scholarly journals Study on Electric-Magnetic-Acoustic Signal Regularity and Its Correlation during Rock Shear Failure

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Huilin Jia ◽  
Yue Niu ◽  
Xiaofei Liu ◽  
Enyuan Wang
Keyword(s):  
Acoustic Signal ◽  
Damage Evolution ◽  
Shear Failure ◽  
Tracking System ◽  
Correlation Coefficients ◽  
Coupling Model ◽  
Electric Signal ◽  
Rock Materials ◽  
Coal Rock ◽  
Electric Signals

http://mts.hindawi.com/update/) in our Manuscript Tracking System and after you have logged in click on the ORCID link at the top of the page. This link will take you to the ORCID website where you will be able to create an account for yourself. Once you have done so, your new ORCID will be saved in our Manuscript Tracking System automatically."?>During mining activities, the deformation and damage of coal rock materials might result in coal rock dynamic disasters, such as rock burst. It leads to serious casualties and property losses. Generally, the occurrence of dynamic failure of coal and rock are caused by shear failure of coal seam. Geophysics signals are generated and related to damage evolution in this loading process. In this paper, sandstone samples were subjected to shear failure laboratory experiments, and the electric-magnetic-acoustic signal regularity was measured and analyzed comparatively. The results indicated magnetic signals were more correlated with stress and acoustic emission (AE) signals, while the amplitude of electric signal fluctuation was larger when main failure occurred. With the increase of sample size and shear strength, the strength of electric-magnetic-acoustic signals increased. The correlation coefficients between the magnetic signal and stress as well as AE energy were superior to those of electric signals. The coupling model between AE and electric signals was established, which shows good statistical correlation. This study lays the foundations for further interpreting the generation mechanism of the electric signal. It provides a new method to indicate the damage evolution of coal rock materials.

Numerical modelling of the crack-pore interaction and damage evolution behaviour of rocklike materials with pre-existing cracks and pores

2020 ◽  
pp. 105678952098387
Author(s):  
PLP Wasantha ◽  
D Bing ◽  
SQ Yang ◽  
T Xu
Keyword(s):  
Principal Stress ◽  
Damage Evolution ◽  
Shear Failure ◽  
Mechanical Response ◽  
Distribution Patterns ◽  
Stress Distributions ◽  
Compressive Stresses ◽  
Major Principal Stress ◽  
The Right ◽  
Macroscopic Failure

The combined effect of pre-existing cracks and pores on the damage evolution behaviour and mechanical properties of rocklike materials under uniaxial compression was numerically studied. Simulations of cracks and pores alone showed that increasing crack length and pore diameter decrease uniaxial compressive strength (UCS) and elastic modulus. Subsequent simulations considered two types of combinations of pre-existing cracks and pores – two cracks either side of a centric pore, and two pores either side of a centric crack – and the distance between cracks and pores was changed. In the case of two cracks at either side of the pore, UCS increased only slightly when the distance between the cracks and pore was increased. This was attributed to the more profound effect of the presence of the pore on UCS, and was confirmed by the progressive crack development characteristics and the major principal stress distribution patterns, which showed that the cracks initiated from the tips of the two pre-existing cracks made little or no contribution to the ultimate macroscopic failure. In contrast, models with two pores at either side of a centric crack showed a marked dependency of UCS on the distance between the pores and the crack. Cracks propagating from pre-existing pores made a greater contribution to the ultimate macroscopic failure when the pores were close to the centric crack and the effect gradually diminished with increasing space between pre-existing pores and the centric crack. Major principal stress distributions showed an asymmetric mobilisation of compressive stresses at the right and left sides of the two pores, favouring macroscopic shear failure when they were close to the centric crack which had led to a lower UCS. Overall, this study presents some critical insights into crack-pore interaction behaviour and the resulting mechanical response of rocklike materials to assist with the design of rock structures.

