections ◽  
Nonlinear Models ◽  
Absolute Humidity ◽  
Influenza Viruses ◽  
Meteorological Variables ◽  
Exponential Relationship ◽  
Influenza Like Illness ◽  
Air Temperatures ◽  
The Impact

The cold season is usually accompanied by an increased incidence of respiratory infections and increased air pollution from combustion sources. As we are facing growing numbers of COVID-19 cases caused by the novel SARS-CoV-2 coronavirus, an understanding of the impact of air pollutants and meteorological variables on the incidence of respiratory infections is crucial. The incidence of influenza-like illness (ILI) can be used as a close proxy for the circulation of influenza viruses. Recently, SARS-CoV-2 has also been detected in patients with ILI. Using distributed lag nonlinear models, we analyzed the association between ILI, meteorological variables and particulate matter concentration in Bialystok, Poland, from 2013–2019. We found an exponential relationship between cumulative PM2.5 pollution and the incidence of ILI, which remained significant after adjusting for air temperatures and a long-term trend. Pollution had the greatest effect during the same week, but the risk of ILI was increased for the four following weeks. The risk of ILI was also increased by low air temperatures, low absolute humidity, and high wind speed. Altogether, our results show that all measures implemented to decrease PM2.5 concentrations would be beneficial to reduce the transmission of SARS-CoV-2 and other respiratory infections.

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