scholarly journals Investigation of Relation between Fracture Scale and Acoustic Emission Time-Frequency Parameters in Rocks

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Junwen Zhang
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fracture Process ◽  
Evaluation Model ◽  
Rock Fracture ◽  
Dominant Frequency ◽  
Time Frequency ◽  
Ae Energy ◽  
Emission Time ◽  
Fracture Scale

To investigate relation between fracture scale and acoustic emission time-frequency parameters in rocks, experiments of acoustic emission monitoring of granite uniaxial compression were carried out. The AE signal energy and dominant-frequency of granite fracture process were extracted by means of AE time-frequency analysis. The relation between fracture scale and AE time-frequency parameters (energy and frequency) in granite fracture process was analyzed. The evaluation model of rock fracture scale based on AE energy and dominant-frequency was established by using the intrinsic relation between the scale of rock fracture and the time-frequency parameters of rock mass. The evolution of crack scale in the process of uniaxial compression was analyzed based on the evaluation model of rock fracture scale. Results show that the AE energy and the dominant-frequency can reflect the crack scale inside the rock. The scale of rock fracture is proportional to the AE energy, which is inversely proportional to the AE dominant-frequency. Signals with low frequency and high energy usually represent large-scale cracks. On the contrary, if the high frequency has low energy value, it indicates a small-scale crack. The theory and method of evaluation of rock rupture scale based on AE time-frequency information (energy, frequency) can describe the failure process of rock crack scale variation characteristics. It provides a way and method for investigating the characterization of fracture size evolution process of rock fracture.

Time-Frequency Characteristic and Recognition Technology of Acoustic Emission Generated from Rock Brittle Fracture

2013 ◽  
Vol 405-408 ◽  
pp. 116-119
Author(s):  
Jian Wei Liu ◽  
Xian Zhen Wu ◽  
Xiang Xin Liu
Keyword(s):  
Neural Network ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Bp Neural Network ◽  
Rock Fracture ◽  
Strain Curve ◽  
Time Frequency ◽  
The Neural Network ◽  
Ae Signal ◽  
The Difference

To the instability of acoustic emission (AE) signal of rock fracture, the method about feature extraction and comprehensive recognition of those was came up with combining AE parameters, EMD and BP neural network. Through the acoustic emission experiment of different brittle rock under uniaxial compression, stress-strain curve and AE data were obtained; time-frequency characteristics of AE signal of rock samples were compared. Feature vectors, like AE parameters, and EMD energy entropy, was synthesized to BP neural network to distinguish different AE signal. The results show that evolution characteristic with stress or time of AE parameters of different rock which was under uniaxial compression exist similarities and differences. EMD and Welch spectrum can reflect the difference among spectrum, energy distribution of AE signal of different rock very well. With various characteristics of different rock acoustic emission, the neural network has good recognition effect.

Experimental Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

2012 ◽  
Vol 232 ◽  
pp. 24-27
Author(s):  
Zong Zhan Li ◽  
Jun Lin Tao ◽  
Yi Li
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Loading Rate ◽  
Testing Machine ◽  
Peak Stress ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

Test Research on Infrasound Wave of Granite Damage Course under Dynamic Uniaxial Compression

2011 ◽  
Vol 460-461 ◽  
pp. 692-697
Author(s):  
Shan Chai ◽  
Li Jun Li ◽  
Ze Qing Ju ◽  
Yue Zou ◽  
Yu Zeng Zhang
Keyword(s):  
Acoustic Emission ◽  
Data Analysis ◽  
Uniaxial Compression ◽  
Rock Fracture ◽  
Infrasonic Wave ◽  
Wave Emission ◽  
Compression Damage

More and more engineers apply AE (Acoustic Emission) to research rock fracture and damage. Infrasonic wave could be used to forecast earthquake, and structure earthquake is almost caused by rock compression damage, so in the course of rock fracture and damage, the infrasound wave emission could be researched in order to forecast earthquake. The granite specimens are compressed to damage. The infrasonic information in the course of compression are detected and collected. By means of data analysis, some principles of rock compression damage are found.

scholarly journals Acoustic Emission Multi-Parameter Analysis of Dry and Saturated Sandstone with Cracks under Uniaxial Compression

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1959 ◽  
Author(s):  
Hongru Li ◽  
Rongxi Shen ◽  
Dexing Li ◽  
Haishan Jia ◽  
Taixun Li ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fractured Rock ◽  
Rock Fracture ◽  
Failure Process ◽  
Parameter Analysis ◽  
Small Scale ◽  
Rock Interaction ◽  
Secondary Cracks ◽  
Ae Signals

In order to study the mechanics and acoustic emission (AE) characteristics of fractured rock under water-rock interaction, dried and saturated sandstone samples with prefabricated double parallel cracks were prepared. Then, uniaxial compression experiments were performed to obtain their AE signals and crack propagation images. The results show that water reduces the strength and fracture toughness of fractured sandstone and enhances plasticity. After saturation, the samples start to crack earlier; the cracks grow slowly; the failure mode is transformed from shear failure along the prefabricated cracks to combined shear and tensile failure; more secondary cracks are produced. The saturated samples release less elastic energy and weaker AE signals in the whole failure process. However, their AE precursor information is more obvious and advanced, and their AE sources are more widely distributed. Compared with dry specimens, the AE frequencies of saturated specimens in the early stage of loading are distributed in a lower frequency domain. Besides, the saturated samples release less complex AE signals which are dominated by small-scale signals with weaker multi-fractal characteristics. After discussion and analysis, it is pointed out that this may be because water makes rock prone to inter-granular fracture rather than trans-granular fracture. The water lubrication also may reduce the amplitude of middle-frequency band signals produced by the friction on the fracture surface. Multi-fractal parameters can provide more abundant precursory information for rock fracture. This is of great significance to the stability of water-bearing fractured rock mass and its monitoring, and is conducive to the safe exploitation of deep energy.

