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Mechanical anisotropy associated with beddings in shale under Brazilian test conditions:Insights from acoustic emission statistics
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作者 Yongfa Zhang Yinlin Ji +2 位作者 Yu Zhao Qinglin Deng Chaolin Wang 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第11期4462-4479,共18页
A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests wer... A comprehensive understanding of shale’s bedding anisotropy is crucial for shale-related engineering activities,such as hydraulic fracturing,drilling and underground excavation.In this study,seven Brazilian tests were conducted on shale samples at different bedding orientations with respect to the loading direction(0°,45°and 90°)and the disc end face(0°,45°and 90°).An acoustic emission(AE)system was employed to capture the evolution of damage and the temporal-spatial distribution of microcracks under splitting-tensile stress.The results show that the Brazilian tensile strength decreases with increasing bedding inclination with respect to the disc end face,while it increases with the angle between bedding and loading directions.Increasing the bedding inclination with respect to the end face facilitates the reduction in b value and enhances the shale’s resistance to microcrack growth during the loading process.Misalignment between the bedding orientation and the end face suppresses the growth of mixed tensile-shear microcracks,while reducing the bedding angle relative to the loading direction is beneficial for creating mixed tensile-shear and tensile cracks.The observed microscopic failure characteristics are attributed to the competing effects of bedding activation and breakage of shale matrix at different bedding inclinations.The temporal-spatial distribution of microcracks,characterized by AE statistics including the correlation dimension and spatial correlation length,illustrates that the fractal evolution of microcracks is independent of bedding anisotropy,whereas the spatial distribution shows a stronger correlation.The evolution features of correlation dimension and spatial correlation length could be potentially used as precursors for shale splitting failure.These findings may be useful for predicting rock mass instability and analyzing the causes of catastrophic rupture. 展开更多
关键词 Bedding anisotropy Acoustic emission(AE) SHALE Brazilian test Rock failure mechanism Splitting-tensile cracks
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Robot driver for vehicle durability emission test on chassis dynamometer 被引量:9
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作者 陈晓冰 张为公 《Journal of Southeast University(English Edition)》 EI CAS 2005年第1期33-38,共6页
A method for a vehicle durability emission test using a robot driver insteadof human drivers on the chassis dynamometer is presented. The system architecture of vehicledurability emission test cell, the road load simu... A method for a vehicle durability emission test using a robot driver insteadof human drivers on the chassis dynamometer is presented. The system architecture of vehicledurability emission test cell, the road load simulation strategy and the tele-monitoring systembased on Browser/Client structure are described. Furthermore, the construction of the robot driver,vehicle performance self-learning algorithm, multi-mode vehicle control model and vehicle speedtracking strategy based on fuzzy logic arealso discussed. Besides, the capability of controlparameters self-compensation on-line makes it possible to compensate the wear of vehicle componentsand the variety of clutch true bite point during the long term test. Experimental results show thattherobot driver can be applicable to a wide variety of vehicles and the obtained results stay withina tolerance band of ± 2 km/h. Moreover the robot driver is able to control tested vehicles withgood repeatability and consistency; therefore, this methodpresents a solution to eliminate theuncertainty of emission test results by human drivers and to ensure the accuracy and reliability ofemission test results. 展开更多
关键词 robot driver durability emission test chassis dynamometer driving testcycle
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Microscopic damage evolution of anisotropic rocks under indirect tensile conditions: Insights from acoustic emission and digital image correlation techniques 被引量:2
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作者 Chaoqun Chu Shunchuan Wu +1 位作者 Chaojun Zhang Yongle Zhang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2023年第9期1680-1691,共12页
