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 Experimental Research on Brittleness and Rockburst Proneness of Three Kinds of Hard Rocks under Uniaxial Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Rongchao Xu ◽  
Yiding Jin ◽  
Yumin Zhang
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Fracture Mechanism ◽  
Large Scale ◽  
Rock Fracture ◽  
Failure Process ◽  
High Energy ◽  
Brittle Rock ◽  
Evaluation Index ◽  
Unstable Crack

Rockburst is a highly destructive geological disaster caused by excavation and unloading of hard and brittle rock mass under high geostress environment. Quantitative evaluation of rock brittleness and rockburst proneness is one of the important tasks in potential rockburst assessment. In this study, uniaxial compression and acoustic emission tests were carried out for basalt, granite, and marble, and their brittleness and rockburst proneness were quantitatively evaluated. The acoustic emission evolution characteristics of the three rocks during uniaxial compression were analyzed, and the differences of fracture mechanism of the three rocks were compared. The results show that (1) based on the brittleness evaluation index, basalt is the most brittle rock, followed by granite, and marble is the weakest; (2) based on the rockburst proneness evaluation index, combined with the macroscopic failure phenomenon and morphology of the samples, the rockburst proneness of basalt is the strongest, followed by granite, and marble is the weakest; (3) there exists a positive correlation between rockburst proneness and brittleness, and the fitting results show that they are approximately exponential; and (4) brittleness has an important influence on the rock fracture mechanism. Unlike marble, basalt and granite with strong brittleness continuously present high-energy acoustic emission signals in the stage of unstable crack propagation, and large-scale fracture events continue to occur; from the calculation results of the acoustic emission b value, the stronger the brittleness of rock, the larger the proportion of large-scale fracture events in the failure process.

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.

Elasto-Plastic Cellular Automaton Simulation of Fracturing Process in Single Pre-Fractured Rocks under Uniaxial Compression

2010 ◽  
Vol 34-35 ◽  
pp. 383-386 ◽  
Author(s):  
Hua Yan Yao ◽  
Peng Zhi Pan
Keyword(s):  
Cellular Automaton ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Fractured Rock ◽  
Failure Process ◽  
Great Influence ◽  
Rock Fracturing ◽  
Rock Heterogeneity ◽  
Fracturing Process ◽  
Rock Specimens

Rock is a natural heterogeneous material and presents complicated behaviors in the fracturing process. It is prevail to study the basic failure mechanism of rocks via numerical simulation. Based on the elasto-plastic cellular automaton (EPCA) model, this paper simulates single pre-fractured rock fracturing process with consideration of rock heterogeneity on the meso-scale. In this model, the Weibull’s distribution, which characterizes heterogeneity with the homogeneous index m and the random seed parameter s, is adopted to describe the distribution of mechanical parameters of rock specimens such as cohesive strength, Young’s modulus, etc. Pre-existing crack rock specimens with different homogeneous index or the different random seed are simulated by EPCA under uniaxial compression. Numerical results show that heterogeneity has great influence on pre-fractured rock failure process, final failure modes, and the uniaxial compressive strength.

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 Quantitative Damage and Fracture Mode of Sandstone under Uniaxial Load Based on Acoustic Emission

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Ying Xu ◽  
Qiangqiang Zheng ◽  
Xin Gao ◽  
Rongzhou Yang ◽  
Xian Ni ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fracture Mechanism ◽  
Damage Mechanics ◽  
Shear Failure ◽  
Rock Fracture ◽  
Damage Model ◽  
Damage Models ◽  
Uniaxial Load ◽  
Damage And Fracture ◽  
Ae Signals

