scholarly journals An Experimental Apparatus for Monitoring Radon during Compression of Coal/Rock Samples and Its Preliminary Application

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Wei Zhang ◽  
Kaidi Xie ◽  
Yanchao Zhu ◽  
Yandong Zhang ◽  
Xu Duan ◽  
...  
Keyword(s):  
Compressive Load ◽  
Future Research ◽  
Radon Emanation ◽  
Compression Tests ◽  
Rock Samples ◽  
Airtight Container ◽  
Experimental Apparatus ◽  
Coal Rock ◽  
Fractal Characteristics ◽  
Mathematical Equations

Based on the radionuclide distributions in sedimentary coal-bearing strata, this study analyzed the microrelease mechanisms of radon in coal-bearing strata. It was found that the microrelease process includes three stages: emanation, migration, and exhalation. Based on this, an experimental apparatus was independently designed for monitoring radon during compression of coal/rock samples from coal-bearing strata, whose major components include an electrohydraulic servocontrolled rock mechanics testing system, an airtight container, coal/rock samples, radon output device, and a continuous emanometer. The developed apparatus was preliminarily utilized for uniaxial compression tests on mudstone samples taken from the #21105 coalface of the Fourth Coal Mine in Yili Coalfield, China. The test results show that before sample failure under the uniaxial compressive load (UCL), the radon concentration is negatively correlated with the applied UCL and the magnitude of imposed elastic deformation. Increasing the applied load shortens the period of stable deformation, gradually decreasing the porosity of the rock, and as a result of declining the concentration of radon emanation from the rock. Finally, suggestions for future research are proposed, including mathematical equations to express the correlations between different experimental parameters and fractal characteristics of radon release from porous media.

scholarly journals Frictional sliding tests on combined coal-rock samples

2014 ◽  
Vol 6 (3) ◽  
pp. 280-286 ◽  
Author(s):  
Tao Wang ◽  
Yaodong Jiang ◽  
Shaojian Zhan ◽  
Chen Wang
Keyword(s):  
Frictional Sliding ◽  
Rock Samples ◽  
Coal Rock

EXPERIMENTAL INVESTIGATION ON MULTI-FRACTAL CHARACTERISTICS OF ACOUSTIC EMISSION OF COAL SAMPLES SUBJECTED TO TRUE TRIAXIAL LOADING–UNLOADING

Fractals ◽  
2020 ◽  
Vol 28 (05) ◽  
pp. 2050092 ◽  
Author(s):  
RAN ZHANG ◽  
JIE LIU ◽  
ZHANYOU SA ◽  
ZAIQUAN WANG ◽  
SHOUQING LU ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Dynamic Changes ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Coal Deformation ◽  
Coal Rock ◽  
True Triaxial Stress ◽  
Fractal Characteristics ◽  
Loading And Unloading ◽  
Precursory Information

Coal–rock dynamic disasters seriously threaten safe production in coal mines, and an effective early warning is especially important to reduce the losses caused by these disasters. The occurrence of coal–rock dynamic disasters is determined by mining-induced stress loading and unloading. Therefore, it is of great significance to analyze the precursory information of coal deformation and failure during true triaxial stress loading and unloading. In this study, the deformation and failure of coal samples subjected to true triaxial loading and unloading, including fixed axial stress and unloading confining stress (FASUCS), are experimentally investigated. Meanwhile, acoustic emission (AE) during the deformation of coal samples is monitored, and the multi-fractal characteristics of AE are analyzed. Furthermore, combined with the deformation and failure of coal samples, the precursory information of coal deformation and rupture during true triaxial stress loading and unloading is obtained. Finally, the relationship between multi-fractal characteristics and damage evolution of coal samples under FASUCS is discussed. The results show that the multi-fractal spectral widths of AE time series under the conditions of FASUCS with different initial confining stresses or unloading rates are quite different, but the dynamic changes of multi-fractal parameters [Formula: see text] and [Formula: see text] are similar. This indicates that the microscopic complexity of AE events of coal samples under different conditions of FASUCS differs, but the macroscopic generation mechanism of AE events has inherent uniformity. The dynamic changes of [Formula: see text] and [Formula: see text] can reflect the stress and damage degree of coal samples. The dynamic change process of [Formula: see text] well accords with the damage evolution process of coal samples. A gradual decrease of [Formula: see text] corresponds to a slow increase of damage, while a sharp increase of it corresponds to a rapid growth of damage. At the same time, the mutation point of damage curve at distinct stress difference levels shares the same variation trend with the [Formula: see text] mutation point. The change of [Formula: see text] can reflect the damage process of coal samples, which can be used as precursor information for predicting coal–rock rupture. The finding is of great significance for the early warning of coal–rock dynamic disasters.

