Uniaxial compression test of rocks: Review of strain measuring instruments

Isah, Balarabe Wada; Mohamad, Hisham; Ahmad, Niraku Rosmawati; Harahap, Indra Sati Hamonangan; Al-Bared, Mohammed Ali Mohammed

doi:10.1088/1755-1315/476/1/012039

Cited by 8 publications

(4 citation statements)

References 8 publications

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“…These power laws signify the distribution and organization of various components or phenomena at different scales within the system as a manner to release the excess injected energy. Thus, the application of these principles leads to Equation (15), which provides an analytical relationship indicating that an increase in rock electrification is accompanied by a decrease in the b-value. Moreover, Equation (10) demonstrates that the b-value exhibits proportionality to the thermodynamic fractal dimension, contingent upon whether the dominant energy dissipation occurs at the large scale or the small scale.…”

Section: Discussionmentioning

confidence: 99%

“…Figure 3a illustrates the relationship between the b-value and the macroscopic entropy change through 𝐽 ̂𝑒, represented by the green curve. As indicated by Equation (15) (shown by the red curve in Figure 3a), the green curve indicates a negative correlation between the b-value and the increase in electromagnetic signals. Hence, the negative correlation between the b-value and electromagnetic signals is a result of the multiscale entropy change, as Equation ( 2) encompasses the derivation of both.…”

Section: Electromagnetic Emission and B-value Relationship: The Physi...mentioning

confidence: 96%

“…As stress increases, the material may begin to collapse internally by creating microcracks that follow a fractal pattern. These microcracks continue to grow until they result in macroscopic failure that is also self-similar [9][10][11][12][13][14][15][16][17][18][19][20]. As microcracks grow, they release energy in the form of acoustic emissions and electromagnetic signals.…”

Section: Introductionmentioning

confidence: 99%

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Analytical Relation between b-Value and Electromagnetic Signals in Pre-Macroscopic Failure of Rocks: Insights into the Microdynamics’ Physics Prior to Earthquakes

Venegas-Aravena

Cordaro

2023

Geosciences

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Field measurements in subduction regions have revealed the presence of non-seismic pre-earthquake signals such as electromagnetic or acoustic emission, gas liberation, changes in Earth’s surface temperature, changes at the ionospheric level, or fluid migration. These signals are commonly associated with impending earthquakes, even though they often rely solely on temporal and spatial correlations in impending earthquake zones without a comprehensive understanding of the underlying lithospheric processes. For example, one criticism is the measurement of increasing electromagnetic signals even in the absence of observable macroscopic stress changes, which challenges the conventional understanding that macroscopic stress changes are the primary energy source for non-seismic pre-earthquake signals. To address this gap, rock experiments provide valuable insights. Recent experiments have shown that rocks can become electrified under constant macroscopic stress changes, accompanied by a decrease in the b-value, indicating multiscale cracking. This suggests the existence of small-scale dynamics that generate electromagnetic signals independently of large-scale stress variations. In that sense, multiscale thermodynamics offers a valuable perspective in describing this multiscale phenomenon. That is why the main goal of this work is to demonstrate that the electromagnetic signals before macroscopic failures are not independent of the cracking generation because the origin of both phenomena is the same. In particular, we present analytical equations that explain the physical connection between multiscale cracking, the generation of electromagnetic signals, and its negative correlation with acoustic emission before the macroscopic failure of rocks even when the macroscopic load is constant. In addition, we also show that the thermodynamic fractal dimension, which corresponds to the global parameter that controls the cracking process, is proportional to the b-value when the large-scale crack generation is considerably larger than the small-scale cracks. Thus, the decreases in the b-value and the increases in the electromagnetic signals indicate that rocks irreversibly prepare to release energy macroscopically. These findings could be related to the dynamics at lithospheric scales before earthquakes.