scholarly journals Failure behaviour and acoustic emission characteristics of different rocks under uniaxial compression

2019 ◽  
Author(s):  
Zhaohui Wang ◽  
Jiachen Wang ◽  
Shengli Yang ◽  
Lianghui Li ◽  
Meng Li
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Strain Hardening ◽  
Uniaxial Compression ◽  
Strength Increase ◽  
Evolutionary Trend ◽  
Sudden Increase ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Ae Energy

Abstract In the present study, mechanical behaviour of three types of rocks has been investigated under uniaxial compression. The stress–strain responses of the tested rocks are composed of four regions: the compaction stage; elastic stage; strain hardening stage and strain softening stage. The elastic modulus and uniaxial compressive strength increase in order from the result of the coal to the mudstone and then to the sandstone, while the Poisson ratio shows a reverse order. In coal and mudstone, volumetric dilation behaviour vanishes gradually with an increase in damage degree, while it remains stable in the sandstone where the strain hardening behaviour is less obvious. Regarding acoustic emission (AE) characteristics, AE hit and AE energy show a similar evolutionary trend in the loading process. A sudden increase in AE energy is accompanied with drastic drop or local fluctuation in the load-bearing capacity of the rock while AE hit fails in predicting such variation in the load-bearing capacity. A quiet stage of AE signal prior to the peak stress is captured, which can be taken as a precursor for rock failure. Failure pattern of the coal, mudstone and sandstone varies from shear faulting to tension-shear mixed fracturing and then to axial splitting, which is in good accordance with that deduced from AE location analysis.

scholarly journals Laboratory study on the propagation of edge cracks in rock-like material and its implication in coal mining

2021 ◽  
Vol 303 ◽  
pp. 01019
Author(s):  
Baoliang Zhang ◽  
Shichuan Zhang ◽  
Qingshuang Zhao
Keyword(s):  
Crack Initiation ◽  
Uniaxial Compression ◽  
Edge Crack ◽  
Longwall Mining ◽  
Rock Fracture ◽  
Water Inrush ◽  
Rock Masses ◽  
Tensile Cracks ◽  
Ae Energy ◽  
Secondary Cracks

Rock fracture propagation is a major hazard for mining and tunnel excavation in fractured rock masses or coal seams. A longwall mining panel with a typical dimension of 200m (width)×1000m (length)×3m (height) can be considered as an open edge crack. The fracturing processes in the vicinity of the edge crack (or the longwall panel) particularly in the roof and floor are critically important for the safety of mining operation because fracturing can lead to water inrush and dynamic loading on the working face. It’s therefore important to understand and predict the pre-existing edge crack initiation and propagation in rock masses. This paper describes a study investigating the mechanisms and pathways of rock fracture under uniaxial compression. In this study, a rock-like material which consists of model gypsum, water and diatomaceous earth at a mass ratio of 165:75:2 was used. The uniaxial compression strength of the material decreased with the increase of the length of pre-existing edge crack. During the tests, wing (tensile) cracks were first observed at the tip of the pre-existing edge crack. This was followed by secondary cracks as the loading increased. The final failure of the specimens however was dominated by tensile cracks throughout the specimens. Due to the sudden crack initiations in the specimens, the loading stress in the specimen varies stepwise, and acoustic emission (AE) energy and amplitude showed abrupt changes when crack initiated. When the crack initiation occurred, the loading stress of the specimens showed a notable retreat in the stress-strain curve, and the recorded AE energy and amplitude showed a sharp spike. These findings from this experimental study have been applied to the underground longwall mining to explain the failure mechanisms in the floor of the mining panel. The fracturing process associated with the pre-existing edge crack resembles the formation of flow channels for water inrush during longwall mining.

Study on Energy Accumulation and Damage Evolution of the Coal and Rock Using Acoustic Emission Test

2011 ◽  
Vol 105-107 ◽  
pp. 1597-1602 ◽  
Author(s):  
You Gang Wang ◽  
Xiang Feng Liu
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Solid Material ◽  
Damage Variable ◽  
Geometrical Parameters ◽  
Compression Process ◽  
Energy Accumulation ◽  
Ae Energy

Rocks and other rocklike solid materials have inherent defects inside. The defects of rock will be evolved under loading. The evolution process and extent of defects can be described by the damage variable. But which physical or geometrical parameters can be used to define the damage, there has no consistent conclusion domestic and aboard. Moreover, limited by the method of experimental, it is difficult to obtain the parameters to depict the damage variable directly. In order to obtained the evolution law of the interior defects in the solid material, the non-conduct geophysical prospecting measure as AE (Acoustic Emission) will be the leading measure to prospect the interior defects and it’s evolution under outside loading. In the present paper, the AE method was used to obtain the AE parameters during the uniaxial compression process of coal and rock. Therefore, uniaxial compression and AE tests on coal and mudstone were conducted, and the curves among the AE energy accumulation, stress and strain were obtained after analyzing the results of tests data. Based on the principle of damage mechanics and thermodynamics, the damage evolution of coal and rock was deduced through analyzing the experimental results, the curves of damage and AE accumulation were obtained also. By analyzing and fitting the curves of damage and AE energy accumulation, the relation between the AE energy accumulation and stress-strain was obtained and verified through the experimental data.

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