The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedd... The anisotropy induced by rock bedding structures is usually manifested in the mechanical behaviors and failure modes of rocks.Brazilian tests are conducted for seven groups of shale specimens featuring different bedding angles. Acoustic emission (AE) and digital image correlation (DIC) technologies are used to monitor the in-situ failure of the specimens. Furthermore, the crack morphology of damaged samples is observed through scanning electron microscopy (SEM). Results reveal the structural dependence on the tensile mechanical behavior of shales. The shale disk exhibits compression in the early stage of the experiment with varying locations and durations. The location of the compression area moves downward and gradually disappears when the bedding angle increases. The macroscopic failure is well characterized by AE event location results, and the dominant frequency distribution is related to the bedding angle. The b-value is found to be stress-dependent.The crack turning angle between layers and the number of cracks crossing the bedding both increase with the bedding angle, indicating competition between crack propagations. SEM results revealed that the failure modes of the samples can be classified into three types:tensile failure along beddings with shear failure of the matrix, ladder shear failure along beddings with tensile failure of the matrix, and shear failure along multiple beddings with tensile failure of the matrix. 展开更多
关键词 anisotropic rock failure mechanism acoustic emission digital image correlation Brazilian test
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Acoustic emission characterization of microcracking in laboratory-scale hydraulic fracturing tests 被引量:9
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作者 Jesse Hampton Marte Gutierrez +2 位作者 Luis Matzar Dandan Hu Luke Frash 《Journal of Rock Mechanics and Geotechnical Engineering》 CSCD 2018年第5期805-817,共13页
Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and ... Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces (i.e. damage). Acoustic emission (AE) monitoring and analysis provide unique information regarding the microcracking process temporally, and infor- mation concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of under- standing the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. It was quantitatively observed that the recorded AE signals provided sufficient information to generalize the damage radiating spatially away from the injection wellbore. 展开更多
关键词 Acoustic emission (AE) Microcracking Hydraulic fracturing Laboratory-scale testing Moment tensor analysis Fracture coalescence Computed tomography (CT) imaging
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Acoustic emission activity in directly tensile test on marble specimens and its tensile damage constitutive model 被引量:12
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作者 Ruifu Yuan Bowen Shi 《International Journal of Coal Science & Technology》 EI 2018年第3期295-304,共10页
For understanding acoustic emission (AE) activity and accumulation of micro-damage inside rock under pure tensile state, the AE signals has been monitored on the test of directly tension on two kinds of marble speci... For understanding acoustic emission (AE) activity and accumulation of micro-damage inside rock under pure tensile state, the AE signals has been monitored on the test of directly tension on two kinds of marble specimens. A tensile constitutive model was proposed with the damage factor calculated by AE energy rate. The tensile strength of marble was discrete obviously and was sensitive to the inside microdefects and grain composition. With increasing of loading, the tensile stress-strain curve obviously showed nonlinear with the tensile tangent modulus decreasing. In repeated loading cycle, the tensile elastic modulus was less than that in the previous loading cycle because of the generation of micro damage during the prior loading. It means the linear weakening occurring in the specimens. The AE activity was corresponding with occurrence of nonlinear deformation. In the initial loading stage which only elastic deformation happened on the specimens, there were few AE events occurred; while when the nonlinear deformation happened with increasing of loading, lots of AE events were generated. The quantity and energy of AE events were proportionally related to the variation of tensile tangent modulus. The Kaiser effect of AE activity could be clearly observed in tensile cycle loading. Based on the theory of damage mechanics, the damage factor was defined by AE energy rate and the tensile damage constitutive model was proposed which only needed two property constants. The theoretical stress-strain curve was well fitted with the curve plotted with tested datum and the two property constants were easily gotten by the laboratory testing. 展开更多
