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Fractal Fract
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Applications of Fractal Analysis in Underground Engineering
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Applications of Fractal Analysis in Underground Engineering

A special issue of Fractal and Fractional (ISSN 2504-3110). This special issue belongs to the section "Engineering".

Deadline for manuscript submissions: 1 May 2025 | Viewed by 15685

Special Issue Editors

Prof. Dr. Shihao Tu

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Guest Editor
Key Laboratory of Deep Coal Resource Mining (Ministry of Education of China), School of Mines, China University of Mining and Technology, Xuzhou 221116, China
Interests: disaster prevention and control in coal mining; theories and methods in mineral exploitation; intelligent mining; mining planning and sustainability
Prof. Dr. Lei Zhang

E-Mail Website
Guest Editor
School of Mines, China University of Mining and Technology, Xuzhou 221116, China
Interests: theories and methods in coal mining; green mining; rock mechanics and rock engineering
Prof. Dr. Chen Wang

E-Mail Website
Guest Editor
School of Mining, Guizhou University, Guiyang 550025, China
Interests: thin coal seam mining; intelligent mining; green mining; mining system engineering; rock stratum control in karst mountainous area
Special Issues, Collections and Topics in MDPI journals
Dr. Cun Zhang

E-Mail Website
Guest Editor
School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
Interests: mine pressure and strata control; mine water resources utilization; coal and gas co-mining; abandoned mine reuse
Special Issues, Collections and Topics in MDPI journals
Dr. Defu Zhu

E-Mail Website
Guest Editor
Key Laboratory of In-Situ Property-Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China
Interests: strata control; numerical calculation; coordinated mining of associated resources in coal measures
Dr. Kaijun Miao

E-Mail Website
Guest Editor
School of Mines, China University of Mining and Technology, Xuzhou 221116, China
Interests: stope rock formation control; mining rock mass seepage mechanics; coal mining shallow water resources protection; water inrush disaster prevention and control

Special Issue Information

Dear Colleagues,

Fractal geometry is an important tool to describe complex natural phenomena. With the development of fractal mechanics, fractal has also been widely applied to the field of rock mechanics and engineering, especially in joints, mining-induced fractures, rock fragmentation, mining-induced rock mass seepage and heat conduction. For many randomly distributed rock parameters, fractal analysis has become an important quantitative characterization method. Due to the differences in fractal dimensions obtained by different fractal measurement methods, there is controversy about fractal characterization internationally. However, fractal as a new perspective can quantitatively describe the chaos and roughness has been recognized. Joints, fractures and voids not only affect the strength of rocks, but also are important channels for fluid migration. It is found that the fractal dimension is related to the rock response characteristics of engineering disturbance. The methods of obtaining channel distribution are mainly physical perspective of small samples, numerical simulation and similar simulation. The fractal dimension analysis of the later image processing process has become a research hotspot. In addition, in view of the complexity, concealment and danger of underground engineering, the fractal analysis of massive data provides a new direction for guiding high efficiency and safe production. Therefore, it is necessary to carry out a lot of research work to determine which fractal dimension measurement method is more conducive to understanding the mechanism of rock mechanics and guiding rock mechanics engineering. The scope of this Special Issue includes, but is not limited to, the following topics:

  • Fractal quantitative characterization of natural joints and fractures in rock.
  • Fractal characteristics and engineering application of rock fracture development and crushing process.
  • Fractal analysis of digital image processing of joints and fractures.
  • Fractal analysis of seepage characteristics of mining rock mass.
  • Fractal characteristics of water / gas / thermal diffusion law in fractured rock mass.
  • Fractal characteristics and evolution law of mining-induced overburden fractures and ground fissures.
  • Fractal analysis of monitoring signals and information of underground engineering disaster prevention and control.
  • Fractal characteristics and application of underground engineering big data.

