Experimental Study on the Mechanical Behavior of Coal Samples during Water Saturation

Zhou, Kunyou; Li, Dou; Song, Shikang; Ma, Xiaotao; Chen, Bengang

doi:10.1021/acsomega.1c05077

Cited by 12 publications

(8 citation statements)

References 46 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

Section: Discussionmentioning

confidence: 99%

“…As a result, as illustrated in Figure 8, the pores widen, generating a variety of drainage channels, and the coal microstructure loosens or breaks. Water saturation softens the coal and considerably reduces its macro mechanical strength due to pore and microstructure changes [77]. Stress-strain curves under uniaxial loading of hard and brittle coals have a downward bulging tendency during the stage of compaction but rise rapidly at the peak point of stress.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Analytical Damage Model for Predicting Coal Failure Stresses by Utilizing Acoustic Emission

Ali

Wang

et al. 2023

Sustainability

View full text Add to dashboard Cite

Overburden collapse and water inrush in mines are primarily caused by rock fractures. Mining safety can be enhanced by monitoring and identifying early signs of coal failure in the mines. This article collected acoustic emission data synchronously throughout a series of uniaxial compression (UC) experiments on natural and water-saturated coal. The influence mechanisms of water, mechanical properties, and acoustic emission signals on the stress–strain curve and the SEM results of water-saturated and dry samples are investigated. As a result, the mechanical properties of coal are not only weakened by water saturation, such as elastic modulus, strain, stress, and compressive strength but also reduced acoustic emissions. In comparison with saturated coal, natural coal has a uniaxial stress of 13.55 MPa and an elastic modulus of 1.245 GPa, while saturated coal has a stress of 8.21 MPa and an elastic modulus of 0.813 GPa. Intergranular fractures are more likely to occur in coal with a high water content, whereas transgranular fractures are less likely to occur in coal with a high water content. An innovative and unique statistical model of coal damage under uniaxial loading has been developed by analyzing the acoustic emission data. Since this technique takes into account the compaction stage, models based on this technique were found to be superior to those based on lognormal or Weibull distributions. A correlation coefficient of greater than 0.956 exists between the piecewise constitutive model and the experimental curve. Statistical damage constitutive models for coal are compatible with this model. Additionally, the model can precisely forecast the stress associated with both natural and saturated coal and can be useful in the prevention of rock-coal disasters in water conditions.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Analytical Damage Model for Predicting Coal Failure Stresses by Utilizing Acoustic Emission

Ali

Wang

et al. 2023

Sustainability

View full text Add to dashboard Cite

show abstract

“…The water–rock interaction is considered an essential factor in deteriorating underground reservoir stability. The existing studies mainly focus on the relationship between the moisture content and parameters such as the uniaxial compressive strength, elastic modulus, and acoustic emission events of coal measure rocks after encountering water. − The mechanical performance of rocks was determined to decline with increased saturability by performing uniaxial shear and triaxial compression tests on rocks with different moisture contents. Macro- and meso-scale studies have also been conducted to assess the rock mechanics in response to varying pH, macroscopic fracture propagation, rock swelling, and fracture toughness .…”

Section: Introductionmentioning

confidence: 99%

Strength Degradation and Fracture Propagation of Repeatedly Immersed Artificial Dam Samples under Uniaxial Cyclic Loading–Unloading

