Variation of Elastic Stiffness Parameters of Granitic Rock during Loading in Uniaxial Compressive Test
Round 1
Reviewer 1 Report
After reading the paper "Variation of Elastic Stiffness Parameters of Rock During Loading in Uniaxial Compressive Test", I can say that it is a high quality paper that will be of interest to the readers of Applied Mechanics will find interesting.
There are only minor deficiencies that need to be corrected before publication, namely:
Line 112: In Figure 2, the "crack closure" area" is unrealistically large. It is not that large for any rock material!
Line 154: I think this paragraph should be expanded to include the paper here https://doi.org/10.17794/rgn.2022.3.7
Lines 182 to 187: This paragraph also needs to be expanded to include more recent papers such as https://www.mdpi.com/2076-3417/11/13/6148
Line 340: The R2 values are wrong! They need to be 0.6 and 0.57. Also, no references are given in the conclusion, so it should be deleted [27].
Good luck!
Author Response
Thank you for agreeing to review our manuscript. We have clarified the vague parts in mentioned sentences. We greatly appreciate your contribution and time, which assisted authors in disseminating their work at the highest possible quality.
- Line 112: In Figure 2, the "crack closure" area" is unrealistically large. It is not that large for any rock material!
ANSWER: It’s corrected.
- Line 154: I think this paragraph should be expanded to include the paper here https://doi.org/10.17794/rgn.2022.3.7
ANSWER: It’s corrected.
Furthermore, Davarpanah et al. [21] reviewed in great detail the impact of freezing on fundamental mechanical properties, such as Young's modulus, by determining density, ultrasound speed propagation, and strength parameters, and they discovered that Young's modulus rises as the temperature falls.
Lines 182 to 187: This paragraph also needs to be expanded to include more recent papers such as https://www.mdpi.com/2076-3417/11/13/6148
ANSWER: It’s corrected.
In order to provide a reasonable estimate of the Young's Modulus of grain-supported carbonates rocks, Brievac et al. [24] used machine learning technology and took into account petrographic characteristics; however, they did not look into the variation of E.
- Line 340: The R2values are wrong! They need to be 0.6 and 0.57. Also, no references are given in the conclusion, so it should be deleted [27].
ANSWER: It’s corrected.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This is a very interesting manuscript. Based on the UCS experimental results, it proposed a new method to estimate the elastic stiffness properties of intact granite rocks. This opens up new ideas for researchers to study other mechanical properties of rock. I think it can be published after revision.
1. Introduction: The introduction only explains the common problems existing in current rock mechanics experiments, and too little is explained for others' research in this area. It is recommended to add some research by others to highlight the importance and necessity of this research.
2. Methods and Results: Please briefly introduce your experimental process, which is not introduced in the full manuscript. In addition, only one experimental result was used in multiple images to illustrate the problem, which I think is not rigorous enough. It is recommended to add several sets of experimental results to support your discussion.
3. Section 2.1: Table 1 and Table 2 show the value ranges of some data. Can you briefly explain the basis of the value ranges of these data?
4. Section 2.2: It showed several different curves in Figures 5-7, but the introduction of the curves was missing, please add them.
5. Discussion: Please briefly explain the significance of the current research work, as well as the future research work and direction.
6. The title of this manuscript is “Variation of Elastic Stiffness Parameters of Rock During Loading in Uniaxial Compressive Test”. However, the full text experiment only used granite, which cannot represent all rocks. Suggest revising the title.
Author Response
Thank you for agreeing to review our manuscript. We have modified the abstract and included numeric results. We have stated the significance of the research. We greatly appreciate the dedication of reviewers like you; it would be impossible to manage an efficient peer review process and maintain the high standards necessary for a successful journal.
- Introduction: The introduction only explains the common problems existing in current rock mechanics experiments, and too little is explained for others' research in this area. It is recommended to add some research by others to highlight the importance and necessity of this research.
ANSWER: Since there is no research works on this topic, it is quite difficult to cite any similar studies. However, other researches are mentioned in the methodology part of the manuscript from line 161 to 205.
- Methods and Results: Please briefly introduce your experimental process, which is not introduced in the full manuscript. In addition, only one experimental result was used in multiple images to illustrate the problem, which I think is not rigorous enough. It is recommended to add several sets of experimental results to support your discussion.
ANSWER: The tests were conducted using a computer-controlled servo-hydraulic machine that was set to operate in continuous load control mode. During the tests, the samples were loaded with a high level of precision, with an accuracy of 0.01 kN and at a constant rate of 0.6 kN/s. To measure the deformations experienced by the samples, both axial and lateral, strain gauges were utilized. It's worth noting that the cylindrical rock samples adhered to the L/D ratio of 2/1, where L represented the length and D represented the diameter of each sample. In total, seventeen uniaxial compressive tests were performed in the rock mechanics laboratory [11].
