Energy Evolution of Coal at Different Depths Under Unloading Conditions

Jia, Zheqiang; Li, Cunbao; Zhang, Ru; Wang, Man; Gao, Mingzhong; Zhang, Zetian; Zhang, Zhaopeng; Ren, Li; Xie, Jing

doi:10.1007/s00603-019-01856-y

Cited by 54 publications

(25 citation statements)

References 10 publications

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“…Sliding friction between the fracture planes dissipates energy, and the generation of new fracture planes requires energy absorption, which means that the failure and damage of coal specimens is a process of energy accumulation, dissipation, and release [51][52][53]. The changes in stress and energy of coal specimens are shown in Figure 11 [54][55][56][57].…”

Section: Effect Of Loading Rate On Energy Dissipation and Releasementioning

confidence: 99%

Loading Rate and Bedding Plane Coupled Effect Study on Coal Failure under Uniaxial Compression: Acoustic Emissions and Energy Dissipation Analysis

et al. 2022

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The mechanical behavior of coal is significantly influenced by the loading rate and bedding plane. In this paper, the uniaxial compression tests at different loading rates were conducted on coal specimens with vertical bedding (CSVB) and coal specimens with parallel bedding (CSPB), which were prepared by the coal with bursting liability from the Ordos deep mining areas, China. The results show that the uniaxial compressive strengths of CSVB and CSPB are positively correlated with the loading rate. The peak values of acoustic emission (AE) counts and accumulated absolute AE energy of CSVB and CSPB increase with the loading rate, and the AE parameters of CSVB are larger than those of CSPB. The variation rules of input energy density and elastic energy density are similar for CSVB and CSPB, but the variation rules of dissipated energy density in stage IV are different. As the axial load increases, the energy storage rate and energy dissipation rate of both coal specimen types increase and decrease, respectively. The bedding planes of coal and the loading conditions in the field should be fully considered when identifying the bursting liability of coal and forecasting coal burst. This study can provide a reference for coal burst warning and prevention under similar geological conditions in Ordos deep mining areas.

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Section: Effect Of Loading Rate On Energy Dissipation and Releasementioning

confidence: 99%

Loading Rate and Bedding Plane Coupled Effect Study on Coal Failure under Uniaxial Compression: Acoustic Emissions and Energy Dissipation Analysis

et al. 2022

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“…For the convenience of calculation, the elastic energy U e is properly simplified. e energy of each part of the rock element in the principal stress space can be expressed as follows [28]:…”

Section: E Energy Evolution Of Sandstone Under Uniaxial Loading-unloading Conditionsmentioning

confidence: 99%

“…In fact, the stresses in rock masses are constantly adjusting with mining at different depths [27][28][29][30], resulting in complex stress loading and unloading processes, rock mass damage accumulation, and significant mining-induced deformation and damage, which seriously affect crack propagation and distribution in mining-induced coal and rocks [31]. Xie et al [32] explored the distribution law of the abutment pressure in a coal seam, analyzed the mining dynamic characteristics of the peak value and position of the abutment pressure in front of the working face under the influence of mining, obtained the dynamic stress conditions due to mining of the coal body in front of the working face, and further carried out experimental research on the dynamic behavior of rock during coal mining.…”

Section: Introductionmentioning

confidence: 99%

The Ultrasonic P‐Wave Velocity‐Stress Relationship and Energy Evolution of Sandstone under Uniaxial Loading‐Unloading Conditions