et al. 2023

View full text Add to dashboard Cite

The use of underground reservoirs is a critical technique for achieving sustainable coal and water resources in many ecologically fragile mines in western China. Concrete samples subject to repeated water immersion and cyclic loading−unloading (CLU) operations were obtained from an underground artificial reservoir dam in Chahasu Colliery to study their strength damage and fracture propagation behavior. The variation in water content of the samples according to immersion times were divided into the rapid growth stage (0−10 h), slow growth stage (10−60 h), and stable stage (>60 h). With an increase in immersion times (IIT), the saturated water content of the coal samples logarithmically increased to 7.02%, and the ultrasonic wave velocity decreased by 10.44%. According to the increasing trend of plastic damage energy density, the total stress−strain curve was divided into four fracture stages. The total energy and elastic energy densities increased nonlinearly with the increase in cycles, whereas the plastic damage energy density first decreased and then increased. The plastic damage energy ratio at the stress peak point of the samples under different sequential times of immersion was 0.18, 0.29, 0.28, 0.58, and 0.61. The initial fracture development and fracture damage thresholds of the samples decreased by 20 and 50% with IIT, respectively. However, the proportion of the fracture closure and initial fracture development thresholds of the samples showed an increasing quadratic trend with IIT. Based on the low ratio of rise time to amplitude and high average frequency, the fracture mode of the samples under repeated water immersion was mainly tensile fracture. Acoustic emission events with energy higher than 10 4 aJ spread from the center with repeated water immersion. When the CLU was greater than 6, the plastic damage energy of the fitted three-dimensional surface increased nonlinearly with IIT. The energy parameter−plastic damage energy ratio was introduced to help develop a theoretical model for describing the complete stress−strain damage evolution of repeatedly immersed concrete samples under CLU. The paper provides technical references for improving the long-term strength design of concrete artificial dams of underground reservoirs.

show abstract

“…Water-bearing coal usually has lower uniaxial compressive strength (UCS), 24,25 shear strength, 26 and elastic modulus, 27,28 while greater the peak strain, 29 expanded pore sizes, 24 declined acoustic emission (AE) activities. 30 Mechanical properties of coal and rock material are loading approaches dependent. [31][32][33][34][35][36] Due to the roadway excavation and the rupture of the overlying rock layer occurring during the real coal mining process, 37,38 coal mass around mining areas is usually subject to various loading conditions, for instance, the stress impact, 39,40 stress concentration, 41,42 or stress relief.…”

Section: Introductionmentioning

confidence: 99%

“…The existence of water is generally considered to weaken the mechanical properties of coal. Water‐bearing coal usually has lower uniaxial compressive strength (UCS), 24,25 shear strength, 26 and elastic modulus, 27,28 while greater the peak strain, 29 expanded pore sizes, 24 declined acoustic emission (AE) activities 30 …”

Section: Introductionmentioning

confidence: 99%

Effect of water on the damage and energy dissipation feature of coal under uniaxial cyclic loading–unloading condition

Song,

Zhao,

et al. 2023

Energy Science & Engineering

View full text Add to dashboard Cite

To gain insight into the reduction mechanism of water on the dynamic destabilization failure character of coal under mining disturbance conditions, the effect of water on the damage and energy dissipation feature of coal was investigated via cyclic uniaxial compressive loading–unloading test, acoustic emission (AE) monitoring technology, and theoretical analysis. It manifests that the softening effect of water on the mechanical properties of coal is still remarkable, lower uniaxial compressive strength and elastic modulus, while greater axial strain and higher Poisson's ratio are observed under the cyclic loading–unloading condition. Water‐saturated specimens dissipate more energy during the cyclic loading–unloading process, which reduces the proportion of input energy accumulated in the coal mass, thus lowering the burst proneness of coal. A greater amount of damage generates in air‐dried specimens than that in water‐saturated specimens at the first cyclic loading–unloading cycle, while lower damage increments are observed in the following cycles. This may be the reason for the minimal energy dissipation of air‐dried specimens in the following cycles. The elastic modulus behaves logarithmically versus the increasing cyclic loading–unloading cycle counts. The energy dissipated due to the damage evolution and plastic deformation of coal specimens positively correlates with the energy released by AE activities, the AE energy in air‐dried specimens has a greater concentration around the peak axial stress and a stronger correlation with the dissipated energy. The cumulative AE energy and energy dissipation density are linearly correlated during the cyclic loading–unloading process, which indicates a possibility in estimating the damage evolution and the dynamic failure risk of coal via cumulative AE energy, under the cyclic loading–unloading condition.

show abstract

Experimental Study on the Mechanical Behavior of Coal Samples during Water Saturation

Cited by 12 publications

References 46 publications

Analytical Damage Model for Predicting Coal Failure Stresses by Utilizing Acoustic Emission

Analytical Damage Model for Predicting Coal Failure Stresses by Utilizing Acoustic Emission

Strength Degradation and Fracture Propagation of Repeatedly Immersed Artificial Dam Samples under Uniaxial Cyclic Loading–Unloading

Effect of water on the damage and energy dissipation feature of coal under uniaxial cyclic loading–unloading condition

Contact Info

Product

Resources

About