A numerical approach to predict soil bearing potential for isolated footing

2021 ◽  
Author(s):  
Gilbert Hinge ◽  
Jayanta Kumar Das ◽  
Biswadeep Bharali
Keyword(s):  
Bearing Capacity ◽  
Shear Failure ◽  
Correlation Coefficients ◽  
Failure Criteria ◽  
Numerical Approach ◽  
Ultimate Bearing Capacity ◽  
Foundation Design ◽  
Advantages And Disadvantages ◽  
Local Shear ◽  
Failure Conditions

<p>The success of any civil engineering structure's foundation design depends upon the accuracy of estimation of soil’s ultimate bearing capacity. Numerous numerical approaches have been proposed to estimate the foundation's bearing capacity value to avoid repetitive and expensive experimental work. All these models have their advantages and disadvantages. In this study, we compiled all the governing equations mentioned in Bureau of Indian standard IS:6403-1981 and modify the equation for Ultimate Bearing Capacity. The equation was modified by considering two new parameters, K1(for general shear) and K2 (for local shear) so that a common governing equation can be used for both general and local shear failure criteria. The program used for running the model was written in MATLAB language code and verified with the observed field data. Results indicate that the proposed model accurately characterized the ultimate, safe, and allowable bearing capacity of a shallow footing at different depths. The correlation coefficients between the observed and model-predicted bearing capacity values for a 2m foundation depth with footing size of 1.5 ×1.5, 2.0 × 2.0, and 2.5 × 2.5 m are 0.95, 0.94, and 0.96. A similar result was noted for the other foundation depth and footing size. Findings show that the model can be used as a reliable tool for predicting the bearing capacity of shallow foundations at any given depth.  Moreover, the formulated model can also be used for the transition zone between general and local shear failure conditions.</p>

scholarly journals Experimental Investigation on Time-Frequency Characteristics of Microseismic Signals in the Damage Evolution Process of Coal and Rock

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 809
Author(s):  
Wei Yang ◽  
Chengwu Li ◽  
Rui Xu ◽  
Xunchang Li
Keyword(s):  
Damage Evolution ◽  
Resonance Effect ◽  
Low Frequency ◽  
Dominant Frequency ◽  
Frequency Characteristics ◽  
Evolution Process ◽  
Deformation And Failure ◽  
Time Frequency ◽  
Rock Materials ◽  
Damage Degree

The deformation and failure of coal and rock materials is the primary cause of many engineering disasters. How to accurately and effectively monitor and forecast the damage evolution process of coal and rock mass, and form a set of prediction methods and prediction indicators is an urgent engineering problems to be solved in the field of rock mechanics and engineering. As a form of energy dissipation in the deformation process of coal and rock, microseismic (MS) can indirectly reflect the damage of coal and rock. In order to analyze the relationship between the damage degree of coal and rock and time-frequency characteristics of MS, the deformation and fracture process of coal and rock materials under different loading modes was tested. The time-frequency characteristics and generation mechanism of MS were analyzed under different loading stages. Meanwhile, the influences of properties of coal and rock materials on MS signals were studied. Results show that there is an evident mode cutoff point between high-frequency and low-frequency MS signals. The properties of coal and rock, such as the development degree of the original fracture, particle size and dense degree have a decisive influence on the amplitude, frequency, energy and other characteristic parameters of MS signals. The change of MS parameters is closely related to material damage, but has no strong relation with the loading rate. The richness of MS signals before the main fracture depends on the homogeneity of materials. With the increase of damage, the energy release rate increases, which can lead to the widening of MS signals spectrum. The stiffness and natural frequency of specimens decreases correspondingly. Meanwhile, the main reason that the dominant frequency of MS detected by sensors installed on the surface of coal and rock materials is mainly low-frequency is friction loss and the resonance effect. In addition, the spectrum and energy evolution of MS can be used as a characterization method of the damage degree of coal and rock materials. Furthermore, the results can provide important reference for prediction and early warning of some rock engineering disasters.

