Analysis of fracture deformation field and energy evolution of granite after high confining pressure cyclic load pre-damage

Considering the recent developments of deep mining, investigating the rock properties under high ground stress periodic load is highly demanded. Studies show that these characteristics are important factors affecting the long-term steadiness of rock. However, the mechanical properties of rock mass without macro failure after cyclic load should be studied. In the present study, granite in a mine is considered as the research object. A rock pre-damage experiment is conducted with the same cycles under different confining pressures and constant cycle upper and lower limit loads. The pre-damaged rock sample is subjected to a uniaxial compression test, and a high-speed charge couple device camera is used to record the speckle field image of the sample surface during the whole loading process. The digital speckle techniques are used to analyse the image of the pre-damaged sample, the deformation field of the specimen surface, the displacement dislocation value of the localized deformation area and the deformation energy value of the specimen surface. The results show that for the same cycle times, the confining pressure is less than 80 MPa, which has a weakening effect on the rock's axial strength. As the confining pressure approaches 120 MPa, the pre-damaged rock uniaxial peak strength increases. The characteristics of displacement dislocation energy evolution of the localized deformation bound are divided into three stages (pre-peak stage, peak point and post-peak stage). After pre-damage under the same cycle times and different confining pressure conditions, the deformation field evolution of rock is relatively consistent.


Recommendation?
Accept with minor revision (please list in comments)

Comments to the Author(s)
This manuscript shows a comprehensive lab study to probe the energy characteristics of granite due to cyclic loading. The test is well designed and conducted and results of which can provide an in-depth understanding of the mechanical behaviour of rock, thereby providing guidance for underground rock engineering construction and applications. The manuscript is publishable prior to some improvements -please see the comments below.
1、The third item "loading in the form of sine wave" in the test scheme, the specific parameters are unknown, which has a great impact on the experimental results, so the specific experimental parameters should be given. 2、Fig 1 is not clear, please make it larger -It is a little bit hard for me to pick up key information. 3、In the method section, it is unclear what is stress level applied on your sample in the cyclic load. 4、Please modify the format of the formula in the text, such as in Formula 1 and 2 need to be italicized uniformly.
1. In the section '2.1 High confining pressure cyclic load pre-damage test', the author is requested to complete the data for Groups A2, A3, A4 and B in the format of Group A1 in Table 1. 2. In the section '3.1 Analysis of the pre-damage degree of high confining pressure cyclic load', as can be seen in Table 2, the degree of damage of rock increases as the confining pressure increases from 50mpa to 80mpa; while the degree of damage of rock decreases as the confining pressure increases from 80mpa to 100mpa; and the degree of damage of rock remains essentially unchanged as the pressure increases from 100mpa to 120mpa, for which the authors are asked to briefly explain. 3. In the section '3.2 Strain evolution during cyclic loading', from the trend of the change of the ratio of elastic strain to strain under different confining pressure in Figure 7, it can be seen that when the confining pressure is 50Mpa, 80Mpa and 100Mpa separately, the ratio of circumferential elastic strain to circumferential strain has a more obvious linear relationship; however, when the confining pressure is increased to 120Mpa, the ratio of circumferential elastic strain to circumferential strain no longer has a linear relationship and fluctuates greatly, does this indicate that the rock has already undergone macroscopic breakage at this time, please briefly explain by the author. 4. In the section '3.4 Dislocation of the pre-damaged specimen', Figure 12 plots the deformation energy density evolution curve, which shows the process of energy release and energy accumulation of the specimen. When the energy accumulation reaches a maximum, a sudden release of energy occurs and the specimen is not undergoing energy accumulation, does it imply that the rock mass no longer has a bearing capacity at this point. 5. There are many verbose expressions in the paper, so the article content should be modified.

Decision letter (RSOS-201966.R0)
We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.