PVCO Pipeline Performance Under Large Ground Deformation

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Brad P. Wham ◽  
Christina Argyrou ◽  
Thomas D. O'Rourke ◽  
Harry E. Stewart ◽  
Timothy K. Bond
Keyword(s):  
Polyvinyl Chloride ◽  
Large Scale ◽  
Ground Deformation ◽  
Load Capacity ◽  
Compressive Load ◽  
Soil Liquefaction ◽  
Compression Tests ◽  
Cross Sectional ◽  
Joint Rotation ◽  
Statistical Characterization

Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show that the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.

scholarly journals Investigation into the gas adsorption-loading coupling damage constitutive model of coal rock

2021 ◽  
Author(s):  
Zhongzhong Liu ◽  
Hanpeng Wang ◽  
Su Wang ◽  
Yang Xue ◽  
Chong Zhang
Keyword(s):  
Gas Adsorption ◽  
Coupling Effect ◽  
Influencing Factor ◽  
Failure Process ◽  
Damage Model ◽  
Strain Curve ◽  
In Situ Stress ◽  
Compression Tests ◽  
Damage And Failure ◽  
Coal Rock

Abstract Coal and gas outburst is the result of comprehensive action of in-situ stress, gas and mechanical properties of coal rock. The coupling effect of loading and gas adsorption eventually leads to the coal rock failure. Based on the principle of strain equivalence and considering the coupling effect of gas adsorption and stress loading, an adsorption-loading coupling damage model is established which breaks through the bottleneck of only considering single influencing factor. Taking briquette samples with controllable properties as the research object, uniaxial compression tests of coal rock at different gas adsorption pressures are carried out, and the model is verified based on the test results. The results of model calculation and tests show that the meso damage stage of coal body can well correspond to the macroscopic deterioration phenomenon and it is in good agreement with the stress-strain curve. It is proved that the model has good applicability and can accurately describe the damage and failure process of coal rock.

scholarly journals Investigation of Dynamic Mechanical Properties of Coal after Freeze-Thaw Cyclic Conditions

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Shuang Gong ◽  
Wen Wang ◽  
Furui Xi ◽  
Wenlong Shen
Keyword(s):  
Mechanical Properties ◽  
Rock Slope ◽  
Dynamic Mechanical Properties ◽  
Rock Mechanic ◽  
Cycle Times ◽  
Freeze Thaw ◽  
Dynamic Mechanical ◽  
Experimental Apparatus ◽  
Coal Rock ◽  
Water Saturated

Due to the extensive excavation of the mine pit, a special frozen rock slope is formed, which transforms the permafrost (coal rock) of certain thickness in the frozen state to the melting state. To evaluate the dynamic mechanical properties and deformation characteristics of coal under cyclic freeze-thaw conditions, freeze-thaw experiments with different cycle times were conducted. And the mechanical properties of coal under quasistatic and dynamic conditions were investigated by using GCTS multifunctional rock mechanic experimental apparatus and SHPB dynamic loading apparatus, respectively. The results show that with the increase of freeze-thawing times, mass of both water-saturated and dried coal samples gradually decreased, the postpeak becomes gentler, and the specimens show ductile damage characteristics. The damage of the coal samples changed more after 30 freeze-thaw cycles, when deterioration of the coal samples was highest. The elastic modulus of the coal sample after freeze-thawing decreases continuously with the increase of the number of freeze-thaw cycles, and its trend decreases approximately linearly. Dynamic compressive strength of the coal samples decreases after freeze-thaw cycles, and this trend is consistent with the quasistatic loading conditions.

PVCO Pipeline Performance Under Large Ground Deformation

2015 ◽  
Author(s):  
Brad P. Wham ◽  
Christina Argyrou ◽  
Thomas D. O’Rourke ◽  
Harry E. Stewart ◽  
Timothy K. Bond
Keyword(s):  
Polyvinyl Chloride ◽  
Large Scale ◽  
Ground Deformation ◽  
Load Capacity ◽  
Compressive Load ◽  
Soil Liquefaction ◽  
Compression Tests ◽  
Cross Sectional ◽  
Joint Rotation ◽  
Statistical Characterization

Technological advances have improved pipeline capacity to accommodate large ground deformation associated with earthquakes, floods, landslides, tunneling, deep excavations, mining, and subsidence. The fabrication of polyvinyl chloride (PVC) piping, for example, can be modified by expanding PVC pipe stock to approximately twice its original diameter, thus causing PVC molecular chains to realign in the circumferential direction. This process yields biaxially oriented polyvinyl chloride (PVCO) pipe with increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility. This paper reports on experiments performed at the Cornell University Large-Scale Lifelines Testing Facility characterizing PVCO pipeline performance in response to large ground deformation. The evaluation was performed on 150-mm (6-in.)-diameter PVCO pipelines with bell-and-spigot joints. The testing procedure included determination of fundamental PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture simulation. The test results show the performance of segmental PVCO pipelines under large ground deformation is strongly influenced by the axial pullout and compressive load capacity of the joints, as well as their ability to accommodate deflection and joint rotation. The PVCO pipeline performance is quantified in terms of its capacity to accommodate horizontal ground strain, and compared with a statistical characterization of lateral ground strains caused by soil liquefaction during the Canterbury earthquake sequence in New Zealand.