关键词 Marble specimens Direct tensile test Acoustic emission Tensile tangent modulus Damage constitutive model
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Uniaxial compression CT and acoustic emission test on the coal crack propagation destruction process 被引量:1
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作者 Jing-hong LIU Yao-dong JIANG +1 位作者 Yi-xin ZHAO Jie ZHU 《Journal of Coal Science & Engineering(China)》 2013年第1期69-74,共6页
Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test compa... Acoustic emission test and CT scanning are important techniques in the study of coal crack propagation. A uniaxial compression test was performed on coal samples by integrating CT and acoustic emission. The test comparison analyzes the acoustic emission load and CT images for an effective observation on the entire process, from crack propagation to the samples' destruction. The box dimension of the coal samples' acoustic emission series and the CT images were obtained through calculations by using the authors' own program. The results show that the fractal dimension of both the acoustic emission energy and CT image increase rapidly, indicating coal and rock mass has entered a dangerous condition. Hence, measures should be taken to unload the pressure of the coal and rock mass. The test results provide intuitive observation data for the coal meso-damage model. The test contributes to in-depth studies of coal or rock crack propagation mechanisms and provides a theoretical basis for rock burst mechanism. 展开更多
关键词 acoustic emission test CT test fractal dimension destruction process
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Interface fracture toughness and fracture mechanisms of thermal barrier coatings investigated by indentation test and acoustic emission technique 被引量:1
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作者 Han Jiceng Guo Ping +2 位作者 Luo Jianxia Zhang Zhichao Li Qiang 《China Welding》 EI CAS 2016年第3期63-70,共8页
Interface fracture toughness and fracture mechanisms of plasma-/sprayed thermal barrier coatings (TBCs) were investigated by interfacial indentation test ( HT) in combination with acoustic emission ( AE ) measur... Interface fracture toughness and fracture mechanisms of plasma-/sprayed thermal barrier coatings (TBCs) were investigated by interfacial indentation test ( HT) in combination with acoustic emission ( AE ) measurement. Critical load and AE energy were employed to calculate interface fracture toughness. The critical point at which crack appears at the interface was determined by the HT. AE signals produced during total indentation test not only are used to investigate the interface cracking behavior by Fast Fourier Transform (FFT) and wavelet transforms but also supply the mechanical information. The result shows that the AE signals associated with coating plastic deformation during indentation are of a more continuous type with a lower characteristic frequency content (30 -60 kHz) , whereas the instantaneous relaxation associated with interface crack initiation produces burst type AE signals with a characteristic frequency in the range 70 - 200 kHz. The AE signals energy is concentrated on different scales for the coating plastic deformation, interface crack initiation and interface crack propagation. Interface fracture toughness calculated by AE energy was 1. 19 MPam1/2 close to 1.58 MPam1/2 calculated by critical load. It indicates that the acoustic emission energy is suitable to reflect the interface fracture toughness. 展开更多
关键词 thermal barrier coating acoustic emission interface indentation test interface fracture toughness
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Application of acoustic emission (AE) technique in crack monitor during fatigue test of pump rods 被引量:3
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作者 XIA Yong-fa LI Hai-ling 《材料与冶金学报》 CAS 2007年第1期60-63,共4页
关键词 水泵杆 机械疲劳 声音散射法 裂缝 监测
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Electrical Emissions from Concrete under Three-point Bending Tests
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作者 刘清平 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2005年第2期102-104,共3页
Electrical emission (EM) signals, which are generated from the concrete specimens under three-point bending tests, were conducted. It is shown that electrical emission phenomena are related to cracking of the specimen... Electrical emission (EM) signals, which are generated from the concrete specimens under three-point bending tests, were conducted. It is shown that electrical emission phenomena are related to cracking of the specimens, cohesive failure, contact-separation etc. The simultaneous appearance of electric emission signals and visible cracks during the flexure loading of beams was also observed. 展开更多
关键词 cement and concrete electrical emission non-destruction test