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Section: Discussionmentioning

confidence: 99%

Section: Electromagnetic Emission and B-value Relationship: The Physi...mentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Analytical Relation between b-Value and Electromagnetic Signals in Pre-Macroscopic Failure of Rocks: Insights into the Microdynamics’ Physics Prior to Earthquakes

Venegas-Aravena

Cordaro

2023

Geosciences

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“…The principle of UCS involves placing cylindrical samples or prepared drill cores under axial loading until the failure moment in a uniaxial compression test (UCT) device. Figure 1 illustrates a conventional rock UCT machine [30]. The UCT is used for the determination of the ultimate UCS values.…”

Section: Laboratory Studiesmentioning

confidence: 99%

Support Vector Machine (SVM) Application for Uniaxial Compression Strength (UCS) Prediction: A Case Study for Maragheh Limestone

et al. 2023

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The geomechanical properties of rock materials, such as uniaxial compression strength (UCS), are the main requirements for geo-engineering design and construction. A proper understanding of UCS has a significant impression on the safe design of different foundations on rocks. So, applying fast and reliable approaches to predict UCS based on limited data can be an efficient alternative to regular traditional fitting curves. In order to improve the prediction accuracy of UCS, the presented study attempted to utilize the support vector machine (SVM) algorithm. Multiple training and testing datasets were prepared for the UCS predictions based on a total of 120 samples recorded on limestone from the Maragheh region, northwest Iran, which were used to achieve a high precision rate for UCS prediction. The models were validated using a confusion matrix, loss functions, and error tables (MAE, MSE, and RMSE). In addition, 24 samples were tested (20% of the primary dataset) and used for the model justifications. Referring to the results of the study, the SVM (accuracy = 0.91/precision = 0.86) showed good agreement with the actual data, and the estimated coefficient of determination (R2) reached 0.967, showing that the model’s performance was impressively better than that of traditional fitting curves.

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Fracturing Processes in Specimens with Internal vs. Throughgoing Flaws: An Experimental Study Using 3D Printed Materials

Almubarak,

Germaine,

Einstein

2024

Rock Mech Rock Eng

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The fracturing behavior and associated mechanical characterization of rocks are important for many applications in the fields of civil, mining, geothermal, and petroleum engineering. Laboratory testing of rocks plays a major role in understanding the underlying processes that occur on the larger scale and for predicting rock behavior. Fracturing research requires well-defined and consistent boundary conditions. Consequently, the testing design and setup can greatly influence the results. In this study, a comprehensive experimental program using an artificial material was carried out to systematically evaluate the effects of different parameters in rock testing under uniaxial compression. The parameters include compression platen type, specimen centering, loading control method, boundary constraints, and flaw parameters. The results show that these testing conditions have a significant effect on the mechanical behavior of rocks. Using a fixed compression platen helped reduce bulging of the material. Centering of the specimen played a critical role to avoid buckling and unequal distribution of stress. Slower displacement rates can control the energy being released once failure occurs to prevent the specimen from exploding. Also, the frictional end effects were investigated by comparing friction-reduced and non-friction-reduced end conditions. Very importantly, the study also identified variations in crack initiation and propagation between specimens with internal flaws and specimens with throughgoing flaws. This investigation showed that wing cracks appeared in specimens with throughgoing flaws, while wing cracks with petal cracks were associated with the internal flaws. It also showed that the mechanical properties are influenced by the inclination of the flaws and established that specimens with internal flaws generally exhibit higher strength compared to specimens with throughgoing flaws. The systematic analysis presented in this work sheds light on important considerations that need to be taken into account when conducting fracture research and adds knowledge to the fundamental understanding of how fractures occur in nature.

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Uniaxial compression test of rocks: Review of strain measuring instruments

Cited by 8 publications

References 8 publications

Analytical Relation between b-Value and Electromagnetic Signals in Pre-Macroscopic Failure of Rocks: Insights into the Microdynamics’ Physics Prior to Earthquakes

Analytical Relation between b-Value and Electromagnetic Signals in Pre-Macroscopic Failure of Rocks: Insights into the Microdynamics’ Physics Prior to Earthquakes

Support Vector Machine (SVM) Application for Uniaxial Compression Strength (UCS) Prediction: A Case Study for Maragheh Limestone

Fracturing Processes in Specimens with Internal vs. Throughgoing Flaws: An Experimental Study Using 3D Printed Materials

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