The relationship between physical match performance and 48-h post-game creatine kinase concentrations in English Premier League soccer players

2016 ◽  
Vol 11 (6) ◽  
pp. 846-852 ◽  
Author(s):  
A Scott ◽  
JJ Malone ◽  
R Morgans ◽  
D Burgess ◽  
W Gregson ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Tracking System ◽  
Correlation Coefficients ◽  
Soccer Players ◽  
Large Individual ◽  
Premier League ◽  
Coaching Process ◽  
The Relationship ◽  
English Premier League ◽  
Physical Match

The aim of the investigation was to determine the relationship between blood creatine kinase and physical match performance in 15 elite male soccer players competing in the English Premier League. Blood samples were collected 48 h following a competitive match and analysed for creatine kinase concentration immediately after collection. Physical match performance data were collected using a computerised tracking system (Prozone®) from >6 matches for each player. Mean ± S.D creatine kinase concentration 48 h post-match was 520 ± 224 µ.mol.l−1. Large individual variation in creatine kinase response at this time point was observed (184 µ.mol.l−1 to 1573 µ.mol.l−1). No significant correlation coefficients were observed between the chosen indicators of physical match performance and creatine kinase concentration 48 h post-match. These data suggest that creatine kinase concentrations are elevated as a consequence of playing a soccer match. Creatine kinase may also be of limited value in supporting important decisions in the coaching process.

EXPERIMENTAL INVESTIGATION ON MULTI-FRACTAL CHARACTERISTICS OF ACOUSTIC EMISSION OF COAL SAMPLES SUBJECTED TO TRUE TRIAXIAL LOADING–UNLOADING

Fractals ◽  
2020 ◽  
Vol 28 (05) ◽  
pp. 2050092 ◽  
Author(s):  
RAN ZHANG ◽  
JIE LIU ◽  
ZHANYOU SA ◽  
ZAIQUAN WANG ◽  
SHOUQING LU ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Dynamic Changes ◽  
Deformation And Failure ◽  
True Triaxial ◽  
Coal Deformation ◽  
Coal Rock ◽  
True Triaxial Stress ◽  
Fractal Characteristics ◽  
Loading And Unloading ◽  
Precursory Information

Coal–rock dynamic disasters seriously threaten safe production in coal mines, and an effective early warning is especially important to reduce the losses caused by these disasters. The occurrence of coal–rock dynamic disasters is determined by mining-induced stress loading and unloading. Therefore, it is of great significance to analyze the precursory information of coal deformation and failure during true triaxial stress loading and unloading. In this study, the deformation and failure of coal samples subjected to true triaxial loading and unloading, including fixed axial stress and unloading confining stress (FASUCS), are experimentally investigated. Meanwhile, acoustic emission (AE) during the deformation of coal samples is monitored, and the multi-fractal characteristics of AE are analyzed. Furthermore, combined with the deformation and failure of coal samples, the precursory information of coal deformation and rupture during true triaxial stress loading and unloading is obtained. Finally, the relationship between multi-fractal characteristics and damage evolution of coal samples under FASUCS is discussed. The results show that the multi-fractal spectral widths of AE time series under the conditions of FASUCS with different initial confining stresses or unloading rates are quite different, but the dynamic changes of multi-fractal parameters [Formula: see text] and [Formula: see text] are similar. This indicates that the microscopic complexity of AE events of coal samples under different conditions of FASUCS differs, but the macroscopic generation mechanism of AE events has inherent uniformity. The dynamic changes of [Formula: see text] and [Formula: see text] can reflect the stress and damage degree of coal samples. The dynamic change process of [Formula: see text] well accords with the damage evolution process of coal samples. A gradual decrease of [Formula: see text] corresponds to a slow increase of damage, while a sharp increase of it corresponds to a rapid growth of damage. At the same time, the mutation point of damage curve at distinct stress difference levels shares the same variation trend with the [Formula: see text] mutation point. The change of [Formula: see text] can reflect the damage process of coal samples, which can be used as precursor information for predicting coal–rock rupture. The finding is of great significance for the early warning of coal–rock dynamic disasters.

scholarly journals Fabrication of Si3N4-Based Artificial Basilar Membrane with ZnO Nanopillar Using MEMS Process

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Jun-Hyuk Kwak ◽  
Youngdo Jung ◽  
Kyungjun Song ◽  
Shin Hur
Keyword(s):  
Sound Wave ◽  
Basilar Membrane ◽  
Local Deformation ◽  
Electric Signal ◽  
Bottom Substrate ◽  
Specific Frequency ◽  
Acoustic Device ◽  
Artificial Basilar Membrane ◽  
Electric Signals ◽  
Mems Process