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Ion Photon Emission Microscope for Single Event Effect Testing in CIAE
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作者 张艳文 郭刚 +4 位作者 刘建成 史淑廷 覃英参 李丽丽 贺林峰 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第7期71-75,共5页
Ion photon emission microscopy (IPEM) is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an... Ion photon emission microscopy (IPEM) is a new ion-induced emission microscopy. It employs a broad ion beam with high energy and low fluence rate impinging on a sample. The position of a single ion is detected by an optical system with objective lens, prism, microscope tube and charge coupled device (CCD). A thin ZnS film doped with Ag ions is used as a luminescent material. Generation efficiency and transmission efficiency of photons in the ZnS(Ag) film created by irradiated Cl ions are calculated. A single Cl ion optical microscopic image is observed by high quantum efficiency CCD. The resolution of a single Cl ion given in this IPEM system is 6μm. Several factors influencing the resolution are discussed. A silicon diode is used to collect the electrical signals caused by the incident ions. Effective and accidental coincidence of optical images and electronic signals are illustrated. A two-dimensional map of single event effect is drawn out according to the data of effective coincidence. 展开更多
关键词 AG ZNS Ion Photon emission Microscope for Single Event Effect testing in CIAE
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Acoustic Emission Properties of Concrete Slab During Fatigue Testing with a Running-Wheel Load
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作者 Mitsuharu Shiwa Zhengwang Li +2 位作者 Takuya Maeshima Yasuhiro Koda Yasushi Tanaka 《Journal of Civil Engineering and Architecture》 2017年第3期213-221,共9页
AE (acoustic emission) signals from concrete slab during fatigue testing with a running-wheel load were evaluated. The signals were recorded by remote sensors connected to a computer network. The sensing equipment c... AE (acoustic emission) signals from concrete slab during fatigue testing with a running-wheel load were evaluated. The signals were recorded by remote sensors connected to a computer network. The sensing equipment consisted of 60 kHz resonant-type AE sensors mounted on a reinforcing steel bar as a waveguide, together with a 16-channel sensor highway AE system. Because the detected AE signals included periodic mechanical noise from the motion of the wheel, these noises were eliminated by means of signal processing. The AE waveguide measurement over a length of 3 m detected fractures as vertical and horizontal cracks in the RC (reinforced concrete) slab. Those cracks were analyzed by correlating AE parameters with macroscopic distortions and the numbers of fatigue cycles. In the AE events and AE energy, two types of AE phenomena, active region and inactive region, were observed during fatigue testing. The vertical cracks were characterized by an AE amplitude of 58 dB, a peak frequency of 30 kHz, and a ratio of the rise time to the maximum amplitude value (RA) of 100. The horizontal cracks were characterized by an AE amplitude of 85 dB, a peak frequency of 60 kHz, and an RA value of 10. 展开更多
关键词 Acoustic emission concrete slab WAVEGUIDE fatigue testing running-wheel load.
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On the Bump Tests of Cracked Shafts Using Acoustic Emission Techniques
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作者 Gilberto Luiz S. Pimentel-Junior Frederico B. Oliveira Marco Tulio C. Faria 《Engineering(科研)》 2016年第9期572-581,共11页
An investigation about the application of Acoustic Emission (AE) techniques to analyze the dynamic response of different cracked shafts rendered in bump tests is presented in this work. The experimental apparatus devi... An investigation about the application of Acoustic Emission (AE) techniques to analyze the dynamic response of different cracked shafts rendered in bump tests is presented in this work. The experimental apparatus devised for this work complies of six shafts with different transverse crack sizes and a high-frequency data acquisition system. The AE signals generated in the bump tests performed on the different cracked shafts are captured by a wideband AE transducer. Those signals are treated by using statistical moments, wavelet transforms, and frequency- and time-domain procedures. A transverse crack of predetermined depth is etched into each shaft. The experimental results show that the values of kurtosis and skewness estimated for the AE signals can be used to identify the crack size. 展开更多
关键词 Acoustic emission Cracked Rotors Bump tests Shaft Crack
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INVESTIGATION IN REDUCING EXHAUST EMISSIONS FROM TWO STROKE MOTORCYCLES 被引量:1