Prof. Dr. Shihao Tu
Prof. Dr. Lei Zhang
Prof. Dr. Chen Wang
Dr. Cun Zhang
Dr. Defu Zhu
Dr. Kaijun Miao
Guest Editors

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Published Papers (13 papers)

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Research

15 pages, 2574 KiB  
Article
The Effect of Organic Acid Modification on the Pore Structure and Fractal Features of 1/3 Coking Coal
by Jiafeng Fan and Feng Cai
Fractal Fract. 2025, 9(5), 283; https://doi.org/10.3390/fractalfract9050283 - 26 Apr 2025
Viewed by 74
Abstract
The acidification modification of coal seams is a significant technical measure for transforming coalbed methane reservoirs and enhancing the permeability of coal seams, thereby improving the extractability of coalbed methane. However, the acids currently used in fracturing fluids are predominantly inorganic acids, which [...] Read more.
The acidification modification of coal seams is a significant technical measure for transforming coalbed methane reservoirs and enhancing the permeability of coal seams, thereby improving the extractability of coalbed methane. However, the acids currently used in fracturing fluids are predominantly inorganic acids, which are highly corrosive and can contaminate groundwater reservoirs. In contrast, organic acids are not only significantly less corrosive than inorganic acids but also readily bind with the coal matrix. Some organic acids even exhibit complexing and flocculating effects, thus avoiding groundwater contamination. This study focuses on the 1/3 coking coal from the Guqiao Coal Mine of Huainan Mining Group Co., Ltd., in China. It systematically investigates the fractal characteristics and chemical structure of coal samples before and after pore modification using four organic acids (acetic acid, glycolic acid, oxalic acid, and citric acid) and compares their effects with those of hydrochloric acid solutions at the same concentration. Following treatment with organic acids, the coal samples exhibit an increase in surface fractal dimension, a reduction in spatial fractal dimension, a decline in micropore volume proportion, and a rise in the proportions of transitional and mesopore volumes, and the structure of the hydroxyl group and oxygen-containing functional group decreased. This indicates that treating coal samples with organic acids enhances their pore structure and chemical structure. A comparative analysis reveals that hydrochloric acid is more effective than acetic acid in modifying coal pores, while oxalic acid and citric acid outperform hydrochloric acid, and citric acid shows the best results. The findings provide essential theoretical support for organic acidification modification technology in coalbed methane reservoirs and hydraulic fracturing techniques for coalbed methane extraction. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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16 pages, 73322 KiB  
Article
A Study on the Mechanical Properties of Unbolted and Bolted Composite Rock Masses Under the Influence of Different Grain Sizes
by Chao Yuan, Xuanqi Huang, Weijun Wan and Yueyang Xu
Fractal Fract. 2025, 9(4), 232; https://doi.org/10.3390/fractalfract9040232 - 7 Apr 2025
Viewed by 239
Abstract
In order to explore the influence of grain size on the mechanical properties of unbolted and bolted composite rock masses, uniaxial compression tests were carried out on unbolted and bolted composite rock masses of different grain sizes. The characteristics of the variation in [...] Read more.
In order to explore the influence of grain size on the mechanical properties of unbolted and bolted composite rock masses, uniaxial compression tests were carried out on unbolted and bolted composite rock masses of different grain sizes. The characteristics of the variation in the strength, elastic modulus, Poisson’s ratio and energy parameters of composite rock masses with grain size were analyzed. The evolution process of crack propagation in the composite rock masses was studied, and the influence mechanism of rock grain size on the mechanical properties of the anchorage bearing structure of the rock surrounding the roadway was revealed. The results show that with an increase in the grain size, the peak strength and elastic modulus of a composite rock mass decrease gradually, and the post-peak residual strength, Poisson’s ratio and total input strain energy increase gradually. The evolution of crack propagation is from tensile cracking to tensile to shear mixed to shear cracking. Prestressed anchor bolts can effectively improve the peak strength and post-peak residual strength of composite rock masses and have inhibitory effects on crack propagation in the anchorage zone, such as weakening, deflection and crack arrest. Compared with an unbolted composite rock mass, the bearing capacity of a bolted composite rock mass is stronger, and its elastic modulus is significantly improved. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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23 pages, 4741 KiB  
Article
Fractal Dimension Warning via Microseismic Time–Energy Data During Rock Mass Failure