This paper presents the fabrication of Si3N4-based artificial basilar membrane (ABM) with ZnO nanopillar array. Structure of ABMs is composed of the logarithmically varying membrane fabricated by MEMS process and piezonanopillar array grown on the Si3N4-based membrane by hydrothermal method. We fabricate the bottom substrate containing Si3N4-based membrane for inducing the resonant motions from the sound wave and the top substrates of electrodes for acquiring electric signals. In addition, the bonding process of the top and bottom substrate is performed to build ABM device. Depending on sound wave input of the specific frequency, specific location of the ABM produces a resonant behavior. Then a local deformation of the piezonanopillar array produces an electric signal between top and bottom electrode. As experimental results of the fabricated ABM, the measured resonant frequencies are 2.34 kHz, 3.97 kHz, and 8.80 kHz and the produced electrical voltages on each resonant frequency are 794 nV, 398 nV, and 89 nV. Thus, this fabricated ABM device shows the possibility of being a biomimetic acoustic device.

scholarly journals Investigations of Coal-Rock Parting-Coal Structure (CRCS) Slip and Instability by Excavation

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Guang-Jian Liu ◽  
Heng Zhang ◽  
Ya-Wei Zhu ◽  
Wen-Hao Cao ◽  
Xian-Jun Ji ◽  
...  
Keyword(s):  
Shear Failure ◽  
P Wave ◽  
Shear Behaviour ◽  
Failure Zone ◽  
Stick Slip ◽  
Coal Structure ◽  
P Wave Velocity ◽  
Splitting Failure ◽  
Shear And Tensile Cracks ◽  
Coal Rock

Slip and instability of coal-rock parting-coal structure (CRCS) subjected to excavation disturbance can easily induce coal-rock dynamic phenomena in deep coal mines. In this paper, the failure characteristics and influencing factors of CRCS slip and instability were investigated by theoretical analysis, numerical simulations, and field observations. The following main results are addressed: (1) the slip and instability of CRCS induced by excavation are due to stress release, and the damage of the rock parting is partitioned into three parts: shear failure zone, slipping zone, and splitting failure zone from inside to outside with slip; (2) the slip and instability process of CRCS is accompanied by initiation, expansion, and intersection of shear and tensile cracks. The development of the cracks is dominated by shear behaviour, while the tensile crack is the main factor affecting fracture and instability of CRCS; and (3) slip and instability of CRCS are characterized by stick-slip first and then stable slip, accompanied with high P-wave velocity and rockburst danger coefficient based on microseismic tomography.

Loudspeaker system for converting a digitized electric signal into an acoustic signal

1989 ◽  
Vol 85 (1) ◽  
pp. 530-530
Author(s):  
Joris A. M. Nieuwendijk ◽  
Wilhelmus D. A. M. Van Gijsel
Keyword(s):  
Acoustic Signal ◽  
Electric Signal

Dynamic Template Tracking System with Application to the Detection of the Railway Spike Defects

2013 ◽  
Vol 846-847 ◽  
pp. 1124-1128
Author(s):  
Rong Hu ◽  
Xiao Qing Luo
Keyword(s):  
Tracking System ◽  
Complex Function ◽  
Correlation Coefficients ◽  
Matching Function ◽  
Point Multiplication ◽  
Computation Efficiency ◽  
Traditional Algorithm ◽  
Point To Point ◽  
Real Time Identification ◽  
Dynamic Template

This paper presents a novel correlation-based tracking algorithm, which is a generalization of the dynamic template correlation regional tracking (DTCRT) algorithmthe template is dynamic and the correlation is regional, and in particular the target image quality is not always good. The algorithm does not make use of the point-to-point multiplication and then summarizing as the traditional algorithm does. Instead, the DTCRT algorithm introduced. This fact helps to overcome several shortcomings of the point-to-point multiplication and then summarizing. The target is represented by the correlation coefficients. If the correlation coefficient is less than a threshold one can judge then the spike is defected. Since the matching function is a very complex function, the DTCRT algorithm is used to optimize it. Experiments demonstrate the effectiveness, significance and computation efficiency of the proposed railway spike tracking method in real-time identification.

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