Change of the mode of failure by interface friction and width-to-height ratio of coal specimens

Rashed, Gamal; Peng, Syd S.

doi:10.1016/j.jrmge.2015.03.009

Cited by 18 publications

(7 citation statements)

References 1 publication

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“…Figure 4 shows that the strain and stress increased as the compression loading was applied and then decreased suddenly. And, the compression failure process of the coal cores can be divided into four stages, which is similar to the findings of Rashed and Peng [37].…”

Section: Static Mechanical Properties Of Coalsupporting

confidence: 71%

Experimental Investigation on the Mechanical Response of Coals to Uniaxial Compression and Low‐Speed Dynamic Loading

Zhu

Ren

et al. 2021

Shock and Vibration

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The surrounding rock of roadways in underground coal mines will lose its stability or even collapse under gas explosions, especially roadways surrounded by coals. The dynamic mechanical properties of coals were tested in order to investigate the dynamic response of coals under gas explosions. The static mechanical properties of coals were also tested as comparison. It is found that the dynamic stress-strain curves showed no obvious pore compaction stage comparing with uniaxial loading. The dynamic compression strength and the elastic modulus are obviously larger than those obtained in the static mechanical properties test, and the dynamic strain shows an obvious hysteresis phenomenon. The ultimate strain and absorbed energy increased linearly with increase of the strain rate. With the increase of dynamic loading, the fragment size of coal cores decreased obviously. The results could provide a reference for the antiexplosion design of the coal roadway.

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Section: Static Mechanical Properties Of Coalsupporting

confidence: 71%

Experimental Investigation on the Mechanical Response of Coals to Uniaxial Compression and Low‐Speed Dynamic Loading

Zhu

Ren

et al. 2021

Shock and Vibration

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“…Localized fractures were concentrated near the sidewalls, as shown in Figure 6(c). Similar work on coal specimens [70] showed that the failure model also depends on interface friction.…”

Section: Fractures In the Chain Pillarmentioning

confidence: 73%

“…Small-scale laboratory tests are widely employed on coal measure samples to study mining-induced fractures and the associated mechanical and fluid behaviors. For example, cuboid coal samples under unconfined loading conditions are widely used to evaluate coal pillar strength and failure (or fracture) modes [69,70]. In laboratory tests, measurement systems can be well prepared in order to obtain high-quality experimental data.…”

Section: Outstanding Issuesmentioning

confidence: 99%

“…Mathey [69] performed a series of tests on coal-concrete samples to study the relationships between failure (fracture mode) and aspect ratios, which have been summarized in Section 3. Many uniaxial tests were conducted on coal samples at West Virginia University with different aspect ratios and interface frictions to determine how these parameters affected the failure mode of the samples [70,119]. It was found that interface friction has a significant effect on the failure mode, while the aspect ratio plays a secondary role.…”

Section: Outstanding Issuesmentioning

confidence: 99%

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A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

Bai

2019

Geofluids

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It is believed that underground longwall mining usually produces fractures in the surrounding rocks. On the one hand, mining-induced fractures not only degrade the strength of the rock mass but also serve as main channels for fluids (e.g., water and methane). Fractures facilitate the failure of the rock mass and fluid inrush into working spaces. Therefore, mining-induced fractures are significant for the safety evaluation of underground structures and finding feasible solutions. On the other hand, the fractures are also beneficial for methane collection and coal fragmentation, which are essential for the successful operation of longwall top coal caving mining. Therefore, determining the characteristics of induced fractures is significant for underground longwall mining. From a global perspective, longwall mining-induced fractures in the overburden have been well studied, which improves the understanding of the mining pressure and ground control. However, induced fractures near the longwall face, which have more significant effects on mining activities, have not been summarized. The goal of this review paper is to provide a general summary of the current achievements in characterizing mining-induced fractures in near-face regions. The characteristics of mining-induced fractures in the coal wall, chain pillar, immediate roofs and top coal, and floors are reviewed and summarized. Remarks are made on the current progress of, fundamental problems with, and developments in methodologies for characterizing mining-induced fractures using methods such as field observations, small-scale laboratory tests, physical modeling, and numerical modeling. Based on a comprehensive analysis, the advantages and disadvantages of each method are discussed, and the ideal conditions for applying each of these methods are also recommended.

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“…For lubricated rock specimen-steel platen contacts, it is reported that the µ values can be as low as 0.024 (He et al, 2014) and as high as 0.1 (Rashed and Peng, 2015), or even 0.39 in some cases (Hawkes and Mellor, 1970). A µ value of 0.05 is reported in Labuz and Bridell (1993) and a µ range of 0.04 ± 0.003 is given in the Handbook on Mechanical Properties of Rocks by Vutukuri et al (1974).…”

Section: Friction At Friction At Friction Atmentioning

confidence: 99%

Influence of end effect on rock strength in true triaxial compression test

Cai

Zhang

et al. 2017

Can. Geotech. J.

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The influence of the end effect on rock strength in true triaxial compression testing was studied using a numerical approach. The influence of the intermediate principal stress (σ2) on rock strength was isolated by using the two-dimensional Mohr–Coulomb failure criterion that depends only on the major principal stress (σ1) and minor principal stress (σ3). Thus, any enhancement to the rock strength with the increase of σ2 can be attributed to the end effect. It was shown that the end effect can result in an apparent σ2 effect, as long as the coefficient of friction (μ) at the rock specimen – steel platen contacts is not zero and the specimen in the σ2 loading direction is squat. When the strengthening due to the increase of σ2 predicted by a theoretical failure criterion was added to the strengthening due to the end effect, the results were in good agreement with the observed σ2 effect from some previous laboratory tests, indicating that the observed σ2 effect in true triaxial compression testing could be partially influenced by the end effect, particularly when σ3 was low. It is suggested to decrease the end effect to a level where the apparent σ2 effect is very small so that the obtained test results are more meaningful to characterize the actual σ2 effect.

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Change of the mode of failure by interface friction and width-to-height ratio of coal specimens

Cited by 18 publications

References 1 publication

Experimental Investigation on the Mechanical Response of Coals to Uniaxial Compression and Low‐Speed Dynamic Loading

Experimental Investigation on the Mechanical Response of Coals to Uniaxial Compression and Low‐Speed Dynamic Loading

A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

Influence of end effect on rock strength in true triaxial compression test

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