Microscopic Damage Mechanism of Coal Sample Under Uniaxial Compression Test Under Different Creep Pre-damage

Purpose The purpose of this paper is to obtain the mechanical behavior and damage mechanism of the coal and rock near the stope under the stress state and stress paths of the surrounding rock with the dynamic mining. Design/methodology/approach Through the three-axial compression test and the uniaxial compression test by meso experiment device, the mechanical behavior and fracture evolution process of coal and rock were studied, and the acoustic emission (AE) characteristics under uniaxial compression of the coal and rock were contrasted. Findings Under the three-axial compression, the strength of coal and rock enhance significantly by confining pressure. The volume of outburst coal shows obvious stages: compression is followed by expansion. The coal first appear to undergo compaction under vertical stress due to volume decrease, but with the development of micro- and macro-cracks, the specimens appeared to expand; under the uniaxial compression, through the comparison of stress–strain relationship and the crack propagation process, stress drop and fracture of coal have obvious correlation. The destruction of coal was gradual due to the slow and steady accumulation of internal damage. Due to the influence of the end effect, the specimens show the “conjugate double shear failure”. The failure process of the coal and rock and the characteristics of the AEs have a corresponding relationship: the failure causes a large number of AE events. Before the events peak, there was an initial stage, calm growth stage and explosive growth stage. There were some differences between the rock and coal in the characteristics of the AE. Originality/value These research studies are conducted to provide guidance on the basis of mine disaster prevention and control.

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Strength and Microscopic Damage Mechanism of Yellow Sandstone with Holes under Freezing and Thawing

Advances in Civil Engineering ◽

10.1155/2020/5921901 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13 ◽

Cited By ~ 1

Author(s):

Huren Rong ◽

Jingyu Gu ◽

Miren Rong ◽

Hong Liu ◽

Jiayao Zhang ◽

...

Keyword(s):

Mechanical Properties ◽

Pore Size ◽

Power Function ◽

Damage Mechanism ◽

Uniaxial Compression Test ◽

Freezing And Thawing ◽

Freeze Thaw ◽

Thaw Cycle ◽

Freeze Thaw Cycle ◽

Microscopic Damage

In order to study the damage characteristics of the yellow sandstone containing pores under the freeze-thaw cycle, the uniaxial compression test of saturated water-stained yellow sandstones with different freeze-thaw cycles was carried out by rock servo press, the microstructure was qualitatively analyzed by Zeiss 508 stereo microscope, and the microdamage mechanism was quantitatively studied by using specific surface area and pore size analyzer. The mechanism of weakening mechanical properties of single-hole yellow sandstone was expounded from the perspective of microstructure. The results show the following. (1) The number of freeze-thaw cycles and single-pore diameter have significant effects on the strength and elastic modulus of the yellow sandstone; the more the freeze-thaw cycles and the larger the pore size, the lower the strength of the yellow sandstone. (2) The damage modes of the yellow sandstone containing pores under the freeze-thaw cycle are divided into five types, and the yellow sandstone with pores is divided into two areas: the periphery of the hole and the distance from the hole; as the number of freeze-thaw cycles increases, different regions show different microscopic damage patterns. (3) The damage degree of yellow sandstone is different with freeze-thaw cycle and pore size. Freeze-thaw not only affects the mechanical properties of yellow sandstone but also accelerates the damage process of pores. (4) The damage of the yellow sandstone by freeze-thaw is logarithmic function, and the damage of the yellow sandstone is a power function. The damage equation of the yellow sandstone with pores under the freezing and thawing is a log-power function nonlinear change law and presents a good correlation.

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A New Apparatus for Installing Distributed Optical Sensors onto Uniaxial Compression Test Specimens to Measure Full-Field Strain Responses

Geotechnical Testing Journal ◽

10.1520/gtj20210021 ◽

2021 ◽

Vol 45 (1) ◽

pp. 20210021

Author(s):

Shawn Hegger ◽

Nicholas Vlachopoulos ◽

Mark S. Diederichs

Keyword(s):

Uniaxial Compression ◽

Compression Test ◽

Optical Sensors ◽

Field Strain ◽

Uniaxial Compression Test ◽

Full Field ◽

New Apparatus ◽

Strain Responses

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Observation and Evaluation of Microcrack Propagation in Granite Fractured by Uniaxial Compression Test Using Fluorescent Resins.

Journal of the Society of Materials Science Japan ◽

10.2472/jsms.44.851 ◽

1995 ◽

Vol 44 (502) ◽

pp. 851-855 ◽

Cited By ~ 3

Author(s):

Hiromu KUSUDA ◽

Takashi NISHIYAMA ◽

Toshiaki SAITO

Keyword(s):

Uniaxial Compression ◽

Compression Test ◽

Uniaxial Compression Test ◽

Microcrack Propagation

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End Effect in Uniaxial Compression Test of Marble

Science Discovery ◽

10.11648/j.sd.20190706.17 ◽

2019 ◽

Vol 7 (6) ◽

pp. 415

Author(s):

Wu Zhichou ◽

Zhang Ning ◽

Wang Jiabo ◽

Wang Shuo

Keyword(s):

Uniaxial Compression ◽

Compression Test ◽

Uniaxial Compression Test ◽

End Effect

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Evaluation Method of Granite Multiscale Mechanical Properties Based on Nanoindentation Technology

Geofluids ◽

10.1155/2021/6745900 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Man Lei ◽

Fa-ning Dang ◽

Haibin Xue ◽

Mingming He

Keyword(s):

Mechanical Properties ◽

Elastic Modulus ◽

Uniaxial Compression ◽

Compression Test ◽

Evaluation Method ◽

Poisson Ratio ◽

Nanoindentation Test ◽

Uniaxial Compression Test ◽

Displacement Curve ◽

Mineral Contents

In order to study the mechanical properties of granite at the micro- and nanoscale, the load-displacement curve, residual indentation information, and component information of the quartz, feldspar, and mica in granite were obtained using a nanoindentation test, a scanning electron microscope (SEM), and X-ray diffraction (XRD). The elastic modulus and the hardness of each component of the granite were obtained through statistical analysis. Treating rock as a composite material, the relation between the macro- and microscopic mechanical properties of rock was established through the theory of micromechanical homogenization. The transition from micromechanical parameters to macromechanical parameters was realized. The equivalent elastic modulus and Poisson’s ratio of the granite were obtained by the Self-consistent method, the Dilute method, and the Mori-Tanaka method. Compared with the elastic modulus and the Poisson ratio of granites measured by a uniaxial compression test and the available data, the applicability of the three methods were analyzed. The results show that the elastic modulus and hardness of the quartz in the granite is the largest, the feldspar is the second, the mica is the smallest. The main mineral contents in granite were analyzed using the semiquantitative method by XRD and the rock slice identification test. The elastic modulus and the Poisson ratio of granite calculated by three linear homogenization methods are consistent with those of the uniaxial compression test. After comparing the calculation results of the three methods, it is found that the Mori-Tanaka method is more suitable for studying the mechanical properties of rock materials. This method has an important theoretical significance and practical value for studying the quantitative relationship between macro- and micromechanical indexes of brittle materials. The research results provide a new method and an important reference for studying the macro-, micro-, and nanomechanical properties of rock.

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