Article
Engineering, Geological
Beichen Yu, Dongming Zhang, Shujian Li, Bin Xu, Chao Liu, Yubing Liu
Summary: Studying the anisotropic seepage characteristics of coal is important for the safe and efficient extraction of coalbed methane. This study experimentally investigated the effect of induced damage on the Biot's coefficient alpha and permeability of coal under different stress states. The results show that alpha and permeability are closely related to fracture evolution and exhibit significant anisotropy. A new coal permeability model considering the damage effect and anisotropy of Biot's coefficient is proposed.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Geosciences, Multidisciplinary
Jun Tang, Jie Zhu, Tangsha Shao, Jinge Wang, Yaodong Jiang
Summary: Fracture compressibility and strain conditions play a crucial role in coal permeability evolution. The new permeability model derived in this study, considering variable fracture compressibility, showed more accurate results compared to the model with constant fracture compressibility. Coal fracture compressibility generally decreases with increasing effective stress and responds differently to changes in gas pressure and type.
NATURAL RESOURCES RESEARCH
(2021)
Article
Engineering, Chemical
Yubing Liu, Dong Zhao, Yiteng Li, Li Zhang
Summary: This study investigated the permeability of intact and fractured coal specimens and analyzed the fitting results based on established permeability models. The results showed that fractured coal exhibited an L-shaped permeability trend, while intact coal had an S-shaped trend. Macroscopic fractures increased the permeability of coal samples by 1-3 orders of magnitude, and the slip of the fracture surface resulted in permeability fluctuations.
Article
Geosciences, Multidisciplinary
Jianbao Liu, Zhimin Song, Chengtao Yang, Bing Li, Jiangang Ren, Ming Xiao
Summary: The study shows that the axial pressure has a significant influence on the permeability of the coal seam. As the axial pressure increases, the permeability of the coal seam initially decreases slightly and then gradually increases. When the axial pressure exceeds 30 MPa, the permeability of the coal seam sharply increases. The increase in axial pressure can also improve the gas drainage efficiency of the coal seam.
FRONTIERS IN EARTH SCIENCE
(2022)
Article
Mining & Mineral Processing
Bing Chen, Baotang Shen, Shichuan Zhang, Yangyang Li, Haiyang Jiang
Summary: This study investigates the law and mechanism of the influence of confining pressure constraints on the three-dimensional morphology of natural fractures. The experimental results show that the micro-failure mechanisms and three-dimensional morphology features of tension fracture surfaces and shear fracture surfaces are affected by different confining pressure constraints. The findings are significant for selecting technical parameters for enhanced geothermal development and ensuring the safety of underground mine engineering.
INTERNATIONAL JOURNAL OF MINING SCIENCE AND TECHNOLOGY
(2022)
Article
Energy & Fuels
Beichen Yu, Chao Liu, Weixing Chen, Jun Lu, Yubing Liu
Summary: This study conducted hydraulic fracturing tests of coal under different test schemes and found that pulse pressurization can decrease the breakdown pressure of coal by promoting inter-granular fractures. However, the stepwise pressurization scheme may lead to abnormally high breakdown pressure due to the obstruction of fracture propagation. A breakdown pressure prediction model based on the tensile stress criterion was established to effectively predict the breakdown pressure in different test schemes.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2022)
Article
Geosciences, Multidisciplinary
Yubing Liu, Enyuan Wang, Changbao Jiang, Dongming Zhang, Minghui Li, Beichen Yu, Dong Zhao
Summary: During deep underground coal mining, the mechanical and permeability characteristics of initially fractured coal were investigated under true triaxial stresses. The results show that initially fractured coal exhibits semi-brittle Class I failure modes and forms new failure planes different from intact coal samples. The peak strength of initially fractured coal is observed when the maximum principal stress is perpendicular to bedding planes, while minimum values occur when the maximum principal stress is parallel to butt cleats. The permeability of initially fractured coal decreases due to the presence of pulverized coal grains.
NATURAL RESOURCES RESEARCH
(2023)
Article
Engineering, Geological
Chongyang Wang, Dongming Zhang, Beichen Yu, Shujian Li
Summary: The true triaxial loading-unloading tests of coal samples were conducted to analyze the deformation, seepage, damage, strength, and failure characteristics. The impact of gas pressure on permeability and yield conditions were investigated, and numerical simulation software was used to verify the true triaxial loading-unloading process. The results showed that the volumetric strain of the samples underwent a process of compaction, flatness, and re-compaction with time. The permeability was negatively correlated with volumetric strain. The damage factor and initial damage point of the samples increased with gas pressure, and the sample experienced different behaviors at different pressures.
