Experimental Study of Mechanical Properties and Fracture Characteristics of Conglomerates Based on Mohr–Coulomb Criteria

Round 1

Reviewer 1 Report

Abstract should be more compact - less developed. Short, concise and to the point. Please limit it.

Please correct the citations in the paper - the citation is glued to the text that precedes it - there is usually no space between tinning and the text that precedes it. Please check all your manuscript in this respect and correct it.

In relation to the research material, please do not use the word "sample" - the preferred word is "specimen". Please correct all in paper.

Showing a specimen in Figure 1, please add dimensions to the figure, systematize the fonts in the figures - they should be the same, please add a description in the label of figure, which is shown in the figures marked (a), (b), (c) and ( d) and (e). Please check the entire paper in this regard. Please expand the label of figures - for each figure, please provide in the description what is on fragments (a), (b), (c), etc.

Where does the data in the graph in Figure 1c come from?

What do the colored parts of the ellipses mean in Figure 1e? What the following symbols mean - this must be explained here, not in the nomenclature at the end of the paper.

In the paper, the principal stresses sigma_1 and sigma_3 are written with Greek with a subscript in the nomeclature there are no subscripts. Please check this and check the spelling of subscripts and superscripts throughout the manuscript. It has to be systematized.

I insist that after each formula, despite the nomenclature, the quantities used in them should be explained - please correct your paper and check it.

Please systematize the notation of formulas and their position in the manuscript - font size, type, etc. Numbering of formulas should be equal to the right - centered formulas.

Please check the numbering of the paragraphs - there are errors - e.g. "2.33. D numerical model of conglomerate” – what does “2.33” and “D” mean here?

It should not be written "Fig.3(a)" but "Fig. 3a” – no spaces, unnecessary brackets. Please check the entire paper and correct the text of the manuscript.

Some pictures are blurry, please work on their resolution.

The description of the numerical model lacks its details. Please expand this section, provide a detailed description of the solver, provide a figure of the specimen with applied boundary conditions, load, fastening, write what finite elements were used in modeling, how many nodes and numerical integration points were in the element, what was the type of interpolation in the element, how many finite elements in the entire model, how many nodes were in the entire model, what was the size of the finite elements. What determined the choice of the solver and the particular division of the specimen - its discretization? How the convergence of the numerical model was assessed. Please provide detailed information about the material assumed in the numerical model. This is not in the paper - this section should be expanded and should show the authors kitchen - how they got the results.

The graphs in Figure 5 should be larger, there is no description of what is in the following parts - unclear legend. Please correct them. Same with other graphics.

Figure 13 should be of better quality and should be much larger.

The manuscript has potential - but there are some shortcomings. Please correct the paper and resubmit for review.

Minor editing of English language required.

Author Response

Response to Reviewer 1 Comments

 

Point 1：Abstract should be more compact - less developed. Short, concise and to the point. Please limit it.

 

Response 1: This is the revised summary.

“Gravel is one of the main factors affecting the mechanical properties of conglomerate, which plays a decisive role in crack propagation. In this paper, taking the conglomerate of the Baikouquan Formation in Mahu Sag of Xinjiang as the research object, a three-dimensional model of conglomerate is constructed by the discrete element numerical simulation method, and the triaxial compression experiment under different confining pressures is simulated. The mechanical properties and fracture morphology of conglomerate are analyzed with gravel content as a variable and verified by laboratory tests. In this simulation, with the increase of gravel content, the compressive strength of conglomerate decreases, the Angle of internal friction decreases, and the fractures show different forms. The results show that the gravel morphology, spatial location, and gravel content have an impact on the mechanical properties of conglomerate. The gravel content affects the formation process of the dominant fracture surface by controlling the distance between gravels so as to control the internal friction angle and it is the main controlling factor for the mechanical properties of conglomerate. Gravel cracks initiate at the edge of gravels. Stress controls the formation of main cracks under low gravel content, and the influence of gravels under high gravel content makes cracks more discrete and complex.”