by Congcong Zhao, Shigen Fu, Zhen Wang, Mingbo Chi and Yinghua Huang
Fractal Fract. 2025, 9(3), 174; https://doi.org/10.3390/fractalfract9030174 - 13 Mar 2025
Viewed by 416
Abstract
The early warning of disasters such as ground pressure in deep hard rock mines has long constrained the safe and efficient development of mining activities. Based on fractal theory and fractal dimension interpretation, this study constructs a microseismic monitoring system for mining areas, [...] Read more.
The early warning of disasters such as ground pressure in deep hard rock mines has long constrained the safe and efficient development of mining activities. Based on fractal theory and fractal dimension interpretation, this study constructs a microseismic monitoring system for mining areas, extracting key elements, particularly time and energy elements. Using the box-counting method of fractal theory, the study investigates the fractal dimensions of microseismic time–energy elements, data interpretation, and disaster source early warning. Through parameter analysis, events related to local potential failure are identified and extracted, and disaster characteristics are revealed based on microseismic activity. A time–energy fractal dimension-based analysis method is developed for preliminary fractal analysis and prediction of regional damage. A time–energy-centered early warning model is constructed, narrowing the prediction range to a scale of 10 m. Based on the fractal interpretation of time–energy data, the prediction and early warning of rock mass failure in mining areas are achieved, with the reliability of nested energy warnings ranging between 91.7% and 96.2%. A comprehensive evaluation criterion for fractal dimension values is established, enabling accurate delineation of warning zones and providing scientific decision-making support for mine safety promotion. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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18 pages, 4844 KiB  
Article
Mechanical Response of Mudstone Based on Acoustic Emission Fractal Features
by Xianyin Chang, Yunpei Liang and Qican Ran
Fractal Fract. 2025, 9(2), 83; https://doi.org/10.3390/fractalfract9020083 - 25 Jan 2025
Cited by 4 | Viewed by 519
Abstract
In this study, the effect of the stress amplitude on the mechanical behavior of mudstone was systematically investigated by cyclic loading and unloading experiments and acoustic emission (AE) monitoring. The results show that at low-stress amplitudes, mudstone specimens show better elastic recovery ability, [...] Read more.
In this study, the effect of the stress amplitude on the mechanical behavior of mudstone was systematically investigated by cyclic loading and unloading experiments and acoustic emission (AE) monitoring. The results show that at low-stress amplitudes, mudstone specimens show better elastic recovery ability, lower damage accumulation and higher structural stability. At high-stress amplitudes, the irreversible damage of the mudstone increases significantly, the internal fractures gradually expand and penetrate through, and the risk of instability increases significantly. This is manifested by the gradual increase in cumulative irreversible strain of mudstone at different stress amplitudes, up to 0.144%. In addition, different stress amplitudes have significant effects on energy evolution characteristics, with low-stress amplitudes mainly showing elastic deformation and a high percentage of recoverable energy, while high-stress amplitudes show a high percentage of dissipated energy. Under the condition of high-stress amplitude, such as the mudstone specimen #4, the percentage of tensile failure is 81.15%. Tensile failure dominates at all stress amplitudes, where the failure mechanism within mudstone is mainly characterized by the extension of tensile-type fractures. Through the multifractal analysis of AE signals, this study reveals the effect of the stress amplitude on the fracture extension mode and failure mechanism of mudstone. As the stress amplitude increases, Δα and Δf show an increasing trend. This indicates that the fracture extension process transforms from a relatively homogeneous and simple mode to a more inhomogeneous and complex mode. This transformation reflects the nonlinear and multiscale fracture characteristics of mudstone under high-stress conditions. The results of this study help to understand the mechanical behavior of mudstone under cyclic loading during coal mining and provide theoretical support for safe coal production. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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13 pages, 3650 KiB  
Article
Fractal Evolution Characteristics of Pore Structure in Coal-Acidified Stimulation
by Dan Zhou, Zhiqiang Lv, Yunxing Cao, Gaofeng Liu, Xinsheng Zhang, Bin Shi, Junsheng Zhang and Shimin Liu
Fractal Fract. 2025, 9(2), 62; https://doi.org/10.3390/fractalfract9020062 - 22 Jan 2025
Viewed by 683
Abstract
The pore structure and connectivity of coal are the primary factors influencing the permeability of coal reservoirs. However, clay and carbonate minerals are commonly found filling the pores and fractures within coal. To address the impact of these minerals on fracturing effectiveness, acidic [...] Read more.
