Effects of water content on mechanical failure behaviors of coal samples

Tang, Chun An; Yao, Qiangling; Chen, Tian; Shan, Changhao; Li, Jie

doi:10.1007/s40948-022-00382-6

Cited by 16 publications

(5 citation statements)

References 38 publications

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“…According to the relevant theories of hydrogeology, the forms of water in coal and rock voids usually include bound water, gravity water, and capillary water. Bound water is difficult to release before the temperature significantly increases, while gravity water and capillary water can evaporate at temperatures slightly higher than the evaporation temperature 61 . Assuming that the mass of a specimen after drying is m d and the mass of the specimen saturated with water is m s , the expression ω t for the saturation of the specimen after a certain watercontaining treatment is: where m t is the mass of the specimen after some treatment.…”

Section: Principles Of Water Absorption Designmentioning

confidence: 99%

Dynamic mechanical response and failure characteristics of coal and rock under saltwater immersion conditions

Sun,

Liu,

Jin

et al. 2024

Sci Rep

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The stability of coal and rock masses in water-rich mines is affected by both mine water erosion and dynamic disturbances. Thus, it is necessary to study the dynamic mechanical response and failure characteristics of coal and rock under the combination of saltwater and a high strain rate. To this end, a split Hopkinson pressure bar device was employed to investigate the effects of impact velocity, water content, and immersion liquid on the dynamic mechanical behaviours of coal and rock. The results revealed that the weakening effect of saltwater on the dynamic mechanical properties of coal and rock is much greater than that of distilled water. With increasing moisture content, the dynamic compressive strength of the coal specimens decreases monotonically, while that of the rock shows a trend of first increasing and then decreasing. The failure process and destruction of coal and rock are comprehensively affected by both the external impact load and the physical and mechanical properties of the material. The degree of damage of the coal and rock specimens increases with increasing impact velocity and water content. Moreover, the influence of various factors on the impact fracture mechanism of coal and rock under saltwater immersion conditions was revealed. These findings are highly important for the design and maintenance of underground coal and rock building structures.

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Section: Principles Of Water Absorption Designmentioning

confidence: 99%

Dynamic mechanical response and failure characteristics of coal and rock under saltwater immersion conditions

Sun,

Liu,

Jin

et al. 2024

Sci Rep

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“…Unlike conventional natural gas, CBM is primarily stored in coal reservoirs through adsorption [15]. As a special organic rock mass, coal reservoirs are featured with developed pore and cleat system [16,17], low mechanical strength [18,19], strong heterogeneity [20,21], etc. Meanwhile, coal reservoirs are very sensitive to pressure, temperature, and stress, leading to evident planar and vertical variations in CBM accumulation and development conditions [22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Geological Conditions Evaluation of Coalbed Methane of Dacun Block in the Guxu Mining Area, Southern Sichuan Coalfield

Zhu,

Zhang,

et al. 2024

Applied Sciences

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The geological conditions evaluation of coalbed methane (CBM) is of great significance to CBM exploration and development. The CBM resources in the Southern Sichuan Coalfield (SSC) of China are very abundant; however, the CBM investigation works in this area are only just beginning, and the basic geological research of CBM is seriously inadequate, restricting CBM exploration and development. Therefore, in this study, a representative CBM block (Dacun) in the SSC was selected, and the CBM geological conditions were evaluated based on field injection/fall-off well testing, gas content and composition measurements, and a series of laboratory experiments. The results show that the CH4 concentrations of coal seams in the Dacun Block, overall, take on an increasing trend as the depth increases, and the CH4 weathering zone depth is 310 m. Due to the coupled control of temperature and formation pressure, the gas content shows a “increase→decrease” trend as the depth increases, and the critical depth is around 700 m. The CBM is enriched in the hinge zone of the Dacun syncline. The moisture content shows a negative correlation with CBM gas content. The porosities of coal seams vary from 4.20% to 5.41% and increase with the Ro,max. The permeabilities of coal seams show a strong heterogeneity with values ranging from 0.001mD to 2.85 mD and present a decreasing trend with the increase in depth. Moreover, a negative relationship exists between coal permeability and minimum horizontal stress magnitude. The reservoir pressure coefficients are between 0.51 and 1.26 and show a fluctuation change trend (increase→decrease→increase) as the depth increases, reflecting that three sets of independent superposed gas-bearing systems possibly exist vertically in the Longtan Formation of the study area. The Langmuir volumes (VL) of coals range from 22.67 to 36.84 m3/t, indicating the coals have strong adsorptivity. The VL presents a parabolic change of first increasing and then decreasing with the increase in depth, and the turning depth is around 700 m, consistent with the critical depth of gas content. The gas saturations of coal seams are, overall, low, with values varying from 29.10% to 116.48% (avg. 68.45%). Both gas content and reservoir pressure show a positive correlation with gas saturation. The CBM development in the Dacun Block needs a large depressurization of reservoir pressure due to the low ratio (avg. 0.37) of critical desorption pressure to reservoir pressure.

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“…Acoustic emission (AE), also known as stress wave emission [1][2][3], refers to the deformation or crack propagation of the material locally under the action of external load or internal force; the transient strain energy generated during its failure process is rapidly released in the form of elastic waves [4,5]. Acoustic emission technology is an unconventional dynamic nondestructive testing method; with its unique dynamic and real-time detection performance [6], it can continuously monitor the internal damage and deformation of materials [7].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Acoustic Emission Characteristics of Granite and Sandstone under Uniaxial Compression

Sun

2023

Geofluids

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In order to better apply acoustic emission technology to engineering practice, this paper carried out indoor acoustic emission test, and uniaxial compression tests of granite and sandstone under monotonic loading and grading loading were carried out and monitored. The influencing factors of the acoustic emission characteristics of the two rock samples were discussed and the characteristics of the acoustic emission signals corresponding to different stages of rock failure were analyzed. The analysis of the test results includes the curve fitting relationship between the AE event count rate, energy rate, and stress time and the changes of AE event count rate and energy rate under different loading methods. The results of the study are as follows: there is a quiet zone in the acoustic emission event before the rock is destroyed and destabilized, and the higher the rock strength, the more obvious the quiet zone; this important feature can be used as a precursor feature of rock mass failure for prediction, and the rock acoustic emission energy rate is more obvious in the quiet area before destruction than the acoustic emission event rate; rock acoustic emission has experienced initial compaction zone, rising zone, peak zone, and descending zone, whether different rocks go through each stage and how long each stage lasts is related to the nature of the rock; under different loading methods, the failure mechanism of rock is different; the different loading rates of monotonic loading and grading loading will affect the change rate of acoustic emission.

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Effects of water content on mechanical failure behaviors of coal samples

Cited by 16 publications

References 38 publications

Dynamic mechanical response and failure characteristics of coal and rock under saltwater immersion conditions

Dynamic mechanical response and failure characteristics of coal and rock under saltwater immersion conditions

Geological Conditions Evaluation of Coalbed Methane of Dacun Block in the Guxu Mining Area, Southern Sichuan Coalfield

Experimental Study on Acoustic Emission Characteristics of Granite and Sandstone under Uniaxial Compression

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