 

Point 2：Please correct the citations in the paper - the citation is glued to the text that precedes it - there is usually no space between tinning and the text that precedes it. Please check all your manuscript in this respect and correct it.

 

Response 2: Have been modified.

 

Point 3：In relation to the research material, please do not use the word "specimen" - the preferred word is "specimen". Please correct all in paper.

Response 3: Have been modified.

 

 

Point 4： Showing a specimen in Figure 1, please add dimensions to the figure, systematize the fonts in the figures - they should be the same, please add a description in the label of figure, which is shown in the figures marked (a), (b), (c) and ( d) and (e). Please check the entire paper in this regard. Please expand the label of figures - for each figure, please provide in the description what is on fragments (a), (b), (c), etc.

 

Response 4: Have been modified.

 

Point 5：Where does the data in the graph in Figure 1c come from?

 

Response 5: The stress-strain curves shown in Figure 1(c) can be obtained by uniaxial and triaxial compression experiments on the conglomerate specimens.

Point 6：What do the colored parts of the ellipses mean in Figure 1e? What the following symbols mean - this must be explained here, not in the nomenclature at the end of the paper.

 

Response 6: Colors have no meaning. Pictures have been modified.

 

Point7：In the paper, the principal stresses sigma_1 and sigma_3 are written with Greek with a subscript in the nomeclature there are no subscripts. Please check this and check the spelling of subscripts and superscripts throughout the manuscript. It has to be systematized.

 

Response 7: Have been modified.

 

Point 8：I insist that after each formula, despite the nomenclature, the quantities used in them should be explained - please correct your paper and check it.

 

Response 8: Have been modified.

 

Point 9：Please systematize the notation of formulas and their position in the manuscript - font size, type, etc. Numbering of formulas should be equal to the right - centered formulas.

 

Response 9: Have been modified.

 

Point 10：Please check the numbering of the paragraphs - there are errors - e.g. "2.33. D numerical model of conglomerate” – what does “2.33” and “D” mean here?

 

Response 10: Have been modified.

“2.3 3D numerical model of conglomerate”

 

Point 11：It should not be written "Fig.3(a)" but "Fig. 3a” – no spaces, unnecessary brackets. Please check the entire paper and correct the text of the manuscript.

 

Response 11: Have been modified.

 

Point 12：Some pictures are blurry, please work on their resolution.

 

Response 12: Have been modified.

 

Point 13：The description of the numerical model lacks its details. Please expand this section, provide a detailed description of the solver, provide a figure of the specimen with applied boundary conditions, load, fastening, write what finite elements were used in modeling, how many nodes and numerical integration points were in the element, what was the type of interpolation in the element, how many finite elements in the entire model, how many nodes were in the entire model, what was the size of the finite elements. What determined the choice of the solver and the particular division of the specimen - its discretization? How the convergence of the numerical model was assessed. Please provide detailed information about the material assumed in the numerical model. This is not in the paper - this section should be expanded and should show the authors kitchen - how they got the results.

 

Response 13: We have provided detailed information about the material assumed in the numerical model in section 2.3.

 

Point 14：The graphs in Figure 5 should be larger, there is no description of what is in the following parts - unclear legend. Please correct them. Same with other graphics.

 

Response 14: Have been modified.

 

Point 15：Figure 13 should be of better quality and should be much larger.

 

Response 15: Have been modified.

 

Reviewer 2 Report

 

Title: “Experimental study of mechanical properties and fracture characteristics of conglomerates based on Mohr–coulomb criteria”

 

In this paper, the three-dimensional model of conglomerate is constructed by the discrete element numerical simulation method. The triaxial compression experiment of conglomerates under different confining pressures is simulated. The mechanical properties and fracture morphology of conglomerate are analyzed with gravel content as a variable and verified by laboratory tests. The numerical simulation results show that with the increased gravel content, the compressive strength of conglomerate decreases and the internal friction angle decreases. With the change in gravel content, conglomerate cracks show different forms. The results show that the gravel morphology, spatial location, and gravel content have an impact on the mechanical properties of conglomerate. The gravel content affects the formation process of the dominant fracture surface by controlling the distance between gravels so as to control the internal friction angle and it is the main controlling factor for the mechanical properties of conglomerate. Gravel cracks initiate at the edge of gravels. Stress controls the formation of main cracks under low gravel content, and the influence of gravels under high gravel content makes cracks more discrete and complex.