The pore structure and connectivity of coal are the primary factors influencing the permeability of coal reservoirs. However, clay and carbonate minerals are commonly found filling the pores and fractures within coal. To address the impact of these minerals on fracturing effectiveness, acidic fracturing technology has been introduced. This technique has proven to be an effective measure for enhancing the extraction rate of low-permeability coal seams with high mineral content. In this study, coal samples were treated with a 3% HCl solution, and the changes in the pore structure of the coal before and after acidification were analyzed through low-temperature nitrogen adsorption and X-ray diffraction (XRD) testing. The results were as follows: After acidification, the specific surface area, total pore volume, pore volume in different stages, and average pore size of the coal samples all significantly increased. Specifically, the BET specific surface area grew by an average of 4.8 times and the total pore volume expanded by an average of 7.7 times, with the pore volumes in the pore size ranges of <10 nm and 10–60 nm increasing by an average of 10.1 times and 7.7 times. The smoothness of the pore surface and connectivity of the pore structure in the coal samples improved, as indicated by decreased fractal dimensions D1 (reflecting pore surface roughness) and D2 (representing pore size distribution uniformity). The acidification mechanism was mainly attributed to the dissolution of carbonate minerals in the coal, which led to the removal of obstructive minerals such as ankerite and calcite that had accumulated in the coal pores. This resulted in the formation of new micropores and microfractures, achieving pore volume enhancement and pore expansion. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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17 pages, 11075 KiB  
Article
Uniaxial Compressive Failure Characteristics and Fractal Analysis of Mud–Sand Composite Rock Samples Based on Acoustic Emission Tests
by Changzheng Zhao, Shenggen Cao, Shihui Lang, Shuyu Du and Chiyuan Che
Fractal Fract. 2024, 8(12), 713; https://doi.org/10.3390/fractalfract8120713 - 30 Nov 2024
Viewed by 795
Abstract
In order to study the influence of rock combination types on their mechanical properties and failure characteristics, uniaxial compression tests of single rock samples and combined rock samples were conducted. Acoustic emission (AE) signals during the test process were collected, and the differences [...] Read more.
In order to study the influence of rock combination types on their mechanical properties and failure characteristics, uniaxial compression tests of single rock samples and combined rock samples were conducted. Acoustic emission (AE) signals during the test process were collected, and the differences in AE signals of single rock samples and combined rock samples were studied based on the fractal theory. The results showed that the peak strength, elastic modulus, peak strain, and failure degree of the combined rock samples are all between those of the two single rock samples. The AE ringing count gradually increases with the loading process and suddenly increases to the maximum when the rock sample fails. During this process, the phase trajectory volume corresponding to the ringing count shows an evolution law of first decreasing and then increasing, while the correlation dimension corresponding to the ringing count signal shows an overall evolution law of first increasing and then decreasing. The results indicate that the phase trajectory volume, correlation dimension, and crack changes have a consistent dynamic change. Therefore, the phase trajectory and correlation dimension are effective tools to describe the pore change characteristics of rock combinations. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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15 pages, 7611 KiB  
Article
Experimental Study on the Impact of High-Frequency Vibration Excitation on Coal Fracturing
by Lei Zhang, Xufeng Wang and Zhijun Niu
Fractal Fract. 2024, 8(9), 546; https://doi.org/10.3390/fractalfract8090546 - 19 Sep 2024
Viewed by 954
Abstract
The ultrasonic vibration rock-breaking method has been successfully applied to hard rock due to its high efficiency and controllable energy, providing a novel approach for the development of a more efficient, intelligent, safe, and environmentally friendly reconstruction method for coal and rock reservoirs. [...] Read more.
