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 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 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.

Behavior and Fracture Mechanism of Brittle Rock with Pre-Existing Parallel Cracks

2006 ◽  
Vol 324-325 ◽  
pp. 1055-1058 ◽  
Author(s):  
M.X. Zhang ◽  
X.L. Lee ◽  
A.A. Javadi
Keyword(s):  
Fracture Mechanism ◽  
Rock Fracture ◽  
Strength Criterion ◽  
Brittle Rock ◽  
Fracture Mechanisms ◽  
Stress Equilibrium ◽  
Parallel Cracks ◽  
Micro Cracks ◽  
Griffith Theory ◽  
Almost All

There is a macro-crack and micro-crack system in rock, which affects almost all the mechanical properties of rock, especially for the fracture mechanism. The propagation of pre-existing cracks in rock samples under load is fundamental to understanding of rock fracture mechanisms. It is evident that assumption of Griffith theory was not in accord with the fact that numerous cracks exist in rock. So, it is difficult to explain how the propagation of a micro-crack developed into macro-failure by conventional theories. In order to investigate the cause and results of fracture within the rock, the stress concentration around the micro-cracks was analyzed, which resulted in propagation of wing cracks and connecting adjacent original cracks, eventually leading to macro-failure. The experiments on gypseous samples with pre-existing parallel cracks (flat rectangular in shape) under compression were carried out. The fracture mechanism and the stress equilibrium condition at brittle rock were discussed. Based on the fracture mechanism of brittle rock, a strength criterion of rock was proposed.

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 Rock Stability Assessment Based on the Chronological Order of the Characteristic Acoustic Emission Phenomena

2018 ◽  
Vol 2018 ◽  
pp. 1-10
Author(s):  
Penghai Zhang ◽  
Tianhong Yang ◽  
Tao Xu ◽  
Qinglei Yu ◽  
Jingren Zhou ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Failure Process ◽  
High Energy ◽  
Development Stage ◽  
Crack Development ◽  
Stability Assessment ◽  
Chronological Order ◽  
Granitic Gneiss ◽  
High Energy Level ◽  
Rock Stability

Sudden inelastic deformations in rock are associated with acoustic emission (AE). Therefore, AE monitoring technique can be used to study the fracture processes of rock. In this paper, AE tests were conducted on the granitic gneiss specimens under the uniaxial compressive loading conditions. The temporal changes in AE hit parameters and spatial-temporal evolution of AE events during the failure process of the granitic gneiss specimens were studied, and several characteristic AE phenomena (i.e., dramatic increase in dominant frequency, AE energy, and hit rate, the AE event with a high energy level, and the through-going distribution of the AE events with intermediate energy levels) were statistically analyzed before the failure occurred. It was found that the chronological order of the characteristic AE phenomena was relatively certain and correspondingly had a close relationship with the crack development stage. Because of the difference of the stress level at each crack development stage, the stability at different crack development stages is different. Therefore, a rock stability assessment approach was established based on the chronological order of the characteristic AE phenomena, and then the rock stability was assessed using the proposed approach.

Heat Induced Fracturing of Rock in an Existing Uniaxial Stress Field

1985 ◽  
Vol 50 ◽  
Author(s):  
J. I. Mathis ◽  
O. Stehpansson ◽  
B. Bjarnason ◽  
H. Hakami ◽  
A. Herdocia ◽  
...  
Keyword(s):  
Large Scale ◽  
Failure Time ◽  
Rock Fracture ◽  
Failure Process ◽  
Uniaxial Stress ◽  
Time To Failure ◽  
Rock Breakage ◽  
Rock Fracturing ◽  
Thermal Failure ◽  
Thermal Fracturing

AbstractThe thermal fracturing of rock has been the object of several research projects, notably for initial rock breakage in mining [4] as well as crushing [6] In addition, the process has been studied carefully in regards to the storage of radioactive waste underground where rock fracturing could lead to a loss of radioactivity confinement. The Stripa Project, a project concerning large scale testing of procedures for underground storage of nuclear waste, probably has dealt most thoroughly with this subject by theoretical studies and in-situ heater testing in an attempt to describe the thermal failure process in rock [13]This project was designed to test the agreement between theoretical and actual rock fracture times of a rock block, loaded with a physical as well as a thermal load. Laboratory testing consisted of physically loading center-drilled cubes of rock, 0.3 m on a side, uniaxially from 0 to 25 MPa. These were then thermally loaded with a nominal 3.7 kW (factory rating) cylindrical heater until failure occurred. This time to failure was recorded for comparison with a direct mathematical and a finite element solution. For both cases, calculations were performed at specific time-steps and an estimated failure time calculated from the compiled results.

Uniaxial Compression with Acoustic Emission Experimental Study on Rock Damage Process

2012 ◽  
Vol 204-208 ◽  
pp. 173-176
Author(s):  
Jing Hong Liu ◽  
Xiao Hua Liu ◽  
Wen Han
Keyword(s):  
Acoustic Emission ◽  
Crack Propagation ◽  
Uniaxial Compression ◽  
Failure Process ◽  
Structure Stability ◽  
Uniaxial Compression Test ◽  
Concrete Material ◽  
Deformation And Failure ◽  
Disaster Assessment ◽  
Contrast Analysis

Acoustic emission technique is an important technique for monitoring crack propagation and failure process of rock, coal and concrete material. A uniaxial compression test with acoustic emission monitoring on coal and rock samples’ deformation and failure process were carried out. Failure precursor information of rock, coal and concrete material were studied through contrast analysis the experiment result include acoustic emission signals, strain, load correlation of sample inner crack propagation to failure process. The test provided necessary data to further understand on rock burst failure disaster. The test result provides a theoretical basis for further application of acoustic emission for prediction coal rock dynamic disaster, assessment rock and concrete structure stability and study rock concrete material failure process mechanism.

Numerical Study of Effect of Joint Tip Distance from Sample End on Rock Failure

2014 ◽  
Vol 501-504 ◽  
pp. 244-247
Author(s):  
Yun Jie Zhang ◽  
Cheng Fan
Keyword(s):  
Uniaxial Compression ◽  
Numerical Study ◽  
Process Analysis ◽  
Rock Fracture ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Rock Failure ◽  
Peak Strain ◽  
Failure Patterns

In this paper,the mechanical properties of rock experiencing the variation of joint tip distance from sample end under uniaxial compression condition were simulated.Numerical simulation for the different rock sample in the uniaxial compression have been conducted to evaluate the effects of joint tip distance from sample end on the overall mechanical behaviour of jointed rock masses. It was done using the Rock Failure Process Analysis program RFPA2D. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding physical tests. We found that specimen joint tip distance from sample end corresponding value (distance from the crack tip to the compression surface) linear relationship with the compressive strength values .Numerical simulations agree well with physical results, it is shown that RFPA2D is suitable for the analysis of joint tip distance from sample end effect on rock fracture.

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