 

General comment: Although the aim of this work is interesting, this manuscript should be revised to enhance its quality and impact. In particular, the following major points should be revised.

 

2. Experimental methods and numerical models

 

1) This section should be improved. In particular, each equation used in this sections should be controlled and corrected (Eqs (1)….(7))

 

Lines: “Figure 2. Particle action diagram for linear parallel bond model “

*) This part should be improved and the diagram explained in all details

 

lines: “Figure 4. Numerical model of conglomerate”

*) This caption should be improved as well as the part of the main text describing this models

 

*) The Results section should be improved in particular “Figure 7. Gravel edge stress diagram” and the corresponding part in the main text should be reworked and improved

 

*) Eqs 8-13 should be moved in the “Methods” section

the language could be improved

Author Response

Response to Reviewer 2 Comments

 

Point 1： This section should be improved. In particular, each equation used in this sections should be controlled and corrected (Eqs (1)….(7)).

 

Response 1： Have been modified.

 

Point 2： Lines: “Figure 2. Particle action diagram for linear parallel bond model”. This part should be improved and the diagram explained in all details

 

Response 2： We have explained diagram in more details in section 2.2.

 

Point 3： lines: “Figure 4. Numerical model of conglomerate”.This caption should be improved as well as the part of the main text describing this models.

 

Response 3： We have changed the figure 4 and provided detailed information about the material assumed in the numerical model.

 

Point 4： The Results section should be improved in particular “Figure 7. Gravel edge stress diagram” and the corresponding part in the main text should be reworked and improved.

 

Response 4： We reformulated the results of Figure 7 in section 3.2.1.

 

Point 5： Eqs 8-13 should be moved in the “Methods” section

 

Response 5： Have been modified.

 

Reviewer 3 Report

In this manuscript, the authors present the effect of gravel content and shape on the mechanical properties and fracture characteristics of conglomerate, based on numerical simulations of mechanical experiments conducted on conglomerate under varying condition. The mathematical model is explained in detail. The manuscript is well written and structured. Some comparisons of the results with experimental studies are presented. However, the reviewer thinks that the following points must be addressed before proceeding further:

·         The originality of the method used in this paper should be stated more clearly. It is suggested that the writing of the abstract should be revised highlighting the novelties.

·         It is suggested to add more in-depth explanation of the model, its justification and more ‎discussions on the results.‎

·         The limitations of this work are not clearly presented.

·        Although the manuscript is written in an acceptable manner, there are still quite a few grammatical errors through the text. Please carefully proofread it again. 

• Some typo/grammatical mistakes are in the text that should be revised.

Author Response

Response to Reviewer 3 Comments

 

Point 1： The originality of the method used in this paper should be stated more clearly. It is suggested that the writing of the abstract should be revised highlighting the novelties.

 

Response 1： We have revised the abstract.

 

Point 2： It is suggested to add more in-depth explanation of the model, its justification and more ‎discussions on the results.‎

 

Response 2： We have explained the model in more details in section 2.2.

 

Point 3： The limitations of this work are not clearly presented.

 

Response 3： We have presented the limitation of this work in section 3.2.1.

 

Point 4： Although the manuscript is written in an acceptable manner, there are still quite a few grammatical errors through the text. Please carefully proofread it again.

 

Response 4： Have been modified.

 

Round 2

Reviewer 1 Report

The authors included all my suggestions in the revised version of the paper. I recommend the manuscript for publication.

 

Minor editing of English language required

Author Response

Thank you very much!

