scholarly journals COAL PERMEABILITY CHANGE CAUSED BY MINING-INDUCED STRESS

Mining Scince ◽  
2019 ◽  
Vol 26 ◽  
Author(s):  
Lulu Zhang ◽  
Bo Li ◽  
Jianping Wei ◽  
Zhihui Wen ◽  
Yongjie Ren
Keyword(s):  
Experimental Data ◽  
Effective Stress ◽  
Axial Stress ◽  
Sensitivity Index ◽  
Permeability Change ◽  
Permeability Evolution ◽  
Confining Stress ◽  
Coal Permeability ◽  
Calculation Results ◽  
Loading And Unloading

To study coal permeability evolution under the influence of mining actions, we conducted a sensitivity index test on permeability to determine the influence of axial and confining stresses on coal permeability. Loading and unloading tests were performed afterward, and the differences between loading and unloading paths in terms of strain and permeability were studied. A permeability evolution model was built in consideration of absorption swelling and effective stress during modeling. An effective stress calculation model was also built using axial and confining stresses. The calculation results of the two models were compared with experimental data. Results showed that permeability were more sensitive to confining stress than axial stress, and effective stress placed a large weight on confining stress. Large axial and radial deformations at peak strength were observed during unloading. In the unloading phase, the permeability of coal began to increase, and the increment was enhanced by large initial axial stress when confining stress was loaded. permeability sensitivity to axial and confining stresses were used to explain these permeability changes. The calculation results of the models fitted the experimental data well. Therefore, the proposed models can be used to calculate effective stress on the basis of axial and confining stresses and describe permeability change in coal under the influence of mining actions.

scholarly journals Coupled Effects of Stress, Moisture Content and Gas Pressure on the Permeability Evolution of Coal Samples: A Case Study of the Coking Coal Resourced from Tunlan Coalmine

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1653
Author(s):  
Guofu Li ◽  
Yi Wang ◽  
Junhui Wang ◽  
Hongwei Zhang ◽  
Wenbin Shen ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coalbed Methane ◽  
Gas Permeability ◽  
Axial Stress ◽  
Gas Pressure ◽  
Pressure Curve ◽  
Permeability Evolution ◽  
Confining Stress ◽  
Qinshui Basin ◽  
Gas Seepage

Deep coalbed methane (CBM) is widely distributed in China and is mainly commercially exploited in the Qinshui basin. The in situ stress and moisture content are key factors affecting the permeability of CH4-containing coal samples. Therefore, considering the coupled effects of compressing and infiltrating on the gas permeability of coal could be more accurate to reveal the CH4 gas seepage characteristics in CBM reservoirs. In this study, coal samples sourced from Tunlan coalmine were employed to conduct the triaxial loading and gas seepage tests. Several findings were concluded: (1) In this triaxial test, the effect of confining stress on the permeability of gas-containing coal samples is greater than that of axial stress. (2) The permeability versus gas pressure curve of coal presents a ‘V’ shape evolution trend, in which the minimum gas permeability was obtained at a gas pressure of 1.1MPa. (3) The gas permeability of coal samples decreased exponentially with increasing moisture content. Specifically, as the moisture content increasing from 0.18% to 3.15%, the gas permeability decreased by about 70%. These results are expected to provide a foundation for the efficient exploitation of CBM in Qinshui basin.

scholarly journals Evolution of Coal Permeability during Gas Injection—From Initial to Ultimate Equilibrium

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2800 ◽  
Author(s):  
Xingxing Liu ◽  
Jinchang Sheng ◽  
Jishan Liu ◽  
Yunjin Hu
Keyword(s):  
Effective Stress ◽  
Local Equilibrium ◽  
Fracture Aperture ◽  
Permeability Evolution ◽  
Full Spectrum ◽  
Coal Permeability ◽  
Fracture Pressure ◽  
Permeability Changes ◽  
Apparent Equilibrium ◽  
Non Equilibrium