The ultrasonic vibration rock-breaking method has been successfully applied to hard rock due to its high efficiency and controllable energy, providing a novel approach for the development of a more efficient, intelligent, safe, and environmentally friendly reconstruction method for coal and rock reservoirs. By subjecting the rock to ultra-high frequency (>15 kHz) vibration load, rapid fatigue damage can be induced within a short period of time, thereby enhancing the extent of cracking in hard rock. In order to investigate the impact of high-frequency vibration excitation on coal cracking, this study conducted exploratory tests using an independently designed ultrasonic vibration excitation system. These tests were combined with nuclear magnetic resonance (NMR) and permeability measurements to compare and analyze the pore fracture structure and permeability changes in coal samples under resonant and non-resonant conditions. Additionally, multifractal characteristics of the coal samples were investigated. The results demonstrate that high-frequency vibration excitation leads to significant expansion of micropores and mesopores in coal samples. Moreover, there is a strong exponential relationship between coal porosity/permeability and excitation time. After 40 s of stimulation, both porosity and permeability increase by 32.4% and over 8400%, respectively; these increases are five times higher for resonance-state compared to non-resonance-state conditions. Furthermore, water-saturated coal samples exhibit multifractal characteristics in their NMR T2 spectrum distribution, and multifractal parameters ΔD(q)and Δα show positive correlations with the proportion of mesoporous/macropores but negative correlations with the proportion of micropores; conversely, Δf shows an opposite trend relative to pore proportions. The pore structure of coal exhibits intricate multi-scale characteristics, and the heterogeneity at various scales is quantified through multifractal analysis. This study confirms the feasibility of utilizing high-frequency vibration excitation for cracking coal rocks while also providing valuable insights for further expanding its application. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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21 pages, 62211 KiB  
Article
Damage Law and Reasonable Width of Coal Pillar under Gully Area: Linking Fractal Characteristics of Coal Pillar Fractures to Their Stability
by Zhaopeng Wu, Yunpei Liang, Kaijun Miao, Qigang Li, Sichen Liu, Qican Ran, Wanjie Sun, Hualong Yin and Yun Ma
Fractal Fract. 2024, 8(7), 407; https://doi.org/10.3390/fractalfract8070407 - 11 Jul 2024
Cited by 4 | Viewed by 1042
Abstract
The coal pillar is an important structure to control the stability of the roadway surrounding rock and maintain the safety of underground mining activities. An unreasonable design of the coal pillar size can result in the failure of the surrounding rock structure or [...] Read more.
The coal pillar is an important structure to control the stability of the roadway surrounding rock and maintain the safety of underground mining activities. An unreasonable design of the coal pillar size can result in the failure of the surrounding rock structure or waste of coal resources. The northern Shaanxi mining area of China belongs to the shallow buried coal seam mining in the gully area, and the gully topography makes the bearing law of the coal pillar and the development law of the internal fracture more complicated. In this study, based on the geological conditions of the Longhua Mine 20202 working face, a PFC2D numerical model was established to study the damage characteristics of coal pillars under the different overlying strata base load ratios in the gentle terrain area and the different gully slope sections in the gully terrain area, and the coal pillar design strategy based on the fractal characteristics of the fractures was proposed to provide a reference for determining the width of the coal pillars in mines under similar geological conditions. The results show that the reliability of the mathematical equation between the overlying strata base load ratio and the fractal dimension of the fractures in the coal pillar is high, the smaller the overlying strata base load ratio is, the greater the damage degree of the coal pillar is, and the width of the coal pillar of 15 m under the condition of the actual overlying strata base load ratio (1.19) is more reasonable. Compared with the gentle terrain area, the damage degree of the coal pillar in the gully terrain area is larger, in which the fractal dimension of the fracture in the coal pillar located below the gully bottom is the smallest, and the coal pillar in the gully terrain should be set as far as possible to make the coal pillar located below the gully bottom, so as to ensure the stability of the coal pillar. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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24 pages, 16242 KiB  
Article
Investigation into the Failure Characteristics and Mechanism of Rock with Single Elliptical Defects under Ultrasonic Vibrations
by Zhijun Niu, Xufeng Wang, Lei Zhang, Jiyao Wang, Zechao Chang, Chenlong Qian and Xuyang Chen
Fractal Fract. 2024, 8(5), 261; https://doi.org/10.3390/fractalfract8050261 - 27 Apr 2024
Cited by 3 | Viewed by 1212
Abstract
In order to investigate the effects of elliptical defects on rock failure under ultrasonic vibrations, ultrasonic vibration tests and PFC2D numerical simulations were conducted on rocks with single elliptical defects. The research results indicated that the fracture fractal dimension, axial strain, and [...] Read more.