The damage degree and fracture mechanism of the rock are important to the bearing performance of the rock mass and the stability of the overlying structure. Most of the existing damage models for characterizing rock damage exclude the range of postpeak stress or do not consider the compaction and closure stage of the fracture, and the description of the quantitative damage of sandstone is not accurate enough. In addition, the description of the rock fracture mechanism under load is not exact enough. Aiming at the problem of quantitative damage and fracture mechanism of the loaded rock, this paper adopts acoustic emission (AE) to monitor the loading process of sandstone under uniaxial loading. In accordance with the characteristics of the AE signal, the loading stage of sandstone under uniaxial load is divided into three stages: initial hit stage, hit stability stage, and hit instability stage. By modifying the traditional damage model and combining the AE signals of the sandstone under the load, a modified damage mechanics model is obtained, which can fully express the entire loading stage. Furthermore, through the analysis of AE signals, the fracture mechanism of sandstone under uniaxial load is studied. The results show that the modified damage model can quantitatively describe the damage at different loading stages which include two areas including the fracture compaction closure stage and the postpeak stress stage. The failure and instability of sandstone under uniaxial load is mainly shear failure. The research results can provide a reference for the nondestructive testing of sandstone and engineering reliability in geotechnical engineering.

scholarly journals Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
X. L. Xu ◽  
Z.-Z. Zhang
Keyword(s):  
Acoustic Emission ◽  
High Temperatures ◽  
Count Rate ◽  
Shear Failure ◽  
Rock Fracture ◽  
Mechanical Damage ◽  
Strain Curve ◽  
Effect Of Temperature ◽  
Compression Tests ◽  
Ae Signals

Acoustic emission (AE) signals can be detected from rocks under the effect of temperature and loading, which can be used to reflect rock damage evolution process and predict rock fracture. In this paper, uniaxial compression tests of granite at high temperatures from 25°C to 1000°C were carried out, and AE signals were monitored simultaneously. The results indicated that AE ring count rate shows the law of “interval burst” and “relatively calm,” which can be explained from the energy point of view. From 25°C to 1000°C, the rock failure mode changes from single splitting failure to multisplitting failure, and then to incomplete shear failure, ideal shear failure, and double shear failure, until complete integral failure. Thermal damage (DT) defined by the elastic modulus shows logistic increase with the rise of temperature. Mechanical damage (DM) derived by the AE ring count rate can be divided into initial stage, stable stage, accelerated stage, and destructive stage. Total damage (D) increases with the rise of strain, which is corresponding to the stress-strain curve at various temperatures. Using AE data, we can further analyze the mechanism of deformation and fracture of rock, which helps to gather useful data for predicting rock stability at high temperatures.

Research on the AE Characteristic of the Rock with Rockburst Proneness

2014 ◽  
Vol 608-609 ◽  
pp. 689-692
Author(s):  
Mo Xiao Li ◽  
Guang Zhang ◽  
Jing Xi Chen
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Rock Mechanics ◽  
Compression Tests ◽  
Entire Process ◽  
The Relationship ◽  
Ae Signals

In this paper, in order to strengthen the prediction of rockburst and inquire the relationship between the rockburst proneness of rock and its AE characteristic, each kind of typical rock of volcanic, sedimentary and metamorphic were selected to doing indoor rock mechanics experiments. Calculate the rockburst proneness of these rocks by uniaxial compression tests. In uniaxial compression, we collect the entire process of AE signals by using acoustic emission instrument, then we analysis the AE characteristics of different rocks to inquire the relationship between the AE characteristic and its rockburst proneness.

Detection and Monitoring of Fatigue Cracks in Metallic Structures Using Acoustic Emission: Routes to Quantification of Probability of Detection

2014 ◽  
Vol 891-892 ◽  
pp. 1268-1274 ◽  
Author(s):  
Daniel Gagar ◽  
Peter Foote ◽  
Phil E. Irving
Keyword(s):  
Acoustic Emission ◽  
Fatigue Crack ◽  
Fatigue Cracks ◽  
Failure Process ◽  
Probability Of Detection ◽  
Metallic Structures ◽  
Final Failure ◽  
Ae Signal ◽  
Non Destructive ◽  
Ae Signals

