Research of Surrounding Rock Control of Gob-Side Entry Retaining Based on Deviatoric Stress Distribution Characteristics

Round 1

Reviewer 1 Report

The paper Evolution law and control of deviatoric stress in surrounding rock of retained roadway with filled concrete wall is divided into 7 chapters: Introduction, Engineering background, Strength analysis of concrete wall, Numerical simulation, Deviatoric stress and plastic zone evolution, Control mechanism and technology of roadway surrounding rock, Conclusion.  In the first chapter authors present the state of art and motivation of this paper. The second chapter describe the specific engineering case, based on real mine situated in China. The chapter 3 present the basic engineering computations which are not necessary when the numerical model will be improved. In the volume we can find mix own authors work and literature study ie. chapter 6 after presentation of own results in previous section. The paper is long and difficult to read. I have following suggestions to make these paper valuable for science:

• The title of paper is not clear. It suggest that it provide new law for analyzing the damage process in rocks. In general the word " Evolution" should be used for some phenomenon related to time. In this paper only the distribution of stresses in rocks was considered.
• I suggest to develop the numerical model, to be proper for present state of art. The numerical model should reflect more technical aspects ie. from Figure 11 and figure 12.  In general the numerical model should reflect the all mentioned aspects in the another chapters of this paper.  Authors  present high level of engineering knowledge, which can be used here. Moreover  the imperfections in rocks stratums ( likes initial cracks etc.) should be modeled. Some friction properties between stratums will be valuable. The numerical model can consider the damage of materials, it is not necessary to present the stress computed for linear material and comparison for some critical values. The finite element mesh size should be improved. I suggest not use the term " plastic" for brittle materials. This term is for ductile materials like metals. The damage of rocks are described by another models addressed for brittle or quasi-brittle materials. In the rocks the damage occur by growth of smeared cracks not by sliding of crystals.
• From the scientific point of view the analyses should concern some parametric study ie. the concrete wall thickness, or concrete properties, even the various speed of growth of fresh concrete properties in time. Authors should consider more cases.  The one analyze of specific case  is proper only for technical report.
• The conclusions have to be rewritten. I.e. The conclusion II, about rising of concrete strength is well known even for young engineers. The rest of conclusion concerning only one case, which is computed. The scientific conclusions should be more general.
• In presented form the figure 3 need to be redrawn. In the vertical axis the " P " letter is required. They are presented some simple linear relations, maybe the 3D plot is better to show the impact of Sb.
• The parameters for computing of the diagrams from Fig. 3 should be explained in the additional figure or table.
• The information about considered concrete should be written in another chapter called " material". The study should be improved for more detailed material description for numerical model. ie. the growth of modulus of elasticity per day etc.
• It seems that the chapter III is not necessary after improvement of numerical model.
• The information's presented in chapter 6 in spite of the diagrams ( fig 13. should be presented in first part of paper)

The research undertaken in this paper is very interesting, but this text should be rewritten, the numerical study greatly improved and should consider more analyses to create more general conclusions.

Author Response

Point 1: The title of paper is not clear. It suggest that it provide new law for analyzing the damage process in rocks. In general the word " Evolution" should be used for some phenomenon related to time. In this paper only the distribution of stresses in rocks was considered.

Response 1: Please provide your response for Point 1. (in red)

The title of the article was revised to " Research of surrounding rock control of gob-side entry retaining based on deviatoric stress distribution characteristics".

Point 2: I suggest to develop the numerical model, to be proper for present state of art. The numerical model should reflect more technical aspects ie. from Figure 11 and figure 12.  In general the numerical model should reflect the all mentioned aspects in the another chapters of this paper.  Authors  present high level of engineering knowledge, which can be used here. Moreover  the imperfections in rocks stratums ( likes initial cracks etc.) should be modeled. Some friction properties between stratums will be valuable. The numerical model can consider the damage of materials, it is not necessary to present the stress computed for linear material and comparison for some critical values. The finite element mesh size should be improved. I suggest not use the term " plastic" for brittle materials. This term is for ductile materials like metals. The damage of rocks are described by another models addressed for brittle or quasi-brittle materials. In the rocks the damage occur by growth of smeared cracks not by sliding of crystals.