Reviewer 2 Report

 

Title: “Experimental study of mechanical properties and fracture characteristics of conglomerates based on Mohr–coulomb criteria”

 

In this paper, the three-dimensional model of conglomerate is constructed by the discrete element numerical simulation method. The triaxial compression experiment of conglomerates under different confining pressures is simulated. The mechanical properties and fracture morphology of conglomerate are analyzed with gravel content as a variable and verified by laboratory tests. The numerical simulation results show that with the increased gravel content, the compressive strength of conglomerate decreases and the internal friction angle decreases. With the change in gravel content, conglomerate cracks show different forms. The results show that the gravel morphology, spatial location, and gravel content have an impact on the mechanical properties of conglomerate. The gravel content affects the formation process of the dominant fracture surface by controlling the distance between gravels so as to control the internal friction angle and it is the main controlling factor for the mechanical properties of conglomerate. Gravel cracks initiate at the edge of gravels. Stress controls the formation of main cracks under low gravel content, and the influence of gravels under high gravel content makes cracks more discrete and complex.

 

General comment: Although the authors partially revised their work some issues should be reworked.

In particular,

 

Figure 2. Particle action diagram for linear parallel bond model.
Should be reworked together with its captions and labels. Please check the quality of the labels.

 

Figure 3. Electron microscope scan of conglomerate
*) This figure should be reworked. In particular, the current quality of images should be enhanced and the captions should be improved. It is not clear what is the meaning of subfigures b and d. Please rework.

 

Figure 4. Numerical model of conglomerate and different shapes of gravels
*) This caption should be improved.

 

Figure 5. Stress-strain curve of conglomerate physical experiment.
*) Subfigures b and d are not clear.

*) Figure 6 and 7

The captions of these figures should be improved.

Figure 9. Numerical simulation of 2D crack image and 3D crack image
Figure 10. Stress-strain curve under different confining pressure.

Figure 13.

*) See the previous comments: please rework.

The language can be further improved.

Author Response

Response to Reviewer 2 Comments

 

Point 1： Figure 2. Particle action diagram for linear parallel bond model.

Should be reworked together with its captions and labels. Please check the quality of the labels.

 

Response 1： Have changed the captions of Figure 2 as “Rheological components(a and b) and behavior(c and d) of the linear model and linear parallel bond model.”

 

Point 2： Figure 3. Electron microscope scan of conglomerate

*) This figure should be reworked. In particular, the current quality of images should be enhanced and the captions should be improved. It is not clear what is the meaning of subfigures b and d. Please rework.

 

Response 2： The quality of Figure 3 is already the highest. Have changed the captions of Figure 3 as “Electron microscope scan of conglomerate(a and c) and its corresponding elemental analysis(b and d).”

 

Point 3： Figure 4. Numerical model of conglomerate and different shapes of gravels

*) This caption should be improved.

 

Response 3：Have changed the captions of Figure 4 as “The conglomerate specimen(a) and numerical model of conglomerates (f) and different shapes of conglomerates(c,d,e). .”

 

Point 4： Figure 5. Stress-strain curve of conglomerate physical experiment.

*) Subfigures b and d are not clear.

 

Response 4：Have changed the captions of Figure 5 as “(a) Stress-strain curves of uniaxial compression physical experiments on conglomerates; (b) Relationship between gravel content and UCS; (c) Stress-strain curves of conglomerate triaxial compression physical experiments; (d) Mohr stress circle..”

 

Point 5：*) Figure 6 and 7

The captions of these figures should be improved.

Response 5：Have changed the captions of Figure 6 as. “ Physical experimental fractures under microscope(a and b) and CT scan(c and d) in conglomer-ate.”

Have changed the captions of Figure 7 as. “ Gravel edge stress diagram with chain gravel (a), block gravel(b) and spherical gravel(c).”

 

 

Point 6：Figure 9. Numerical simulation of 2D crack image and 3D crack image

Response 6：Have changed the captions of Figure 9 as. “ Numerical simulation of 2D crack image(a,b,c,d) and 3D crack image(e,f,g,h).”

 

Point7：Figure 10. Stress-strain curve under different confining pressure.

Response 7：Have changed the captions of Figure 10 as. “Stress-strain curves for different gravel contents under different confining pressures. ”

 

Point 8：Figure 13.

Response 8：Have changed the captions of Figure 5 as. “ Fracture rosette diagram for different gravel contents.”