Zhang

et al. 2021

Advances in Materials Science and Engineering

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As shallow resources are exhausted, deep resources are gradually being exploited; consequently, mining disasters and accidents have increased significantly over time. During mining, a deep rock mass experiences complex mining-induced stress evolution, damage accumulation, and deformation failure processes, and the mechanical and acoustic properties of the rock constantly change. To better understand the variation in the mechanical and acoustic properties of rock under loading and unloading conditions, uniaxial loading-unloading experiments with real-time ultrasonic P-wave velocity monitoring were conducted on sandstone specimens drilled from a coal seam roof. The test results show that the axial stress level is directly related to the P-wave velocity. A logarithmic relationship exists between the ultrasonic P-wave velocity and stress in the tested sandstones. The wave velocity increase caused by the unit axial pressure increase is significantly lower than that at the initial loading stage after entering the higher stress level. The energy evolution of sandstone during loading and unloading is closely related to the stress loading history and reflects the damage accumulation in the rock. Under elastic loading, the energy accumulation is mainly reflected by an increase in elastic energy, and less energy is dissipated during the elastic loading period. Stress unloading causes high energy dissipation, resulting in irreversible strain and damage accumulation, which provides a good basis for using ultrasonic testing to preliminarily judge the failure of a specific rock and formulate corresponding engineering measures.

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“…According to this, the initial confining pressures of the coal samples at burial depths of 300 m, 600 m, 850 m, and 1050 m in the Pingdingshan coal mine area were 14.2 MPa, 31.3 MPa, 40.7 MPa, and 43.6 MPa, respectively. Referring to the generalization method of the mining stress path by Xie et al [32,33], the experimental process was divided into three stages: the hydrostatic pressure stage, the first unloading stage, and the second unloading stage (as shown in Figure 3).…”

Section: Testing Programmentioning

confidence: 99%

“…Accordingly, the evolution path of mining disturbance unloading stress experienced by coal near the working face was simulated, and the testing program of coal samples at different depths is shown in Table 1. [32,33], the experimental process was divided into three stages: the hydrostatic pressure stage, the first unloading stage, and the second unloading stage (as shown in Figure 3).…”

Section: Testing Programmentioning

confidence: 99%

Failure Behavior and Damage Characteristics of Coal at Different Depths under Triaxial Unloading Based on Acoustic Emission

Zhang

Gao

et al. 2020

Energies

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The depth effect of coal mechanical behavior seriously affects the safety and efficiency of deep coal mining. To explore the differences in failure behavior and damage characteristics of coal masses at different depths during the coal mining process, based on the consideration of in situ stress environment, physical properties, and mining disturbance of coal seams, triaxial unloading experiments with acoustic emission (AE) monitoring were conducted on coal samples at four different depths taken from the Pingdingshan coal mine area. The results showed that the AE activity of deep coal was more concentrated, and the cumulative AE energy of coal increased with increasing depth. The cumulative AE energy of the 1050-m coal sample was 69 times that of the 300-m coal sample. The b value representing the microcrack scale decreased with increasing depth, and the rupture degree of deep coal increased. The cracking mode of coal was classified and the failure behavior was analyzed. The cumulative tensile crack percentage of coal increased with increasing depth, and the tensile–shear composite failure occurred in the 300-m coal sample, whereas significant tensile failure occurred in the 1050-m coal sample. In addition, the damage evolution process of coal was divided into three stages, and the characteristic stress of coal was obtained. The ratio of crack initiation stress (σci) to peak stress (σc) increased with increasing depth, and the damage evolution process of deep coal was more rapid. The research results can provide useful guidance for disaster prevention and evaluation of surrounding rock stability during deep coal resource mining in the Pingdingshan coal mine area.

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Energy Evolution of Coal at Different Depths Under Unloading Conditions

Cited by 54 publications

References 10 publications

Loading Rate and Bedding Plane Coupled Effect Study on Coal Failure under Uniaxial Compression: Acoustic Emissions and Energy Dissipation Analysis

Loading Rate and Bedding Plane Coupled Effect Study on Coal Failure under Uniaxial Compression: Acoustic Emissions and Energy Dissipation Analysis

The Ultrasonic P‐Wave Velocity‐Stress Relationship and Energy Evolution of Sandstone under Uniaxial Loading‐Unloading Conditions

Failure Behavior and Damage Characteristics of Coal at Different Depths under Triaxial Unloading Based on Acoustic Emission

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