Experimental Study of the Crack Predominance of Rock-Like Material Containing Parallel Double Fissures under Uniaxial Compression

Round 1

Reviewer 1 Report

I think the results of the experiments you performed may be of interest to the readers of the journal, however, the content of the manuscript is hard to read and there are many redundancies. Specifically, the interpretation of the results consists of a tedious description of the single experiments. You don't normalize the results (or at least not completely) in order to find general tendencies. It is imperative for the acceptance that you strip from the content the unnecessary info and focus on few concise plots and statements. 

The experiments refer to the coalescence of two initial cracks; this issue is typical of fracture mechanics (FM) and it is not strictly associated with rock discontinuities. I am concerned about the novelty of your work, in consideration of the many similar contributions you may find in FM journals. In this respect, please, your list of references must be extended. 

The derivation of Eq. 14 is crucial, you have to check the literature for similar derivations for comparison.

Minor issues:

• testing an artificial assembly of fractures is clearly useful for a better understanding of crack growth phenomena, therefore, in  the introduction, you should focus on the complexity of such phenomena with reference to previous fracture mechanics studies;
• specify if the initial cracks run all along the normal direction;
• are the displacements of Eq. 15 utilized in the following? Not clear;
• write the formula for the fracture toughness values;
• check the English; the work of a professional is required;
• check the technical terms; for example, use "non-persistent" instead of "intermittent"

Author Response

Dear professor，please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors propose experimental results on crack interactions in a mortar material. It is a very old topic of research. Please cite the following paper:

@article{BIENIAWSKI1967407,

title = "Mechanism of brittle fracture of rock: Part II—experimental studies",

journal = "International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts",

volume = "4",

number = "4",

pages = "407 - 423",

year = "1967",

issn = "0148-9062",

doi = "https://doi.org/10.1016/0148-9062(67)90031-9",

url = "http://www.sciencedirect.com/science/article/pii/0148906267900319",

author = "Z.T. Bieniawski"}

What do you mean by “a complete research system “? Is there any digital image of the crack propagation available?

Regarding the theory of fracture mechanics and the computation of stress intensity factor, please cite :

@article{IRWIN1968241,

title = "Linear fracture mechanics, fracture transition, and fracture control",

journal = "Engineering Fracture Mechanics",

volume = "1",

number = "2",

pages = "241 - 257",

year = "1968",

issn = "0013-7944",

doi = "https://doi.org/10.1016/0013-7944(68)90001-5",

url = "http://www.sciencedirect.com/science/article/pii/0013794468900015",

author = "G.R. Irwin",

abstract = "As an analysis viewpoint, fracture mechanics treats the leading edge of a crack as a line disturbance zone in a manner similar to the treatment of dislocation lines in dislocation mechanics. Linear fracture mechanics analysis is adequate for most practical applications and permits estimates of two new length factors: the approximate size of the plastic zone, 2rY, and the crack border opening displacement, δ = ℷ/σY. Studies of crack extension behaviors as a function of the stress field parameters K and ℷ, and their interpretation with the assistance of length factors, have clarified general understanding of fracture in ways which impinge strongly on various fields of investigation such as stress corrosion cracking, fatigue, brittle transition temperature, and fracture control methods. As an example, the paper discusses interpretation of the brittle-ductile transition in terms of relative plastic zone size, and allowable-load estimates which include fracture strength in a rational way. Fracture control methods which do not rely on prior fracture failure experience are needed for new structures now under consideration. Correspondingly, the need for training and experience in fracture mechanics is urgent.}

Please, cite a paper of Griffith for the “Griffith energy criterion “. 


Detailed comments:

Line 37: “The defeats“ is not appropriate here.

Line 107: Could you be more precise here? What are the mechanical properties of the mortar and which kind of rock do you think it is similar to?

Line 122. The lower case has to be used for time unit in second.

Line 184. Why the non-linearity of the curve is not due to damage? You never consider damage here. Why?

Line 196. What kind of statistics has been performed here? How did you obtained the modes in Figure 7.

Author Response

Dear professor, please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I thank the author for the good work done for the revision. Now, the manuscript is readable snd enlightening. I suggest that it be published.

Reviewer 2 Report

Thank you for the corrections.