In order to investigate the effects of elliptical defects on rock failure under ultrasonic vibrations, ultrasonic vibration tests and PFC2D numerical simulations were conducted on rocks with single elliptical defects. The research results indicated that the fracture fractal dimension, axial strain, and crack depth of specimens with elliptical defects at 45° and 90° were the smallest and largest, respectively. The corresponding strain and fractal dimension showed a positive linear and logarithmic function relationship with time. The maximum crack depth of 46.50 mm was observed on the specimens with an elliptical defect angle of 90°. Specimens with elliptical defects at 0°, 30°, 75°, and 90° exhibited more dense and frequent acoustic emission events than those with elliptical defects at 15°, 45°, and 60°. During the ultrasonic vibration process, the maximum total energy (87.86 kJ) and energy consumption coefficient (0.963) were observed on specimens with elliptical defect angles of 30° and 45°, respectively. The difference in the stress field led to varying degrees of plastic strain energy in the specimens, resulting in different forms of crack propagation and triggering differential acoustic emission events, ultimately leading to specimen failure with different crack shapes and depths. The fractal dimensions of elliptical defect specimens under ultrasonic vibration have a high degree of consistency with the changes in axial strain and failure depth, and the fractal dimension of defect specimens is positively correlated with the degree of failure of defect specimens. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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14 pages, 5303 KiB  
Article
Pore-Type-Dependent Fractal Features of Shales and Implications on Permeability
by Qian Zhang, Yanhui Dong and Shaoqing Tong
Fractal Fract. 2023, 7(11), 803; https://doi.org/10.3390/fractalfract7110803 - 4 Nov 2023
Cited by 2 | Viewed by 1791
Abstract
Pore structure features govern the capacity of gas storage and migration in shales and are highly dependent on the types of pores, i.e., interparticle (InterP) pores, intraparticle (IntraP) pores and organic matter (OM)-hosted pores. However, fractal features in terms of pore types and [...] Read more.
Pore structure features govern the capacity of gas storage and migration in shales and are highly dependent on the types of pores, i.e., interparticle (InterP) pores, intraparticle (IntraP) pores and organic matter (OM)-hosted pores. However, fractal features in terms of pore types and their respective contributions to permeability have been rarely addressed. On the basis of high-resolution imaging, fractal dimensions (Ds) have been determined from both pore size distributions and digital rock to quantify the heterogeneity in pore morphology and spatial textures. Overall, OM-hosted pores are smaller in size and more abundant in quantity, corresponding to a relatively high D, while IntraP pores are mainly isolated and scarce, translating into lower D values. Additionally, crack-like InterP pores with a moderate level of porosity and the D can play a pivotal role in shale seepage potential. A comparison of the estimated permeability among different pore types highlights that the contribution of interconnected OM pores to the overall permeability remains constrained unless they can link neighboring pore clusters, as commonly observed in organo-clay composites. Furthermore, the pore morphology and fractal features of shale rocks can exhibit noteworthy variations subjected to sedimentology, mineralogy, diagenesis and OM maturation. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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17 pages, 7599 KiB  
Article
Evolution Law of Shallow Water in Multi-Face Mining Based on Partition Characteristics of Catastrophe Theory
by Yujiang Zhang, Bingyuan Cui, Yining Wang, Shuai Zhang, Guorui Feng and Zhengjun Zhang
Fractal Fract. 2023, 7(11), 779; https://doi.org/10.3390/fractalfract7110779 - 26 Oct 2023
Cited by 23 | Viewed by 1661
Abstract
It is of great significance for ecological environment protection to clarify the regional evolution characteristics of shallow water under the disturbance of multi-working face mining. In this paper, the catastrophe theory method, GIS spatial analysis function and FEFLOW numerical calculation method were comprehensively [...] Read more.
It is of great significance for ecological environment protection to clarify the regional evolution characteristics of shallow water under the disturbance of multi-working face mining. In this paper, the catastrophe theory method, GIS spatial analysis function and FEFLOW numerical calculation method were comprehensively used to study the instability risk and evolution law of shallow water systems in the Zhuan Longwan Coal Mine. The results show that: the Zhuan Longwan Coal Mine is divided into five areas (small risk area, light risk area, middle risk area, heavy risk area and special risk area) based on catastrophe theory, among which the middle risk area has the largest area of 16,616,880 m2, and the special risk area has the smallest area of 1,769,488 m2. Based on the results of catastrophe zoning, the evolution law of shallow water under multi-surface disturbance in different zones is expounded. In the middle-risk area, the water level drop at measuring point 4 is the largest, which is 0.525 m, and the water level drop at measuring point 5 is the smallest, which is 0.116 m. The study aims to provide a basis for regional coal development planning and research on the method of water-retaining coal mining. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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20 pages, 7668 KiB  