The evolution of coal permeability is vitally important for the effective extraction of coal seam gas. A broad variety of permeability models have been developed under the assumption of local equilibrium, i.e., that the fracture pressure is in equilibrium with the matrix pressure. These models have so far failed to explain observations of coal permeability evolution that are available. This study explores the evolution of coal permeability as a non-equilibrium process. A displacement-based model is developed to define the evolution of permeability as a function of fracture aperture. Permeability evolution is tracked for the full spectrum of response from an initial apparent-equilibrium to an ultimate and final equilibrium. This approach is applied to explain why coal permeability changes even under a constant global effective stress, as reported in the literature. Model results clearly demonstrate that coal permeability changes even if conditions of constant effective stress are maintained for the fracture system during the non-equilibrium period, and that the duration of the transient period, from initial apparent-equilibrium to final equilibrium is primarily determined by both the fracture pressure and gas transport in the coal matrix. Based on these findings, it is concluded that the current assumption of local equilibrium in measurements of coal permeability may not be valid.

scholarly journals Permeability Prediction in Deep Coal Seam: A Case Study on the No. 3 Coal Seam of the Southern Qinshui Basin in China

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Pinkun Guo ◽  
Yuanping Cheng
Keyword(s):  
Coal Seam ◽  
Effective Stress ◽  
Axial Stress ◽  
Gas Pressure ◽  
Coal Bed ◽  
Stress And Strain ◽  
Qinshui Basin ◽  
Coal Permeability ◽  
Permeability Prediction ◽  
Southern Qinshui Basin

The coal permeability is an important parameter in mine methane control and coal bed methane (CBM) exploitation, which determines the practicability of methane extraction. Permeability prediction in deep coal seam plays a significant role in evaluating the practicability of CBM exploitation. The coal permeability depends on the coal fractures controlled by strata stress, gas pressure, and strata temperature which change with depth. The effect of the strata stress, gas pressure, and strata temperature on the coal (the coal matrix and fracture) under triaxial stress and strain conditions was studied. Then we got the change of coal porosity with strata stress, gas pressure, and strata temperature and established a coal permeability model under tri-axial stress and strain conditions. The permeability of the No. 3 coal seam of the Southern Qinshui Basin in China was predicted, which is consistent with that tested in the field. The effect of the sorption swelling on porosity (permeability) firstly increases rapidly and then slowly with the increase of depth. However, the effect of thermal expansion and effective stress compression on porosity (permeability) increases linearly with the increase of depth. The most effective way to improve the permeability in exploiting CBM or extracting methane is to reduce the effective stress.

Simulating Coal Permeability Change as a Function of Effective Stress Using a Microscale Digital Rock Model

2021 ◽  
Author(s):  
Huaimin Dong ◽  
Yihuai Zhang ◽  
Maxim Lebedev ◽  
Muhammad Arif ◽  
Yujie Yuan ◽  
...  
Keyword(s):  
Effective Stress ◽  
Permeability Change ◽  
Coal Permeability ◽  
Digital Rock ◽  
Rock Model

Permeability and Effective Stress in Dipping Gas Shale Formation With Bedding—Experimental Study

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Yufei Chen ◽  
Changbao Jiang ◽  
Guangzhi Yin ◽  
Andrew K. Wojtanowicz ◽  
Dongming Zhang
Keyword(s):  
Normal Stress ◽  
Effective Stress ◽  
Bedding Plane ◽  
Permeability Change ◽  
Permeability Evolution ◽  
Tangential Stresses ◽  
Significance Levels ◽  
Percent Contribution ◽  
Shale Formation ◽  
Shale Permeability