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作者 王颂秦 白景升 林漫群 《Transactions of Tianjin University》 EI CAS 1998年第1期3-8,共6页
Test results of reducing two stroke motorcycle emissions with new type carburettors and electronic fuel injection systems are presented. Analyses and comparison between different systems are discussed. The adoption o... Test results of reducing two stroke motorcycle emissions with new type carburettors and electronic fuel injection systems are presented. Analyses and comparison between different systems are discussed. The adoption of electronically controlled injection and corresponding electronic control technique is an effective measure of prolonged vitality to improve emissions from two stroke motorcycles. Suggestions about the strategic steps of China′s motorcycle emission control are proposed. 展开更多
关键词 two stroke motorcycle engine carburettor electronic control injection system controlled stratified combustion emission test for exhaust emission from motorcycle
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GRA BASED ANALYSIS ON FACTORS INFLUENCING CO_2 EMISSIONS IN CHINA 被引量:1
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作者 董锋 李晓晖 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2012年第2期152-158,共7页
How to achieve the objective of reducing CO2 emissions has been an academic focus in China recently. The factors influencing CO2 emissions are the vital issue to accomplish the arduous target. Firstly, three influenti... How to achieve the objective of reducing CO2 emissions has been an academic focus in China recently. The factors influencing CO2 emissions are the vital issue to accomplish the arduous target. Firstly, three influential factors, the energy consumption, the proportion of tertiary industry in gross domestic product (GDP), and the degree of dependence on foreign trade, are carefully selected, since all of them have closer grey relation with China's COz emissions compared with others when the grey relational analysis (GRA) method is applied. The study highlights co-integration relation of these four variables using the co-integration analysis method. And then a long-term co-integration equation and a short-term error correction model of China's CO2 emissions are devel- oped. Finally, the comparison is exerted between the forecast value and the actual value of China's CO2 emissions based on error correction model. The results and the relevant statistics tests show that the pro- posed model has better explanation capability and credibility. 展开更多
关键词 grey relational analysis(GRA) CO2 emissions co-integration test error correction model
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Identification of damage mode in AZ31 magnesium alloy under tension using acoustic emission 被引量:1
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作者 常红 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2015年第6期1840-1846,共7页
In order to characterize different damage modes, real-time detection of the tensile cracking process for AZ31 magnesium alloy was performed using acoustic emission (AE) technique. Results showed that elastic deforma... In order to characterize different damage modes, real-time detection of the tensile cracking process for AZ31 magnesium alloy was performed using acoustic emission (AE) technique. Results showed that elastic deformation, plastic deformation, microcracking, stable and unstable propagation occurred during crack damage. Four damage modes were determined using AE multiparameter analysis. Dislocation motion signals with amplitudes 〈70 dB and twinning signals with 70-100 dB were found. Microcrack signal energy was concentrated from 2400 aJ to 4100 aJ, mainly at a rise time of less than 800 gs. A stable crack propagation signal had high peak to counts in the 20 to 50 range, whereas its ring count was in the 20 to 2000 range. The average frequency of unstable propagation signals was approximately 100 kHz, with duration from 2000 gs to 10s gs. The damage mechanisms and AE resources from different crack propagation steps were discussed. Various damage modes could be characterized by different AE signal parameters when they appeared simultaneously during crack propagation. 展开更多
关键词 acoustic emission multi-parameter analysis damage characterization tension testing magnesium alloy
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Space-time evolution rules of acoustic emission location of unloaded coal sample at different loading rates 被引量:9
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作者 Ai Ting Zhang Ru +1 位作者 Liu Jianfeng Ren Li 《International Journal of Mining Science and Technology》 SCIE EI 2012年第6期847-854,共8页
