Numerical Study on the Dynamic Response of Gas Explosion in Uneven Coal Mine Tunnels Using CESE Reaction Dynamics Model

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This article describes an experiment in a mine and analyzesyzes the effects of some explosions.

The numerical model is well written, and at the same time, the fact that they managed to carry out this experiment is a world-renowned success.

With mining activity reduced to a minimum in Europe, writing an article on confined area explosions is difficult, mainly due to the need for test locations. That is precisely why this article is very publishable.

I would recommend (but not necessary)

a. completing the article with its numerical model to describe the results  of the effects and explosive mixtures (methane, ethane)

b. a more detailed analysis of the effects of the explosion on the employed personnel (surprisblast explosion).

Comments on the Quality of English Language

This paper is very interesting to publish in your journal.

 

Author Response

Dear Editor:

On behalf of my co authors, we greatly appreciate the opportunity to revise our manuscript, as well as the comments from the editors and reviewers on our manuscript titled "Numerical Study of Gas Explosion Dynamic Response in Uneven Coal Mine Tunnels Using LS DYNA CESE Reaction Dynamics Model" (App lsci-2903396), these suggestions are very helpful for our future research work.

Recommendation a:

Completing the article with its numerical model to describe the results  of the effects and explosive mixtures (methane, ethane)

Answer:

Due to the complex chemical reaction mechanism of methane, ethane and other gases mixed combustion, which are the main components of free gas underground in coal mines, the calculation cost is high. Therefore, we only simulated and studied the scenario of methane explosions in tunnels. In the following work, we will consider using our school's explosion experimental equipment to conduct combustion and explosion experiments on alkane mixtures. Meanwhile, we will also use Chemkin software to conduct reaction kinetics simulation analysis on the detonation of methane and ethane mixtures in closed containers.

Recommendation b:

A more detailed analysis of the effects of the explosion on the employed personnel (surprisblast explosion).

Answer:

We are currently conducting research on the injuries caused by explosions in underground tunnels. In future research, we will place the human body model into a tunnel with uneven walls to study the process of the explosion wave washing away personnel after a gas explosion and the impact of personnel obstruction on the propagation of the shock wave, as shown in Figure 1. From the simulation results (Figure 2), when the shock wave passes through the human body, the overpressure of the shock wave increases in front of and on both sides of the human body, and a similar “U”-shaped low-pressure area exists behind the human body. At the same time, the shock wave causes the human body to be washed away to a certain distance. However, some important details need to be adjusted (including the deformation of the human body, the friction between people and the tunnel wall) to achieve a comprehensive analysis, and this study needs further improvement.

Fig. 1. Numerical model for gas explosion in uneven and convex tunnels considering the workforce in the tunnel

Fig. 2. Interaction process between shock waves and obstacles

Thank you and best regards.

Sincerely,

Du Jiaqi

Chen Jian (corresponding author)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article contains interesting numerical studies that relate to the assessment of pressure and stress distribution in a real and smooth wall tunnel. The presented results are very important due to the assessment of the impact of explosive gases on the stability of underground workings. Indicating corner zones for overloads may be helpful in preventing natural hazards. Below are some comments and suggestions:

1. In the introduction, a few sentences should be added regarding research on physical models, in which the impact of mine gas explosions on the destruction of workings was determined - this will constitute the background for numerical research;

2. In the subsection 2.3, it should be written more clearly how the parameters presented in table 2 were determined/selected - whether these are your own research or rather borrowed from the literature;

3. In the third chapter regarding numerical modeling, some information should be added about: mesh density and contacts between the support materials and the rock mass;

4. In the subsection 4.2, indicate/add some information whether the unevenness in the excavation also relates to the convergence and uplift of the floor;

5. In the subsection 4.3, please write what failure criterion was used to determine the stress state and which is presented in Figure 11. In addition, please write whether the analysis took into account the influence of the strength parameters of the arch yielding support or rather the excavation was modeled without the support;

6. In the fourth chapter, reference should be made to the limit values of the excavation displacement so that the results can be compared - in other words, will the excavation lose its functionality (stability) as a result of an explosion?

7. The conclusions cover the scope of the research and are sufficient.

Author Response

Dear Editor:

On behalf of my coauthors, we greatly appreciate the opportunity to revise our manuscript, as well as the comments from editors and reviewers on our manuscript titled “Numerical study on the dynamic response of gas explosion in uneven coal mine tunnels using LS DYNA CESE reaction dynamics model” (NO.applsci-2903396).

After reading the comments provided by the editors and reviewers, we have responded to these issues in the modification instructions and revised each issue in the paper. The attachment includes modification instructions of the paper. The modified content has been marked in yellow. We hope to submit it for your consideration.

We greatly appreciate your and the reviewers’ comments on our paper. At the same time, thank you for your contribution to scientific research, which is also our lifelong goal.

Thank you and best regards.

Sincerely,

Du Jiaqi

Chen Jian (corresponding author)

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The reviewed article entitled "Numerical study on the dynamic response of gas explosion in uneven coal mine tunnels using LS DYNA CESE reaction dynamics model" raises an extremely interesting and important topic regarding the exploitation of coal deposits containing methane. This is a very interesting work dealing with an issue that is important from the point of view of the safety of underground workers and increasing the extraction of coal resources. A gas explosion is the most serious dynamic disaster in hard coal mines and often causes a large number of victims, damages the tunnel walls and causes losses of mining equipment. One of the innovations proposed by the authors is the use of gas explosion simulations combining the chemical reaction mechanism and the tunnel structure; Shock wave flow fields during gas explosions in tunnels with uneven and smooth walls were compared; Dynamic reactions in tunnels with uneven and smooth walls were analyzed. This allows predicting the behavior of the shock wave and provides an answer to what needs to be done to reduce the propagation speed and overpressure of the shock wave. The simulations performed enable quick modeling of gas explosions in various closed or semi-closed spaces. The simulations performed allow for accurate capture of the shock wave flow field at every moment. This allows us to draw the conclusion that the stress distribution in the tunnel is uneven (not continuous), which results in a shorter duration of heavy loads. Simulations have shown that the displacement of the approximate real tunnel after a gas explosion is smaller than in the case of tunnels with smooth walls, and the area of the plastic deformation zone is small. The calculated displacement of the wall of the discontinuous tunnel is at most 26.9% smaller than in the smooth tunnel. The article presents the achieved simulations (research) in a very interesting way, and the illustrations show the sequence of simulations performed. Based on the literature review, the authors directly indicated the advisability of using a simulator for such research. The result of the simulations is the determination of functions that should be met and/or taken into account when designing tunnels. The discussion conducted by the authors sets directions for further research and is an excellent starting point for indicators to be taken into account when designing tunnels. The article can be published in its current form.

Comments on the Quality of English Language

Minor English editing is required.

Author Response

Dear Editor: 
On behalf of my coauthors, we greatly appreciate the opportunity to revise our manuscript, as well as the comments from editors and reviewers on our manuscript titled “Numerical study on the dynamic response of gas explosion in uneven coal mine tunnels using LS DYNA CESE reaction dynamics model” (NO.applsci-2903396).
After reading the comments provided by the editors and reviewers,  we made revisions to the paper. The attachment includes the revised version of the paper, and the revised content has been highlighted in yellow. We would like to submit it for your consideration.
We greatly appreciate your and the reviewers’ comments on our paper. At the same time, thank you for your contribution to scientific research, which is also our lifelong goal.
Thank you and best regards.
Sincerely,
Du Jiaqi
Chen Jian (corresponding author)