Abstract Shale gas well deliverability and economics depend on extremely low permeability that is not only dependent on the rock bedding trend but also controlled by in situ stresses. The purpose of this study was to determine relative contributions of normal and tangential stresses with respect to the rock bedding plane on permeability evolution of shale. The study involved an analysis of the rock bedding structure, followed by triaxial testing of rock samples and theoretical modeling. Also simulated were the effects of stress-bedding and load cycling. The results showed shale permeability reduction during the stress loading process and its gradual recovery during the unloading process. Permeability change was more pronounced in response to normal stress but some effects of the tangential stresses were also observed. Moreover, a theoretical model was derived to describe permeability change with effective stress in the presence of normal and tangential stresses. The model was empirically matched with the experimental results. The assessment of relative contributions of normal and tangential stresses was quantified with the analysis of variance (ANOVA). The analysis revealed significance levels of normal stress, and two tangential stresses σt1 and σt2 on shale permeability as 81%, 5%, and 14%, respectively. An almost 20-percent contribution of tangential stress loading to permeability response indicates a need for the improvement in computing effective stress. Therefore, a new method was suggested to determine effective stress when predicting permeability evolution of shale.

Refined thermal calculation of the locomotive heat engine collector

2020 ◽  
pp. 56-58
Author(s):  
P.V. Gubarev ◽  
D.V. Glazunov ◽  
V.G. Ruban ◽  
A.S. Shapshal
Keyword(s):  
Experimental Data ◽  
Electric Motor ◽  
Heat Balance ◽  
Thermal Imaging ◽  
Heat Engine ◽  
Thermal Calculation ◽  
Calculation Results ◽  
Cooling Air ◽  
The Heat Balance ◽  
Traction Electric Motor

The thermal calculation of the locomotive traction engine collector is proposed. The equations of the heat balance of its elements are obtained taking into account the cooling air. The calculation results and experimental data of thermal imaging control are presented. Keywords: traction electric motor, collector, thermal calculation, thermal imaging control. [email protected]

Parametric study of multi-story, perforated, partially grouted masonry walls subjected to in-plane cyclic actions

2020 ◽  
Author(s):  
Klaus Medeiros ◽  
Kyle Chavez ◽  
Fernando S. Fonseca ◽  
Guilherme Parsekian ◽  
Nigel G. Shrive
Keyword(s):  
Experimental Data ◽  
Shear Strength ◽  
Aspect Ratio ◽  
Load Capacity ◽  
Axial Stress ◽  
Reinforcement Ratio ◽  
Masonry Walls ◽  
Finite Element Models ◽  
Initial Stiffness ◽  
Vertical Reinforcement

Finite element models were developed to assess the influence of several parameters on the load capacity, deflection, and initial stiffness of multi-story, partially grouted masonry walls with openings. The base model was validated with experimental data from three walls. The analyses indicated that the load capacity of masonry walls was considerably sensitive to the ungrouted and grouted masonry strengths and mortar shear strength; moderately sensitive to the vertical reinforcement ratio and aspect ratio; slightly sensitive to the axial stress; and almost insensitive to the opening size, reinforcement spacing, and horizontal reinforcement ratio. The deflection of the walls had well-defined correlations with the masonry strength, vertical reinforcement, axial stress and aspect ratio. The initial stiffness was especially sensitive to the axial stress and the aspect ratio, but weakly correlated with the opening size, and the spacing and size of the reinforcement.

Tests on Mechanical Properties and Anti-Penetration Performance of Steel-Fiber Reactive Powder Concrete

2013 ◽  
Vol 671-674 ◽  
pp. 1761-1765
Author(s):  
Yong Liu ◽  
Chun Ming Song ◽  
Song Lin Yue
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Steel Fiber ◽  
Reactive Powder Concrete ◽  
Calculation Results ◽  
Reactive Powder ◽  
Penetration Tests

In order to get mechanical properties ,some RPC samples with 5% steel fiber are tested, many groups data were obtained such as compressive strength, shear strength and fracture toughness. And a group of tests on RPC with 5% steel-fiber under penetration were also conducted to validate the performance to impact. The penetration tests are carried out by the semi-AP projectiles with the diameter of 57 mm and earth penetrators with the diameter of 80 mm, and velocities of the two kinds of projectiles are 300～600 m/s and 800～900 m/s, respectively. By contrast between the experimental data and the calculation results of C30 reinforced concrete by using experiential formula under penetration, it shows that the resistance of steel-fiber RPC to penetration is 3 times as that of general C30 reinforced concrete.

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