By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities ... By using MTS815 rock mechanics test system,a series of acoustic emission(AE) location experiments were performed under unloading confining pressure,increasing the axial stress.The AE space-time evolution regularities and energy releasing characteristics during deformation and failure process of coal of different loading rates are compared,the influence mechanism of loading rates on the microscopic crack evolution were studied,combining the AE characteristics and the macroscopic failure modes of the specimens,and the precursory characteristics of coal failure were also analyzed quantitatively.The results indicate that as the loading rate is higher,the AE activity and the main fracture will begin earlier.The destruction of coal body is mainly the function of shear strain at lower loading rate and tension strain at higher rate,and will transform from brittleness to ductility at critical velocities.When the deformation of the coal is mainly plasticity,the amplitude of the AE ringing counting rate increases largely and the AE energy curves appear an obvious ''step'',which can be defined as the first failure precursor point.Statics of AE information shows that the strongest AE activity begins when the axial stress level was 92-98%,which can be defined as the other failure precursor point.As the loading rate is smaller,the coal more easily reaches the latter precursor point after the first one,so attention should be aroused to prevent dynamic disaster in coal mining when the AE activity reaches the first precursor point. 展开更多
关键词 Acoustic emission testing Acoustic emissions COAL Coal mines DEFORMATION Disaster prevention Fracture mechanics Rock mechanics Shear strain Strain rate UNLOADING
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Real-world vehicle emission factors in Chinese metropolis city—Beijing 被引量:8
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作者 WANGQi-dong HEKe-bin +1 位作者 HUOHong JamesLents 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2005年第2期319-326,共8页
The dynamometer tests with different driving cycles and the real-world tests are presented. Results indicated the pollutants emission factors and fuel consumption factor with ECE15+EUDC driving cycle usually take the ... The dynamometer tests with different driving cycles and the real-world tests are presented. Results indicated the pollutants emission factors and fuel consumption factor with ECE15+EUDC driving cycle usually take the lowest value and with real world driving cycle occur the highest value, and different driving cycles will lead to significantly different vehicle emission factors with the same vehicle. Relative to the ECE15+EUDC driving cycle, the increasing rate of pollutant emission factors of CO, NOx and HC are -0.42—2.99, -0.32 —0.81 and -0.11—11 with FTP75 testing, 0.11—1.29, -0.77—0.64 and 0.47—10.50 with Beijing 1997 testing and 0.25—1.83, 0.09—0.75 and -0.58—1.50 with real world testing. Compared to the carburetor vehicles, the retrofit and MPI+TWC vehicles' pollution emission factors decrease with different degree. The retrofit vehicle(Santana) will reduce 4.44%—58.44% CO, -4.95%—36.79% NOx, -32.32%—33.89% HC, and -9.39%—14.29% fuel consumption, and especially that the MPI+TWC vehicle will decrease CO by 82.48%—91.76%, NOx by 44.87%—92.79%, HC by 90.00%—93.89% and fuel consumption by 5.44%—10.55%. Vehicles can cause pollution at a very high rate when operated in high power modes; however, they may not often operate in these high power modes. In analyzing vehicle emissions, it describes the fraction of time that vehicles operate in various power modes. In Beijing, vehicles spend 90% of their operation in low power modes or decelerating. 展开更多
关键词 real-world testing vehicle emission factors driving cycle power modes
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Uniaxial experimental study of the acoustic emission and deformation behavior of composite rock based on 3D digital image correlation(DIC) 被引量:17
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作者 Jian-Long Cheng Sheng-Qi Yang +3 位作者 Kui Chen Dan Ma Feng-Yuan Li Li-Ming Wang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2017年第6期999-1021,共23页