Article
Study on Uniaxial Compression Deformation and Fracture Development Characteristics of Weak Interlayer Coal–Rock Combination
by Shun Lei, Dingyi Hao and Shuwen Cao
Fractal Fract. 2023, 7(10), 731; https://doi.org/10.3390/fractalfract7100731 - 2 Oct 2023
Cited by 7 | Viewed by 1867
Abstract
With increases in mining depth and intensity, disasters such as stress concentration, slab failure, and coal body dynamic outbursts at the coal–rock interface have become more serious. Therefore, it is important to analyze the stress–strain behavior of coal–rock combinations to explore the deterioration [...] Read more.
With increases in mining depth and intensity, disasters such as stress concentration, slab failure, and coal body dynamic outbursts at the coal–rock interface have become more serious. Therefore, it is important to analyze the stress–strain behavior of coal–rock combinations to explore the deterioration process and failure characteristics of coal–rock combinations. In this study, we used field survey, theoretical analysis, and numerical simulation methods to explore the microstructure characteristics of the coal–rock interface and the influence of interlayer thickness on the composite body. The results show that with the increase in interlayer thickness, the compressive strength of the composite body gradually decreases. This reduction is mainly due to the interlayer dividing the coal sample, resulting in a decrease in the equivalent elastic modulus of the composite body, weakening of the overall integrity, and a decrease in carrying capacity. In addition, the failure mode and mechanical properties of the coal–rock combination are influenced by the interlayer position. Different “soft layer” positions can lead to changes in the overall carrying and failure modes of the coal–rock composite. The position of the interlayer also has a significant influence on the failure mode and fracture propagation of the composite body. This study provides an important theoretical reference for the control of coal–rock deformation and instability and regional rock mass modification in underground engineering. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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15 pages, 9271 KiB  
Article
Fractal Characteristics of Overburden Rock Fractures and Their Impact on Ground Fissures in Longwall Coal Mining
by Chunwei Ling, Bin Liu, Cun Zhang, Teng Teng, Kangning Zhang, Bo Sun and Jinlong Zhou
Fractal Fract. 2023, 7(10), 699; https://doi.org/10.3390/fractalfract7100699 - 23 Sep 2023
Cited by 3 | Viewed by 1569
Abstract
Ground fissures are generated during the coal mining process due to overlying strata migration, which provides gas and water seepage channels and usually contributes to coal mining accidents in shallow buried coal seams with larger mining height working faces. Thus, the evolution features [...] Read more.
Ground fissures are generated during the coal mining process due to overlying strata migration, which provides gas and water seepage channels and usually contributes to coal mining accidents in shallow buried coal seams with larger mining height working faces. Thus, the evolution features of ground fissures in large mining height working faces and shallow buried coal seams were explored by considering field observation data, similar simulation, and numerical simulations. The results show that the weathered rock layer above the thin bedrock inhibits fracture growth caused by coal mining. Overlying strata fracture expansion can be quantitatively divided into three stages based on fractal dimension: the overburden fracture formation stage, the overburden deformation fracture expansion stage, and the overburden fracture stable development stage. The movement deformation region of the ground fissure can be described by three characteristic zones: the boundary tension zone, the central compression zone, and the central dynamic tension and compression zone. Central dynamic fissures usually have 3–5 fissure counts with 2–5 m intervals between each group of fissures; central fissures develop twice from open to closed widths; the time period for two central fissures to reach their with maximum widths is 11–20 days; and border fissures expand rapidly with maximum values in a time period of 5–6 days. Full article
(This article belongs to the Special Issue Applications of Fractal Analysis in Underground Engineering)
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