Experimental Study on the Permeability Evolution and Gas Flow Law of Post-Strength Soft Coal

Hou, Chao; Ma, Jianbiao; Jin, Xiaoguang; Ni, Du

doi:10.3390/app10031039

Cited by 3 publications

(3 citation statements)

References 20 publications

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“…As a result, the mechanical properties and permeability characteristics of rocks are affected (Yao et al 2015;Chen et al 2018;Zhao et al 2016). To ensure the safety and stability of deep rock engineering, it is crucial to investigate the mechanical properties and permeability law of rocks under hydromechanical coupling conditions (Zhu et al 2015;Hou et al 2020;Zhou et al 2021;Kou et al 2021). However, there is a dearth of studies on the permeability characteristics of rocks under different degrees of damage and seepage pressure gradient throughout the entire stress-strain process.…”

Section: Introductionmentioning

confidence: 99%

Permeability Evolution and Damage Characterization of Sandstone under Various Confining Pressures and Seepage Pressure Gradients

Lin,

Long,

Wang

et al. 2023

Preprint

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In the realm of deep hydraulic engineering, diversion caverns often confront significant challenges due to high in-situ stress and high seepage pressure gradient. These conditions result in intricate mechanical behavior and permeability characteristics within the surrounding rock. In light of this, the present study aims to investigate the relationship between damage evolution and permeability characteristics of sandstone prior to failure under hydromechanical coupling conditions through a series of hydromechanical coupling tests. The results of these tests demonstrate that the strength and deformation resistance of sandstone exhibit variations corresponding to changes in the seepage pressure gradient. Moreover, an increase in seepage pressure gradient leads to a shift in the failure patterns of sandstone from low-inclination shear failure to steep-angle shear failure. Throughout the failure process of sandstone, the permeability curve initially decreases, followed by a rapid increase before ultimately stabilizing. Notably, the peak value of the permeability curve lags behind that of the stress-strain curve. Furthermore, when the seepage pressure gradient initially rises and then drops, the permeability of sandstone undergoes an irreversible change in the opposite direction, failing to return to its initial value. Based on these observations, a statistical damage model is proposed for rocks, accounting for hydromechanical coupling. Remarkably, the theoretical values derived from this model align well with experimental results. This model, grounded in the laws governing permeability evolution and damage properties of sandstone prior to failure, offers valuable guidance for monitoring and controlling rock stability in diversion caverns subjected to hydromechanical coupling actions.

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Section: Introductionmentioning

confidence: 99%

Permeability Evolution and Damage Characterization of Sandstone under Various Confining Pressures and Seepage Pressure Gradients

Lin,

Long,

Wang

et al. 2023

Preprint

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show abstract

“…In addition, the study also believes that the size and distribution of the stress field will directly affect the state of micro-cracks inside the rock, change the permeability inside the rock mass, and then affect the effective stress distribution inside the rock mass. The permeability of rock changes significantly after the rock reaches the yield stress [15][16][17][18][19][20][21]. The stress field and seepage field of the rock will affect each other.…”

Section: Introductionmentioning

confidence: 99%

Study on Hydro-Mechanical Coupling Failure and Permeability Enhancement Mechanisms for Sandstone with T-Shaped Fractures

Zhang

Pan

et al. 2023

Materials

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The rise in the connectivity of the fractures is a key task in oil/gas and geothermal exploitation systems. Natural fractures widely exist in underground reservoir sandstone, while the mechanical behavior of rock with fractures subjected to hydro-mechanical coupling loads is far from clear. This paper employed comprehensive experiments and numerical simulations to investigate the failure mechanism and permeability law for sandstone specimens with T-shaped faces subjected to hydro-mechanical coupling loads. The effects of crack closure stress, crack initiation stress, strength, and axial strain stiffness of the specimens under different fracture inclination angles are discussed, and the evolution processes of permeability are obtained. The results show that secondary fractures are created around the pre-existing T-shaped fractures through tensile, shear, or mixed modes. The fracture network causes an increase in the permeability of the specimen. T-shaped fractures have a more significant effect on the strength of the specimens than water. The peak strengths of T-shaped specimens decreased by 34.89%, 33.79%, 46.09%, 39.32%, 47.23%, 42.76%, and 36.02%, respectively, compared with intact specimen without water pressure. With the increase in deviatoric stress, the permeability of T-shaped sandstone specimens decreases first, then increases, reaching its maximum value when macroscopic fractures are formed, after which the stress suddenly decreases. When the prefabricated T-shaped fracture angle is 75°, the corresponding permeability of the sample at failure is maximum, with a value of 15.84 × 10−16 m2. The failure process of the rock is reproduced through numerical simulations, in which the influence of damage and macroscopic fractures on permeability is discussed.

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“…Currently, coal and gas outburst mines still occupy a large proportion of China's production and under construction mines. From 2013 to 2017, the coal mine accidents in China caused by gas accounted for 11.21% of the total accidents [7].…”

Section: Introductionmentioning

confidence: 99%

Numerical and Similarity Simulation Study on the Protection Effect of Composite Protective Layer Mining with Gently Inclined Thick Coal Seam

Hou

Jiang-tao

2021

Shock and Vibration

Self Cite

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Protective layer mining, as a dominating method for preventing coal and gas outburst, is generally adopted in highly gassy coal mines. In the absence of a suitable thickness coal seam to serve as the protective layer, the rock-coal composite protective layer was proposed in this paper. We conducted a series of simulations and engineering measurements to investigate the protective effect under the mining of the rock-coal composite protective layer of the Zhongtai coal mine located in the Hebi area of Henan, China. The numerical simulation analysis showed that, after the completion of protective layer mining, the minimum vertical stress of the No. 2-1 coal seam had been reduced to 3.46 MPa. The maximum vertical displacement of the No. 2-1 coal seam is 455.01 mm. The maximum expansion deformation of the No. 2-1 coal seam is 9.77‰; the effective pressure relief range is as long as 160 m. The similarity simulation experiment revealed that, after the completion of protective layer mining, the minimum vertical stress of the No. 2-1 coal seam is 4.0 MPa. The maximum vertical displacement of the No. 2-1 coal seam is 640 mm. The maximum expansion deformation of the No. 2-1 coal seam is 26.37‰; the effective protection range reaches 130 m. The engineering measurements demonstrated that the variation law of gas drainage parameters in the protected layer corresponds to the protected layer's vertical stress distribution law in numerical simulation and similarity simulation. With the exploitation of the composite protective layer, the protective layer’s pressure begins to release. The average gas drainage concentration is 2-3 times of that before the composite protective layer mining.

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Experimental Study on the Permeability Evolution and Gas Flow Law of Post-Strength Soft Coal

Cited by 3 publications

References 20 publications

Permeability Evolution and Damage Characterization of Sandstone under Various Confining Pressures and Seepage Pressure Gradients

Permeability Evolution and Damage Characterization of Sandstone under Various Confining Pressures and Seepage Pressure Gradients

Study on Hydro-Mechanical Coupling Failure and Permeability Enhancement Mechanisms for Sandstone with T-Shaped Fractures

Numerical and Similarity Simulation Study on the Protection Effect of Composite Protective Layer Mining with Gently Inclined Thick Coal Seam

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