Fracture damage prediction in fissured red sandstone under uniaxial compression: acoustic emission b ‐value analysis

2019 ◽  
Vol 43 (1) ◽  
pp. 175-190 ◽  
Author(s):  
Yong Niu ◽  
Xiao‐Ping Zhou ◽  
Lun‐Shi Zhou
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
B Value ◽  
Value Analysis ◽  
Damage Prediction ◽  
Red Sandstone ◽  
Fracture Damage

scholarly journals Cracking Behavior and Acoustic Emission Characteristics of Rock Containing a Single Preexisting Flaw

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xunjian Hu ◽  
Lina Luo ◽  
Gang Lei ◽  
Xiaonan Gong ◽  
Panpan Guo ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
B Value ◽  
Strength Properties ◽  
Force Chain ◽  
Particle Flow Code ◽  
Mechanical Heterogeneity ◽  
Cracking Behavior ◽  
Brittle Rocks ◽  
Prone Area

The existence of flaws in brittle rocks or rock-like materials has an obvious influence on the material mechanical properties and cracking behavior of civil engineering projects. In this work, the two-dimensional particle flow code PFC2D was used to study the deformation and strength properties, failure processes, and acoustic emission (AE) characteristics of mudstone with a single preexisting flaw. First, the procedure to construct a parallel bond model is introduced. The Weibull distribution is used to reflect the mechanical heterogeneity of rocks. Then, the microscopic parameters used in PFC2D are calibrated to the macroproperties of mudstone obtained from laboratory tests under the uniaxial compression. The results indicate that the increases of the flaw inclination lead to the increasing uniaxial compressive strength and elastic modulus. In terms of microcrack evolution, the initiation, propagation, and coalescence of microcracks are closely related to the force chain. Specifically, an “X” shaped tension force chain concentrated area around the preexisting flaw is founded, which is the most prone area for microcracks to initiate. With an increase in flaw inclination, the b value of AE also shows an increasing trend. By incorporating the AE event numbers into a damage variable, this paper derives a constitutive model, which is verified by numerical results on brittle rocks with a single preexisting flaw under uniaxial compression.

scholarly journals Experimental Study on Source Failure Mechanism and Acoustic Emission Characteristics of Red Sandstone Under Uniaxial Compression

2021 ◽  
Author(s):  
Hailiang Xu ◽  
Wanyu Zhu ◽  
Yimin Song ◽  
Dong An ◽  
Hehuan Ren
Keyword(s):  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Sudden Change ◽  
Rock Deformation ◽  
Deformation Localization ◽  
Main Frequency ◽  
Red Sandstone ◽  
Localization Zone ◽  
Spectrum Distribution ◽  
Frequency Components

Abstract In order to study the rock fracture mechanism and precursor characteristics, uniaxial compression experiments of red sandstone were carried out. Using acoustic emission technology and digital speckle correlation method as experimental observation means, the evolution characteristics of deformation field and acoustic emission index during rock deformation were studied. The results show that : (1) The deformation concentration of rock deformation localization zone is the main cause of nonlinear evolution of rock stress-strain curve. (2) The volume parameters of different types of cracks in rock acoustic emission change with the relative displacement rate and dislocation rate of deformation localization zone. (3) In terms of failure types, there are more high-frequency components of tensile fracture main frequency, more low-frequency components of shear fracture main frequency, and wider distribution of mixed fracture main frequency. In the time sequence, the spectrum distribution of acoustic emission signals is wide and the amplitude is small at the sudden change time. At the sudden change time, the spectrum distribution of acoustic emission signals becomes narrow, the amplitude increases, and the spectrum distribution of peak points is greatly narrowed. Therefore, it is considered that the spectrum distribution is greatly narrowed can be used as an early warning precursor.

B-Value Analysis of AE Signal Subjected to Stepwise Loading

2011 ◽  
Vol 403-408 ◽  
pp. 4126-4131 ◽  
Author(s):  
Noorsuhada Md Nor ◽  
Norazura Muhamad Bunnori ◽  
Ibrahim Azmi ◽  
Shahidan Shahiron ◽  
Siti Ramziah Basri ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
B Value ◽  
Assessment Method ◽  
Value Analysis ◽  
Magnitude Distribution ◽  
Ae Signal ◽  
Linear Slope ◽  
Log Linear ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude

Acoustic emission is an effective damage assessment method in a structure subjected to mechanical loading. Calculation of log-linear slope of the frequency-magnitude distribution of acoustic emission (known as b-value) has been carried out. It is found that the b-valuefor the log frequency-magnitude graph has a good correlation for beam imposed of stepwise loading.It also can be seen that the b-value is decreased as the load increased.

scholarly journals Acoustic Emission Characteristics and Energy Evolution of Red Sandstone Samples under Cyclic Loading and Unloading

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Tianzuo Wang ◽  
Chunli Wang ◽  
Fei Xue ◽  
Linxiang Wang ◽  
Beyene Hana Teshome ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Dissipated Energy ◽  
Strengthening Effect ◽  
Energy Rate ◽  
Red Sandstone ◽  
Rock Samples ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

To explore the characteristics of rock deformation and failure under cyclic loading and unloading, the MTS815 rock mechanics test system and acoustic emission (AE) signal acquisition system were used to perform cyclic loading and unloading tests on red sandstone samples. The results showed that, compared with the uniaxial compression test, cyclic loading and unloading had a certain strengthening effect on the strength of the samples. The plastic deformation of the rock samples increased as the number of cycles increased. Based on AE signals, the cracking mode classification was analyzed on the basis of the average frequency and the rise angle of the waveforms. It was observed that the Felicity ratio gradually decreased with the increase in the stress level, which showed a cumulative damage effect. From the perspective of energy, the obvious increase of AE energy rate was mainly concentrated in the early and late stages of uniaxial compression, while the significant increase of dissipated energy rate occurred in the late stage of uniaxial compression. During the cyclic loading and unloading, most of the work done by external forces in the compaction stage and the elastic stage was converted into elastic strain energy, and dissipated energy began to gradually increase in the stage of stable fracture development. In addition, it was found that the damage evolution of the rock samples changed from slow to fast, and the dissipated energy ratio increased when failure was approaching.

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