Response 2: Please provide your response for Point 2. (in red)

In the revised version of the paper, Figure 12 and Figure 13 are changed into Figure 15 and Figure 16, and the research on the distribution law of deviatoric stress of roadway surrounding rock (Figure 12) and deviatoric stress outline line of roadway surrounding rock (Figure 13) is added, which further reflects the simulation research of roadway surrounding rock. The geological conditions of the working face are simple, the buried depth of coal seam is shallow, and there are no faults and initial large cracks. In order to facilitate the theoretical calculation of support resistance, the mechanical model is simplified and the influence of friction between rock strata is omitted. Many scholars generally use Coulomb-Mohr constitutive model in the research of simulating gob-side entry retaining with FLAC3D software, so this paper also uses Coulomb-Mohr constitutive model. In this paper, the supporting strength required for retained roadway, the growth rate of concrete compressive strength, the thickness of concrete wall and the periodic weighting step of working face are comprehensively considered, so as to obtain the reasonable thickness of concrete wall in retained roadway. The mesh size of finite element method has been reduced. The mesh size of concrete wall is 0.275m × 0.5m, that of coal is 0.5m × 0.5m, and that of roof is 0.5m × 0.33m and 0.275m × 0.33m. In this paper, "damage" is used instead of "plastic ". In the revised version of the article, the surrounding rock damage in figure 14 is re-described.

Point 3: From the scientific point of view the analyses should concern some parametric study ie. the concrete wall thickness, or concrete properties, even the various speed of growth of fresh concrete properties in time. Authors should consider more cases. The one analyze of specific case  is proper only for technical report.

Response 3: Please provide your response for Point 2. (in red)

The conclusion chapter has been revised. The research background of this paper is Hongshuliang Coal Mine, and the research results are applied in the field. The conclusions of this paper can provide reference for other similar projects.

Point 4: In presented form the figure 3 need to be redrawn. In the vertical axis the " P " letter is required. They are presented some simple linear relations, maybe the 3D plot is better to show the impact of S_b.

Response 4: Figure 3 in the initial version of the article has been changed to 3D graphics, and the picture is located in figure 4 in the new version of the article.

Point 5: The parameters for computing of the diagrams from Fig. 3 should be explained in the additional figure or table.

Response 5: The calculated data from figure 3 in the initial version of the article is added to Table 2 of the modified version of the article.

Point 6: The information about considered concrete should be written in another chapter called " material". The study should be improved for more detailed material description for numerical model. ie. the growth of modulus of elasticity per day etc.

Response 6: Chapter 3 in the revised version of the article is changed to the chapter of "materials" research. In this paper, figures 3 and 5 are added to describe the growth rate of mechanical parameters of materials. Because of the limited laboratory conditions, the mechanical parameters of the material were described by means of laboratory test and simulation. The mechanical parameters such as compressive strength, tensile strength and elastic modulus of concrete wall change with time, and with the increase of the distance from concrete wall to working face, the compressive strength of concrete wall increases continuously. Therefore, when the working face advances 2 m each time, different mechanical parameters are given to the concrete wall at different positions and different times to simulate the change trend of surrounding rock.

Point 7: The information's presented in chapter 6 in spite of the diagrams ( fig 13. should be presented in first part of paper).

Response 7 : The results of engineering practice have been put forward in the first part of the article.

