Modified Model and Simulation Verification of Rock-Fatigue Damage Considering Repeated Discharge Impact
Round 1
Reviewer 1 Report
Dear Authors,
You have presented theory, formulations, real test results, and numerical results. The combination of all these is a difficult task for any author, especially to get a good balance of details in all such that the reader can follow the work. I believe that you have done a nice job with the background, theory and formulation. However I have the following major concerns:
1) At times the English language is good and at other times it not sufficient for publication. I recommend that the article be reviewed by an editing service or someone fluent in English. This is a concern because at times I am uncertain if it there are English language issues that impact the accuracy of statements or if there is a bigger concern about the authors understanding of rock damage and cracking process. I assume that it is the former, however, an example comes in the first paragraph of the Introduction "When the damage accumulates to a certain extent, defects such as micro cracks will be formed". Damage is caused by micro-cracks. So once you have damage you have micro-cracks and visa versa. It is not that damage accumulates until micro-cracks form, what happens is that the strain or stress accumulates until damage occurs. The damage is manifest as the micro-cracks. So the statement you wrote is not accurate. The question is why? Another example in the same paragraph, "eventually lead to the 30 weakening of the rock strength and failure." You reduce the rock strength through weakening processes. the statement "weakening of the rock strength" is not accurate. you can weaken the rock and reduce its strength. reduce is the more appropriate word.
There are many more places in the text that the English language detracts from understanding the true meaning of the statements in the paper.
2) The theory and equations are well laid out in the paper, although the authors need to ensure that all parameters in all formulas are described well. Constants should be describe in terms of how they were determined and ranges of typical key values could be provided particularly for sandstones if you have them.
3) What is unclear is how you determined the values shown in Figure 4. You say "formula 21" was used, however, there is no equation 21. If you mean equation 19, than you do not describe the process by which you determined say the radius length, etc. from the real lab tests. How does the reader know that the values you determined from theory are accurate? Can you compare those you derive from the real lab tests with the work of the authors that developed the equation on radius for example, such that the reader can see for themselves how accurate the theory and formulations are? You need to build trust in the theory somehow. It is not sufficient to say show the variation of lab results with discharge times and energy but you also need to demonstrate that the background theory has been applied accurately to your own lab results.
4) The model needs to be describe in more detail. What are the influencing parameters that you had to calibrate? What is the influence of the mesh on the results? You jump very quickly to model results, perhaps too quickly for the reader to appreciate the hard work that is needed to develop the model. You show the error between the calculated and simulated values, but not the real values. Can you determine the real crack densities in the samples or examine crack dimensions directly through scans or thin sections. This would be ideal to demonstrate either the calculations or simulations or both are accurate. The simulation is based on the theory, so it should align, but the real lab results are what needs to be compared to the theory and model better.
The number of changes is too extensive work for a reviewer of the manuscript. The work needs a thorough edit from someone or an agency before it is suitable for a reviewer to provide feedback on the quality.
Author Response
Dear reviewer, the content of your review comments we have replied to is attached. Please refer to it and thank you for your suggestions and assistance.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this paper, based on the existing damage constitutive model, the sandstone discharge impact experiment was carried out, and the constitutive model considering the dynamic changes of rock mechanics properties and the geometric size of microcracks was established. Although underwater discharge impact technology has been widely applied in the field of oil and gas field development, the fatigue damage model of repeated discharge on rock failure has not been deeply explored. This paper needs to be slightly revised before acceptance.
(1) The paper involves many formulas. It should be clear which are for reference and which are derived by the author. Relevant references should be cited.
(2) The rock compressive strength values at different discharge energy and discharge times are obstructed by acoustic wave test "in Page 14 How the authors converted wave velocity into compressive strength should be introduced in detail.
(3) What does "1.26 cracks" effectively mean in Table 5?
(4) It is suggested that the author added the innovative description of this paper in the introduction and conclusion.
(5) The quality of the English need to be improved.
The quality of the English need to be improved.
Author Response
Dear reviewer, the content of your review comments we have replied to is attached. Please refer to it and thank you for your suggestions and assistance.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper studied rock fatigue damage considering repeated discharge impact and achieved some conclusions. Nevertheless, I encourage the authors to take the following points into account and make the appropriate and necessary revisions carefully.
1. In “Introduction”, the application background of discharge should be clearly explained. The more damage models should be referenced and learned.
2. In line 98, Eq. 4 and Eq. 8, the alphabetic symbol “a” and “α” should be unified.
3. In line 91, there should be a reference of the Eq. 3.
4. In line 123 and Eq. 7, the alphabetic symbol “ak” and “αk”, “nk” and “nk” should be unified.
5. In line 132, there noted that “Kawamoto modified the above model by introducing crack pressure transfer and shear transfer coefficient to consider the characteristics those joints that can transfer partial compressive stress and shear stress under compressive load.”, the formula should be listed here.
6. In line 193-201, the statement is in reverse order.
7. In the section of “Test Scheme”, the detailed test procedure needs to be explained clearly.
8. In table 1, what is the “Core” mean? There should be added the porosity and permeability before discharge. Where is the discharge number?
9. In table 2, the rock compressive strength enlarged after discharge damaged??
10. In line 279, there noted that “the corresponding calculation results are obtained by modifying the model calculation formula 21”, where is the formula 21??
11. In table 3, the “Young's modulus E is 18 MPa”, but the value is about 8619.1 MPa in table 1, the gap between the two values is too wide??
12 In Figure 4. (d), the damage value D, according to Eq. 2~6, the value of D should between 0~1, but the value in the figure is more than 1, this should be explained.
13. In section 4.1, the boundary conditions and parameters should be added.
The English is generally good.
Author Response
Dear reviewer, the content of your review comments we have replied to is attached. Please refer to it and thank you for your suggestions and assistance.
Author Response File: Author Response.pdf