Dear Dr Yang
On behalf of the Editors, we are pleased to inform you that your Manuscript RSOS-201966 "Analysis of fracture deformation field and energy evolution of granite after high confining pressure cyclic load pre-damage" has been accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referees' reports. Please find the referees' comments along with any feedback from the Editors below my signature.
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Thank you for submitting your manuscript to Royal Society Open Science and we look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch. Comments to the Author(s) This manuscript shows a comprehensive lab study to probe the energy characteristics of granite due to cyclic loading. The test is well designed and conducted and results of which can provide an in-depth understanding of the mechanical behaviour of rock, thereby providing guidance for underground rock engineering construction and applications. The manuscript is publishable prior to some improvements -please see the comments below.
1、The third item "loading in the form of sine wave" in the test scheme, the specific parameters are unknown, which has a great impact on the experimental results, so the specific experimental parameters should be given. 2、Fig 1 is not clear, please make it larger -It is a little bit hard for me to pick up key information. 3、In the method section, it is unclear what is stress level applied on your sample in the cyclic load. 4、Please modify the format of the formula in the text, such as in Formula 1 and 2 need to be italicized uniformly.
I think this paper is very interesting. If the above questions can be revised, I will recommend this paper to be published.
Reviewer: 2 Comments to the Author(s) Overall, this is a good article.The pre-damaged rock sample is subjected to a uniaxial compression test, and a high-speed charge couple device camera is used to record the speckle field image of the sample surface during the whole loading process. The digital speckle techniques are utilized for analyzing the image of the pre-damaged sample, the deformation field of the specimen surface, the displacement dislocation value of the localized deformation area, and the deformation energy value of the specimen surface. In response to this manuscript, the following questions are raised, and the author is expected to reply. 1. In the section '2.1 High confining pressure cyclic load pre-damage test', the author is requested to complete the data for Groups A2, A3, A4 and B in the format of Group A1 in Table 1. 2. In the section '3.1 Analysis of the pre-damage degree of high confining pressure cyclic load', as can be seen in Table 2, the degree of damage of rock increases as the confining pressure increases from 50mpa to 80mpa; while the degree of damage of rock decreases as the confining pressure increases from 80mpa to 100mpa; and the degree of damage of rock remains essentially unchanged as the pressure increases from 100mpa to 120mpa, for which the authors are asked to briefly explain. 3. In the section '3.2 Strain evolution during cyclic loading', from the trend of the change of the ratio of elastic strain to strain under different confining pressure in Figure 7, it can be seen that when the confining pressure is 50Mpa, 80Mpa and 100Mpa separately, the ratio of circumferential elastic strain to circumferential strain has a more obvious linear relationship; however, when the confining pressure is increased to 120Mpa, the ratio of circumferential elastic strain to circumferential strain no longer has a linear relationship and fluctuates greatly, does this indicate that the rock has already undergone macroscopic breakage at this time, please briefly explain by the author. 4. In the section '3.4 Dislocation of the pre-damaged specimen', Figure 12 plots the deformation energy density evolution curve, which shows the process of energy release and energy accumulation of the specimen. When the energy accumulation reaches a maximum, a sudden release of energy occurs and the specimen is not undergoing energy accumulation, does it imply that the rock mass no longer has a bearing capacity at this point. 5. There are many verbose expressions in the paper, so the article content should be modified.

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See Appendix A.
Decision letter (RSOS-201966.R1) We hope you are keeping well at this difficult and unusual time. We continue to value your support of the journal in these challenging circumstances. If Royal Society Open Science can assist you at all, please don't hesitate to let us know at the email address below.
Dear Dr Yang, It is a pleasure to accept your manuscript entitled "Analysis of fracture deformation field and energy evolution of granite after high confining pressure cyclic load pre-damage" in its current form for publication in Royal Society Open Science.
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Dear editor：
Thank you for your useful comments and suggestions on the language and the structure of our manuscript. We have modified the manuscript accordingly, and the detailed corrections are listed below point by point: Response to comments on"Analysis of fracture deformation field and energy evolution of granite after high confining pressure cyclic load pre-damage(RSOS-201966)" Reviewer: 1 1、The third item "loading in the form of sine wave" in the test scheme, the specific parameters are unknown, which has a great impact on the experimental results, so the specific experimental parameters should be given. Answer: It had been revised according to the reviewer's opinions. Experimental parameter setting is added 2、Fig 1 is not clear, please make it larger -It is a little bit hard for me to pick up key information.
Answer: It had been revised according to the reviewer's opinions. The picture is processed clearly and enlarged.
3、In the method section, it is unclear what is stress level applied on your sample in the cyclic load.
Answer: In order to keep the rock from being damaged during the cycle, the uniaxial compressive strength of rock is chosen as the axial loading stress, and it is also discussed in detail.
4、Please modify the format of the formula in the text, such as in Formula 1 and 2 need to be italicized uniformly. Answer: It had been revised according to the reviewer's opinions.
Reviewer: 2 1. In the section '2.1 High confining pressure cyclic load pre-damage test', the author is requested to complete the data for Groups A2, A3, A4 and B in the format of Group A1 in Table 1. Answer: It had been revised according to the reviewer's opinions. Experimental data are added in Table 1. 2. In the section '3.1 Analysis of the pre-damage degree of high confining pressure cyclic load', as can be seen in Table 2, the degree of damage of rock increases as the confining pressure increases from 50mpa to 80mpa; while the degree of damage of rock decreases as the confining pressure increases from 80mpa to 100mpa; and the degree of damage of rock remains essentially unchanged as the pressure increases from 100mpa to 120mpa, for which the authors are asked to briefly explain. Answer: It had been revised according to the reviewer's opinions. Under the experimental conditions, when the confining pressure is less than 80 MPa, the confining pressure weakens the strength of