In this study we have tested 17 specimens and the plotted graphs are the typical.
- Section 2.1: Table 1 and Table 2 show the value ranges of some data. Can you briefly explain the basis of the value ranges of these data?
ANSWER: According to analysis of seventeen samples of UCS test, the range of the constants of a, b and c determined. These constants are rock type dependent.
- Section 2.2: It showed several different curves in Figures 5-7, but the introduction of the curves was missing, please add them.
ANSWER: The applied method are already explained for this section by using equations 5 and 6 .
- Discussion: Please briefly explain the significance of the current research work, as well as the future research work and direction.
ANSWER: Deformation behavior of intact rock is mainly controlled by development of crack networks. Considering this fact, the propagation of crack in each step of UCS test can be applied with corresponding stiffness behavior.
The future work can be directed to study the effect of confining pressure of the intact rock in the variation of elastic stiffness parameters in triaxial test. Moreover, Poisson’s ratio has a significant impact on the mechanical behavior of intact rock. So, it is necessary to investigate the variation of Poisson’s ratio in UCS test.
- The title of this manuscript is “Variation of Elastic Stiffness Parameters of Rock During Loading in Uniaxial Compressive Test”. However, the full text experiment only used granite, which cannot represent all rocks. Suggest revising the title
ANSWER: The title changed to granitic rocks.
Author Response File: Author Response.docx
Reviewer 3 Report
I have no more questions on this manuscript. Only some formats and grammars are needed to revise.
Author Response
Thank you for agreeing to review our manuscript. The Structure and writing of the paper improved.
Author Response File: Author Response.docx
Reviewer 4 Report
The authors present an interesting and important study aimed at monitoring rock elastic stiffness parameters (Young’s Modulus, Shear Modulus and Bulk Modulus) changes during unconfined compressive strength tests. The variation is monitored from crack closure to the failure stage. The secant, average and tangent values for each of the rock elastic stiffness parameters are analysed. Monitoring the rock elastic stiffness parameters can provide insights into the rock's mechanical behaviour and deformation characteristics. For example, changes in Young's modulus can indicate the degree of rock deformation during the test, while changes in shear modulus can indicate the development and propagation of cracks. It also helps predict the rock's behaviour under different loading conditions. By understanding how these parameters change during the UCS test, engineers and geologists can better predict how the rock will behave under different stresses and strains, such as those experienced during mining or excavation activities Changes in rock elastic stiffness parameters can provide early warning signs of potential rock failure. For example, a decrease in Young's modulus or shear modulus may indicate the development of internal cracks or structural damage, which can lead to rock failure.
The following need to be addressed:
- Rock material Poisson Ratio, for the elastic case, is always greater than 0 but less than 0.5.
- Further clarification is needed for the author’s argument ‘Yet, treating Young's modulus as an elastic constant is a dubious practice because Young's modulus of a rock varies continuously, even during the linear elastic stage’.
- Note that ISRM, as per the latest update, now stands for International Society for Rock Mechanics and Rock Engineering.
- The use of the term ‘unlimited compressive strength’ to refer to uniaxial compressive strength is somewhat misleading as it gives the impression that the rock has unlimited compressive strength. Actually, the strength of a rock increases with confinement (the so-called limitation).
- Some minor language errors were noted. These will be corrected at the production stage of the paper.
Author Response
Thank you for agreeing to review our manuscript. New comments were added. We do greatly appreaciate technical points you mentioned. It helps us to get more inside and deeper understanding of our research.
- Rock material Poisson Ratio, for the elastic case, is always greater than 0 but less than 0.5.
ANSWER: In the manuscript from line 152 to 154 there is mentioned that 'Theoretically, the Poisson’s ratio of isotropic and linear elastic material is a constant between -1 and +0.5. For rock materials it is always positive, and it is between 0.05 and 0.40'.
- Further clarification is needed for the author’s argument ‘Yet, treating Young's modulus as an elastic constant is a dubious practice because Young's modulus of a rock varies continuously, even during the linear elastic stage’
ANSWER: According to our study and analysis, based on the achieved equations and related constants, we can see the variation of Young’s modulus in a nonlinear parabolic function. It proves the idea that even in the linear stage of the curve, the Young’s modulus can be changed.
- Note that ISRM, as per the latest update, now stands for International Society for Rock Mechanics and Rock Engineering.
ANSWER: We changed to ISRMRE.
- The use of the term ‘unlimited compressive strength’ to refer to uniaxial compressive strength is somewhat misleading as it gives the impression that the rock has unlimited compressive strength. Actually, the strength of a rock increases with confinement (the so-called limitation).
ANSWER: We replaced the ‘unlimited compressive strength’ to ‘uniaxial compressive strength’.
- Some minor language errors were noted. These will be corrected at the production stage of the paper.
ANSWER: The Structure and writing of the paper improved.
Author Response File: Author Response.docx
