The Effect of Pore Pressure on the Mechanical Behavior of Coal with Burst Tendency at a Constant Effective Stress
Round 1
Reviewer 1 Report
The interaction between coal and gas and its effect on coal mechanical properties are very important to reveal the mechanism of dynamic disasters in coal mining. The mechanical behaviors of impact tendency coal are investigated by conducting a series of triaxial compression experiments of coal samples. The manuscript should be revised to correct the expression of some concepts and improve the quality of papers. Some suggestions are provided below for author’s consideration.
1) In the Section 2.2, the information of coal samples should be given more details. What is the sampling depth? What are the gas content, pressure and hydrogeological conditions of coal seam respectively? What are the pore size distributions of coal samples monitored by NMR?
2) In the Section 3.1, the axial and radial strains should be given before the volumetric stain are discussed.
3) In the Section 3.2, the elastic modulus and Poisson’s ratio are important mechanical performance indexs which are measured by uniaxial compression testing. The authors can use the different parameters in the analysis of triaxial compression experiments.
4) The analysis on the experiments need improve. For example, the authors used acoustic emission monitoring during the triaxial compression test, and more details of AE test analysis, such as AE signal location, should be given. It is helpful to enhance the manuscript quality.
5) The discussion and conclusions are suggested to relate the findings of manuscript to the prevention and control of coal dynamic disaster.
Author Response
Thanks for your work reviewing my manuscript and helping us improve this work. Following your suggestion, we revised this manuscript carefully, and the detail is listed in the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In general, the experimental process and experimental results are elaborated in detail. The main modification suggestions are as follows:
1. It is not recommended to write the sentence '…i.e., at a constant effective confining pressure.' in the abstract. Please briefly explain the significance of this study in one or two sentences at the end of abstract.
2. The second paragraph of the introduction needs to be more systematic and elaborate the research status in-depth. It only refers to less than ten papers（[12-20]）. The research significance of this article should also be explained.
3. The thickness and distribution of No.4 coal seam need a brief introduction.
4. The principle of sample number preparation should be noted in Table 1 or clearly stated in the text. Is the sample number '-9-1' missing 'Z'?
5. In Figure 2, a sampling point is not marked. The representation meaning of Fig.2b should be briefly explained in the figure.
6. The sample number of the coal core in Fig.2c is not marked. In addition, is it really coal core sample? If so, the color is a little too distorted.
7. Line 130, '…experiments with wet specimens', are the 'dry specimens' missing?
8. Line 144, ’εpeak’ is inconsistent with it in line 143(εpeak)
9. The characters of the coordinate system in Figure 3a&b are not consistent. And also the font of ‘3.2’ with other title.
10. Line 206, ‘where σ1 is the total axial stress, σ1 is the total confining stress’, what exactly does σ1 stand for?
11. Line 210, ‘This suggests that pore water has a significant weakening effect on the elasticity of coal.’ Are you sure? And similarly line 405 ‘This suggests that the effect of pore pressure on the evolution of β is more significant for high porosity coal.’ It is recommended that this section be included in the discussion section.
12. Line335, Figure10 should clarify which samples were used instead of simply stating 'ZT coal samples'.
13. Line 447, 'AE analysis' should be described in' Methods'.
14. Line479, the discussion is not in-depth enough, there is no more comparison, and the reference research results are few.
15. Line 508, the conclusions should be reorganizing and simplifying.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The aim of the paper is clearly identified. The specific objectives of the manuscript are well formulated. The concept is sound and convincingly presented. The proposed methodology is credible as well as a comprehensive overview of the activities within the paper is given. The research is ambitious. The progress of the specific activities of the work beyond the state of the art and the innovation potential is sufficiently demostated. However in the results there are a figure that is limited and poorly detailed, figure 11 concerning to Mohrs circle and strength envelope of the coal sample at 9,12 and 15 Mpa confining 348 pressures: a) saturated high porosity coal samples at 3, 6 and 9 Mpa pore pressures, b) saturated 349 high porosity coal samples at 6, 9 and 12 Mpa pore pressures and c) saturated low porosity coal 350 samples at 3, 6 and 9 Mpa pore pressures. This figure should lbe improved and properly coordinated with the final conclusions.
Author Response
Thanks for your work reviewing my manuscript and helping us improve this work. Following your suggestion, we revised this manuscript carefully, and the detail is listed in the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments for author File: Comments.pdf
Author Response
Thanks for your work reviewing my manuscript and helping us improve this work. Following your suggestion, we revised this manuscript carefully, and the detail is listed in the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors revised the manuscript according to the review comments. It is suggested to check and improve some details.
1) Line 135-137. “The blue area denotes the coal matrix, the red area denotes minor porosity, and the yellow area denotes large porosity.” Please give the basis for distinguishing "small porosity" from "large porosity" in the manuscript.
2) Line 209-210. “Furthermore, under the σe3=3 MPa condition (Figure 5e), the slope of the curves decreases as σ3 and PP increase simultaneously.” The Figure should be Figure 5d, please check it.
Author Response
Thank you very much for your comments. We have made further improvements based on your comments (blue text in the revised manuscript) . Please see the attachment.
Author Response File: Author Response.pdf