Reviewer 2 Report

Dear editor,

I have reviewed the manuscript entitled “Evolution law and control of deviatoric stress in surrounding rock of retained roadway with filled concrete wall”, which investigated the distribution, evolution law of deviatoric stress, and plastic zone of surrounding rock of retained roadway under the condition of concrete filling at a coal mine in China. The idea is of interesting, and the structure and scientific discussions of the current version of the manuscript are to be improved for publication. Therefore, I as a reviewer advise a minor revision. Anyway, there are some comments which may be helpful for authors:

• It is better to change the manuscript’s title by a clear and concise subject.
• It is better to briefly mention the necessity, methodology, and findings in Abstract
• There are some spelling and grammatical errors, which dictate an in-depth review.
• It is better to mention each test was executed based on a specific standard (ASTM or ISRM or …).
• It is better to present a schematic flowchart for your methodology.
• The curves of deviatoric stresses in Fig. 8 need more explanation. It is suggested to draw a schematic section of coalface and roadways bellow each diagram.
• In numerical modeling, it is better to discuss about some issues such as mesh optimization, initial and boundary conditions, model dimensions, interface and joint properties, calibration, crack initiation and propagation, shear, compression, and tension zones, etc.
• It is better to present quantified findings in conclusion.
• I cannot find a tangible result and think the discussion section needs some improvements.

Kind regards,

Satar Mahdevari

Author Response

Point 1: It is better to change the manuscript’s title by a clear and concise subject.

Response 1: The title of the article was revised to " Research of surrounding rock control of gob-side entry retaining based on deviatoric stress distribution characteristics".

Point 2: It is better to briefly mention the necessity, methodology, and findings in Abstract.

Response 2: The problems, methods and conclusions have been explained in the abstract.

Point 3: There are some spelling and grammatical errors, which dictate an in-depth review.

Response 3: Spelling and grammar have been modified.

Point 4: It is better to mention each test was executed based on a specific standard (ASTM or ISRM or …).

Response 4: The article was revised based on specific standards. The specifications and test procedures of concrete specimens are carried out according to the standards.

Point 5: It is better to present a schematic flowchart for your methodology.

Response 5: Adding the schematic flowchart for methodology is shown in figure 7.

Point 6: The curves of deviatoric stresses in Fig. 8 need more explanation. It is suggested to draw a schematic section of coalface and roadways bellow each diagram.

Response 6: Figure 8 in the initial version of the article is changed to figure 12 and figure 13 in the modified version of the article, and the interpretation of the curve is added.

Point 7: In numerical modeling, it is better to discuss about some issues such as mesh optimization, initial and boundary conditions, model dimensions, interface and joint properties, calibration, crack initiation and propagation, shear, compression, and tension zones, etc.

Response 7: The mesh size of finite element method has been reduced. The mesh size of concrete wall is 0.275m × 0.5m, that of coal is 0.5m × 0.5m, and that of roof is 0.5m × 0.33m and 0.275m × 0.33m. The boundary and dimensions of the model are in Section 4.3. The damage of the model is explained in figure 14.

Point 8: It is better to present quantified findings in conclusion.

Response 8: The conclusion of the article has been revised.

Point 9: I cannot find a tangible result and think the discussion section needs some improvements.

Response 9: The discussion part has been improved.

Round 2

Reviewer 1 Report

The authors successfully performed the major corrections of paper. The title of paper was properly changed to reflect the real content. The abstract is seriously encourage to read all of the paper. The new organization of content makes reading easier. In the introduction the authors present the motivations for choosing the deviatoric criteria. It should be mentioned that the presence of chapter 3.1 is steel unclear. The material has a "strength" but construction has  "a load capacity". These terms should be separated. The Fig. 3 should use the same symbols like used in formulas similarly to Fig. 4. The data for computations should be mentioned in clear table. There is visible that the authors use the results from chapter 4 in chapter  5. The marking of measurments points in the Fig 15/Fig 16 will be valuable. The paper develop the interesting results of  deformation of real rocks in chapter 5. The rewritten conclusions clearly show the achieved results and impact of this paper. The volume of text was reduced to  the proper size.