Mechanical Behavior and Permeability Evolution of Reconstituted Coal Samples under Various Unloading Confining Pressures—Implications for Wellbore Stability Analysis

Zhang, Qiangui; Fan, Xiangyu; Liang, Yun; Li, Minghui; Li, Guangzhi; Ma, Tianshou; Nie, Wen

doi:10.3390/en10030292

Cited by 29 publications

(10 citation statements)

References 34 publications

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“…e coal mining process is the unloading process of coal and rock, and the stress field is transformed into the unloading field consisted of the initial stress and unloading stress; Cao et al [14] studied unloading vibration induced by a high initial stress release during underground excavations by investigating the mechanical behavior and permeability of coal rock under different degrees of unloading confining pressure and reloading axial stress by a triaxial experimental apparatus. In [15], it was revealed that peak deviatoric stress of coal rock is lower than that in a conventional triaxial compression test, and the peak deviatoric stress linearly relates the degree of unloading confining pressure. Huang et al [16] developed an idea that it is inappropriate to use the mechanical parameters obtained under loading conditions to calculate and analyze the deformation and slope stability during the excavation and unloading process.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Chang

Cai

Zhou

et al. 2019

Advances in Civil Engineering

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In the process of open-pit excavation and stacking of dump along the side wall, the rock mass inside the composite slope undergoes complicated loading and unloading effect, which are manifested as triaxial stress → horizontal unloading → axial loading. In this study, a corresponding mechanical model of crack propagation in composite slope under loading and unloading effects was established. The stress-strain curves and deformation characteristics of rock under different stress paths were studied. A series of different tests under unloading pressure condition were carried out to study the behavior of the rock fracture under different confining pressure paths. The results showed that under the same initial stress conditions, the deviator stress required for rock unloading failure was less than that of the conventional triaxial compression. The axial deformation of rock samples was gradually increased with the increase of unloading, and the unloading easily led to rock failure. By analyzing the crack propagation mechanism under loading and unloading stress field, the analytic relation of the limit height of the composite slope with the crack morphology as the variation was determined when crack propagation occurred near the slope surface. This study provides a technical note on local damage and cracks propagation of a fractured rock mass under the loading-unloading effects in high composite slope.

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Section: Introductionmentioning

confidence: 99%

Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Chang

Cai

Zhou

et al. 2019

Advances in Civil Engineering

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“…e mining stress and original rock stress superimpose on the coal seam and roof rock, which is similar to a cyclic loading condition. Coal mine disasters are mostly generated by the overall structure of coal seam and roof [59][60][61][62][63][64][65][66][67][68][69][70]. Many coal mine disasters demonstrate that roof-and-floor rock has a loading effect on the failure of the coal seam.…”

Section: Discussionmentioning

confidence: 99%

Study on Failure Modes and Energy Evolution of Coal-Rock Combination under Cyclic Loading

Song

Liu

Tan

et al. 2020

Shock and Vibration

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The loading modes and roof lithology have a significant influence on the mechanical properties of coal seams. To reveal the failure modes and energy evolution law of underground coal during the mining process, conventional uniaxial and uniaxial cyclic loading tests were carried out on three types of samples: coal, rock, and coal-rock combinations. The results show that the samples mainly behave with three failure modes (shear slip, tensile splitting, and fracture), and all the coal sections in the coal-rock combinations fail, whereas most rock sections remain intact. The compressive strength of the coal-rock combination is higher than coal and much smaller than rock. Compared with the conventional uniaxial loading condition, both the maximum deformation before failure and Young’s modulus under the cyclic loading condition are greater, and the latter increases quadratically with the cycle index. The energy densities are also calculated, and their variations are analysed in detail. The results show that with increasing cycle index, both the elastic energy stored in the sample and the dissipated energy increase in a quadratic function, and the failure process becomes more intense. This research reveals the failure modes, deformation characteristics, and energy evolution of the coal-rock combination under different loading conditions, which can provide strong support for controlling underground surrounding rocks of the coal face and roadway in coalmines.

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“…Zhang et al 26 used the unsteady-state method determined that the gas water relative permeability. Zhang et al 27 investigated the mechanical behavior and permeability of coal rock under different degrees of unloading confining pressure-reloading axial stress. For the effect of temperature on the permeability of coal and rock, Li et al 28 studied the relationship between permeability and temperature and stress using adsorbed gas methane and nonadsorbed gas helium.…”

Section: Introductionmentioning

confidence: 99%

Test and analysis of mechanics and permeation properties of raw coal

Yang

Zhang

et al. 2019

Energy Science & Engineering

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In this paper, we investigated the mechanics and permeation properties of the raw coal sample during loading and unloading process, and come to some conclusions: the permeability of the sample increases nonlinearly during the unloading confining pressure process. The larger the gas pressure is, the greater the increase range of the permeability will be. The larger the confining pressure unloading amplitude is, the greater the increase range of the permeability will be. In the loading process, the permeability and the axial strain of the specimen change in a “V” shape. As the gas pressure increases, the peak strength of the specimen gradually decreases, and fitted the gas pressure and the peak strength are accordance with the linear relationship. As the confining pressure increase, the peak strength of the sample gradually increases, and fitted the confining pressure and the peak strength are accordance with the exponential function. The internal friction angle of the coal sample was 43.22°, and the cohesion was 3.77 MPa. The relationship between the fitted gas pressure and internal friction angle, gas pressure and cohesion is in line with linear functions. Maintain an axial stress constant, unloaded confining pressure to a constant state of target value, the permeability of specimen shows a constant pressure boosting flow zone, the relationship between permeability and deviatoric stress is accordance with the ExpDec1 function during the process of unloading confining pressure and prepeak loading axial stress.

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Mechanical Behavior and Permeability Evolution of Reconstituted Coal Samples under Various Unloading Confining Pressures—Implications for Wellbore Stability Analysis

Cited by 29 publications

References 34 publications

Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Effects of the Loading and Unloading Conditions on Crack Propagation in High Composite Slope of Deep Open‐Pit Mine

Study on Failure Modes and Energy Evolution of Coal-Rock Combination under Cyclic Loading

Test and analysis of mechanics and permeation properties of raw coal

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