Study on Damage of Rock Samples with Single-Hole under Uniaxial Compression Condition

2012 ◽  
Vol 446-449 ◽  
pp. 3810-3813
Author(s):  
Bing Xie ◽  
Huai Feng Tong ◽  
Xiang Xia
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Compression Tests ◽  
Rock Samples ◽  
Single Hole ◽  
Compression Condition

Numerical specimens with single-hole is established by particle flow code PFC2D and uniaxial compression tests are conducted. Studies have shown that uniaxial compressive strength of specimen with single hole is less than complete specimens. As the holes move to the end of specimen, the uniaxial compressive strength first increases and then tends to decrease.

Research on the Charge Inducing Regularity of Coal Rock at Different Loading Rates in Uniaxial Compression Tests

2013 ◽  
Vol 56 (2) ◽  
pp. 196-202 ◽  
Author(s):  
PAN Yi-Shan ◽  
TANG Zhi ◽  
Li Zhong-Hua ◽  
ZHU Li-Yuan ◽  
LI Guo-Zhen
Keyword(s):  
Uniaxial Compression ◽  
Compression Tests ◽  
Loading Rates ◽  
Coal Rock

Strength Attenuation Law of Damaged Rock Samples and its Structure Effect

2013 ◽  
Vol 353-356 ◽  
pp. 602-607
Author(s):  
Hai Jian Su ◽  
Hong Wen Jing ◽  
Chen Wang ◽  
Bo Meng
Keyword(s):  
Uniaxial Compression ◽  
Axial Compression ◽  
Confining Pressure ◽  
Structure Effect ◽  
Thick Wall ◽  
Test Results ◽  
Compression Tests ◽  
Rock Samples ◽  
Nonlinear Fitting ◽  
Attenuation Value

In order to study the post-peak mechanics behavior of rock samples with a thick wall cylinder structure, damaged rock samples were precast with a new method. The uniaxial compression tests and tri-axial compression tests were conducted on the samples and the test results were compared with that of complete rock samples. The results show that strength attenuation value of the damaged samples increased with the confining pressure and the specific relationship was obtained by nonlinear fitting as (is the strength attenuation value and is the confining pressure); destructiveness of damaged samples was more serious than the complete ones; a new nearly horizontal failure phenomenon appeared under the tri-axial compression and it was more general with the increase of confining pressure. Structure effect of uniaxial strength attenuation was revealed based on the particle flow software system (PFC) and the corresponding theoretical model was found as (is the strength attenuation value under uniaxial compression of any damaged sample with a thick wall cylinder structure; is the strength attenuation value of standard damaged samples under uniaxial compression; is the structure ratio, and are the parameters of the material). Characteristic value of the strength attenuation value under uniaxial compression was obtained by calculation when the structure ratio was indefinitely large.

scholarly journals Analysis of Failure Characteristics and Strength Criterion of Coal-Rock Combined Body with Different Height Ratios

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Tuo Wang ◽  
Zhanguo Ma ◽  
Peng Gong ◽  
Ning Li ◽  
Shixing Cheng
Keyword(s):  
Shear Failure ◽  
Underground Mining ◽  
Triaxial Compression ◽  
Peak Stress ◽  
Strength Criterion ◽  
Confining Pressure ◽  
Experimental Results ◽  
Compression Tests ◽  
Rock Body ◽  
Coal Rock

In underground mining and roadway support engineering of coal mine, the coal and rock layers bear loads together; therefore, the deformation and mechanical characteristics of the coal-rock combined bodies are not the same as those of the pure coal or rock bodies. In this paper, conventional triaxial compression tests of coal-rock combined bodies with different height ratios were conducted. And the stress and deformation characteristics of coal-rock combined body were studied and the experimental results were analyzed with different strength criteria. The results show that the peak stress, elastic modulus, and strength reduction coefficient of coal-rock combined body are negatively correlated with the ratio of coal to coal-rock combination height and positively correlated with the confining pressure; the coal-rock combination shows obvious ductility under 10 MPa confining pressure. Under the conventional triaxial condition, the shear failure was the main cause of the lateral deformation of the coal body in the coal-rock combination, which was much larger than that of the rock body. The circle deformation value, volume strain value, and the deformation rate in the postpeak stage of coal-rock combination are much higher than those in the prepeak stage. Mohr–Coulomb and general Hoek–Brown strength criterion fit the experimental results well.

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