The performance and reliability of Structural Health Monitoring (SHM) techniques remain largely unquantified. This is in contrast to the probability of detection (POD) and sensitivity of manual non destructive inspection methods which are well characterised. In this study factors influencing the rates of emission of Acoustic Emission (AE) signals from propagating fatigue cracks were investigated. Fatigue crack growth experiments were performed in 2014 T6 aluminium sheet to observe the effects of changes in crack length, loading spectrum and sample geometry on rates of emission and the probability of detecting and locating the fatigue crack. Significant variation was found in the rates of AE signal generation during crack progression from initiation to final failure. AE signals at any point in the failure process were found to result from different failure mechanisms operating at particular stages in the failure process.

scholarly journals Analysis of the results of acoustic emission diagnostics of a structure during helicopter fatigue tests

Aviation ◽  
2018 ◽  
Vol 21 (2) ◽  
pp. 64-69 ◽  
Author(s):  
Aleksandrs URBAHS ◽  
Kristine CARJOVA ◽  
Jurijs FESCUKS
Keyword(s):  
Acoustic Emission ◽  
Measurement Data ◽  
Fatigue Tests ◽  
Parameter Analysis ◽  
Inspection Method ◽  
Characteristic Structure ◽  
Ae Signal ◽  
Diagnostic Measurement ◽  
Non Destructive ◽  
Ae Signals

The study is devoted to a perspective diagnostic method, which makes it possible to deal with diagnostic tasks – the acoustic non-destructive inspection method based on acoustic emission (AE) signal parameter analysis. The practical use of this method is related to the interpretation of diagnostic measurement data. The parameters of acoustic emission (AE) signals were measured during bench tests of the tail boom structure and fin, as well as the joint areas of the fin, tail boom, and fuselage of the helicopter (joint area No.1 and No.19, frames of the tail boom and fuselage respectively).The analysis of fatigue damage kinetics was carried out in several stages for groups of bolts and for characteristic structure loading intervals. Bolt fracture was predicted at least 26 to 44 flight hours before the actual collapse. Using the AE parameters, the micro crack origin intervals identified when the bolt bearing capacity after the occurrence of the damage reached 96%.

scholarly journals Study on the Acoustic Emission Characteristics of Different Rock Types and Its Fracture Mechanism in Brazilian Splitting Test

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Shengxiang ◽  
Xie Qin ◽  
Liu Xiling ◽  
Li Xibing ◽  
Luo Yu ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Rock Fracture ◽  
Peak Frequency ◽  
Test System ◽  
Mineral Particle ◽  
Splitting Test ◽  
Ae Signal ◽  
The Relationship ◽  
Ae Signals ◽  
Internal Fracture

In order to investigate the relationship between rock microfracture mechanism and acoustic emission (AE) signal characteristic parameters under split loads, the MTS322 servo-controlled rock mechanical test system was employed to carry out the Brazilian split tests on granite, marble, sandstone, and limestone, while FEI Quanta-200 scanning electron microscope system was employed to carry out the analysis of fracture morphology. The results indicate that different scales of mineral particle, mineral composition, and discontinuity have influence on the fracture characteristics of rock, as well as the b-value. The peak frequency distribution of the AE signal has obvious zonal features, and these distinct peak frequencies of four types of rock fall mostly in ranges of 0–100 kHz, 100–300 kHz, and above 300 kHz. Due to the different rock properties and mineral compositions, the proportions of peak frequencies in these intervals are also different among the four rocks, which are also acting on the b-value. In addition, for granite, the peak frequencies of AE signals are mostly distributed above 300 kHz for granite, marble, and limestone, which mainly derive from the internal fracture of k-feldspar minerals; for marble, the AE signals with peak frequency are mostly distributed in over 300 kHz, which mainly derive from the internal fracture of dolomite minerals and calcite minerals; AE signals for sandstone are mostly distributed in the range of 0–100 kHz, which mainly derive from the internal fracture of quartz minerals; for limestone, the AE signals with peak frequency are mostly distributed in over 300 kHz, which mainly derive from the internal fracture of granular-calcite minerals. The relationship between acoustic emission signal frequency of rock fracture and the fracture scale is constructed through experiments, which is of great help for in-depth understanding of the scaling relationship of rock fracture.

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