ROCK MECHANICS AND ROCK ENGINEERING
(2023)
Article
Geosciences, Multidisciplinary
Rongxi Shen, Zhoujie Gu, Zhentang Liu, Enlai Zhao, Zesheng Zang, Xin Zhou, Xiaoliang Li, Wei Liu, Xi Wang
Summary: A full understanding of the dynamic mechanical characteristics of coal samples under true triaxial conditions is crucial for preventing and controlling dynamic disasters in deep coal and rock. The study found that the transmission amplitude decreases as sigma 1 increases and increases with the impact velocity. The peak stress and absorbed energy of coal decrease with the increase in sigma 1 under true triaxial conditions. Under uniaxial and true triaxial conditions, the peak stress and absorbed energy of coal increase with the increase in impact velocity, and the stress change under true triaxial conditions is more sensitive to the dynamic load. Compared to uniaxial impact, the damage degree of coal samples under true triaxial conditions is lower. The fractal dimension of broken blocks increases linearly with the increase in sigma 1 and dynamic load, indicating an intensified degree of broken coal. This study effectively reveals the failure mechanism of coal under unequal static load and dynamic load.
NATURAL RESOURCES RESEARCH
(2023)
Article
Engineering, Environmental
Minke Duan, Changbao Jiang, Xianwei Guo, Ke Yang, Jinzhou Tang, Zhiqiang Yin, Xuelong Hu
Summary: The bedding angle and stress state have a significant influence on the seepage and mechanical properties of coal. Increasing the bedding angle leads to a decrease in peak stress, an increase in permeability and residual strength, and an increase in sensitivity of permeability to stress. Additionally, increasing the bedding angle results in an increase in dissipation energy and a change in the failure mode of coal.
BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT
(2022)
Article
Energy & Fuels
Jianhua Li, Heping Xie, Jun Lu, Mingzhong Gao, Bobo Li, Yan Wu
Summary: This study proposes a permeability model for anisotropic coal by combining gas sorption effects and three-dimensional stress compression, and quantitatively analyzes the effect of stress-induced fracture expansion on the fracture-matrix system. Seepage tests and measurements of coal, sandstone, and composite coal-rock were conducted, and the results show that stress first causes fracture compression, but with the continuous increase of stress, fracture initiation and expansion increase the seepage channel of rock and lead to a sudden increase in permeability.
GEOMECHANICS AND GEOPHYSICS FOR GEO-ENERGY AND GEO-RESOURCES
(2022)
Article
Engineering, Geological
Beichen Yu, Dongming Zhang, Bin Xu, Minghui Li, Chao Liu, Weijing Xiao
Summary: This study investigates the influence of induced damage on the effective stress coefficient and permeability of sandstone under true triaxial stress conditions. The results show that damage evolution and fracture propagation are closely related to the effective stress coefficient and permeability. Loading deviatoric stress can cause damage, leading to non-linear stress-strain relationships and volume expansion of the rock, which in turn increases permeability.
INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES
(2022)
Article
Energy & Fuels
Tongwen Jiang, Wei Yao, Xiongwei Sun, Chunyan Qi, Xing Li, Kaiwen Xia, Jie Zhang, M. H. B. Nasseri
Summary: The experimental investigation on the anisotropic permeability behavior of fractured sandstones in three principal stress directions shows that directional permeability of fractured specimens is about one order of magnitude higher than intact rock at the same stress state, and the permeability variation is significantly related to fracture geometry.
JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING
(2021)
Article
Energy & Fuels
Yong-liang Xu, Ze-jian Liu, Lan-yun Wang, Zhi-guang Lv, Jin-dong Wu, Min-jie Li
Summary: This study reveals various aspects of coal spontaneous combustion through experiments and theoretical analysis, such as thermal properties, the impact of particle size on combustion, and the effects of stress. The findings provide insights into coal fire prevention and control.
Article
Energy & Fuels
Kangwu Feng, Beichen Yu, Dongming Zhang
Summary: This study conducted a large-scale three-dimensional physical simulation experimental study of hydraulic fracturing with high temperature of oil sand reservoir under true triaxial stress state. The results showed that the hydraulic breakdown pressure of oil sands increases with the increase in sigma(2) and a new oil sand breakdown pressure prediction model was developed. Shear fractures formed under low sigma(2) conditions showed a better permeability enhancement effect than tensile fractures formed under high sigma(2) conditions.
ENERGY SCIENCE & ENGINEERING
(2022)