In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic ... In this paper, uniaxial compression tests were carried out on a series of composite rock specimens with different dip angles, which were made from two types of rock-like material with different strength. The acoustic emission technique was used to monitor the acoustic signal characteristics of composite rock specimens during the entire loading process. At the same time, an optical non-contact 3 D digital image correlation technique was used to study the evolution of axial strain field and the maximal strain field before and after the peak strength at different stress levels during the loading process. The effect of bedding plane inclination on the deformation and strength during uniaxial loading was analyzed. The methods of solving the elastic constants of hard and weak rock were described. The damage evolution process, deformation and failure mechanism, and failure mode during uniaxial loading were fully determined. The experimental results show that the θ = 0?–45?specimens had obvious plastic deformation during loading, and the brittleness of the θ = 60?–90?specimens gradually increased during the loading process. When the anisotropic angle θincreased from 0?to 90?, the peak strength, peak strain,and apparent elastic modulus all decreased initially and then increased. The failure mode of the composite rock specimen during uniaxial loading can be divided into three categories:tensile fracture across the discontinuities(θ = 0?–30?), slid-ing failure along the discontinuities(θ = 45?–75?), and tensile-split along the discontinuities(θ = 90?). The axial strain of the weak and hard rock layers in the composite rock specimen during the loading process was significantly different from that of the θ = 0?–45?specimens and was almost the same as that of the θ = 60?–90?specimens. As for the strain localization highlighted in the maximum principal strain field, the θ = 0?–30?specimens appeared in the rock matrix approximately parallel to the loading direction,while in the θ = 45?–90?specimens it appeared at the hard and weak rock layer interface. 展开更多
关键词 Uniaxial compression tests on composite rock ANISOTROPY Elastic constant Failure mode 3D digital image correlation Acoustic emission Strain field
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Acoustic emission precursors of static and dynamic instability for coarse-grained hard rock 被引量:13
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作者 SU Guo-shao GAN Wei +1 位作者 ZHAI Shao-bin ZHAO Guo-fu 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第10期2883-2898,共16页
To investigate the acoustic emission(AE)precursors of coarse-grained hard rock instability,an experimental study on the rockburst and slabbing process of granite was carried out using a true triaxial test system.The e... To investigate the acoustic emission(AE)precursors of coarse-grained hard rock instability,an experimental study on the rockburst and slabbing process of granite was carried out using a true triaxial test system.The evolution of the AE signals was monitored and analyzed in terms of the AE hit rate,fractal dimension of the AE hit number,AE count rate,b-value,dominant frequency and microcrack type.The test results show that after rock slabbing occurs,the AE precursors that can be used to predict the final dynamic instability(rockburst)are as follows:indicators such as the AE hit rate and AE count rate suddenly increase and then suddenly decrease;the AE hit rate exhibits a“quiet period”;during the“quiet period”,a small number of high-amplitude and low-frequency hits occur,and the signals corresponding to shear fracture continue to increase.The AE precursors for the final static instability(spalling)are as follows:both the AE hit rate and the b-value continuously decrease,and intermittent sudden increases appear in the high-frequency hits or the AE count rate. 展开更多
关键词 ROCKBURST slabbing SPALLING acoustic emission true triaxial test
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Study of electromagnetic and acoustic emission in creep experiments of water-containing rock samples 被引量:7
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作者 JING Hong-wen ZHANG Zhong-yu XU Guo-an 《Journal of China University of Mining and Technology》 EI 2008年第1期42-45,共4页
Based on biaxial shear creep tests conducted on rock samples with different water contents, we present the results of our study on the regularities of electromagnetic and acoustic emission during the process of creep ... Based on biaxial shear creep tests conducted on rock samples with different water contents, we present the results of our study on the regularities of electromagnetic and acoustic emission during the process of creep experiments in which we have analyzed the contribution of water to the occurrence of electromagnetic radiation. The result shows that in the creep-fracturing course of rock samples, when the water content increases, the initial frequency and amplitude of electromagnetic and acoustic emission also increases, but at a decreasing growth rate caused by loading stress. This can be used as a criterion for the long-term stability of rock masses under conditions of repeated inundation and discharge of water. 展开更多
关键词 electromagnetic emission (EME) acoustic emission (AE) biaxial shear creep tests water content
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