Optimizing Retention Bunkers in Copper Mines with Numerical Methods and Gradient Descent

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

P. Bortnowski et al. have conducted a study focusing on the optimization of an ore receiving bin within a retention bunker in an underground copper ore mine. Their research presents results indicating a potential reduction in abrasive wear due to the applied optimization method. The analysis and experimental outcomes provided in their study offer credible support for these findings. However, the authors have not adequately addressed the distinct advantages of their methodology in the context of existing literature on retention bunkers. Given the plethora of studies in this field, it is crucial to delineate the unique contributions and benefits of their approach. Thus, it is strongly recommended that the authors undertake a comprehensive comparative analysis. This should encompass not only the efficiency of their method but also factors such as cost, fabrication challenges, and practical feasibility in comparison to other existing studies. This would significantly enhance the study's relevance and provide a clearer understanding of its potential impact in the field.

Additionally, there are a few minor comments that warrant attention to further refine the manuscript:

1. Clarification of Terminology: It is advisable to provide a clear definition of the abbreviation "Mg" used in the study. This will ensure that all readers, regardless of their background, fully comprehend the terms and units employed in the research.

2. Inclusion of Scale Bars in Images: To enhance the clarity and scientific rigor of the visual data, it is recommended to include scale bars in all the images presented. This addition will provide a reference for the size and scale, which is crucial for a proper understanding and interpretation of the images.

3. Explanation of Discrepancies in Table 6: The primary and optimized values of the parameters F and Q, as presented in Table 6, exhibit substantial differences. To maintain the authenticity and credibility of the simulation results, a detailed explanation for these discrepancies is necessary. Clarifying these differences will aid in validating the simulation process and the conclusions drawn from it, ensuring that the research is both transparent and reproducible.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper proposes a simulation-based optimization method for an ore receiving bin in a retention bunker in an underground mine to reduce the abrasive wear of the ore flow. The optimization comprises a variation of design parameters as well as operational parameters. The underlying DEM-simulation model is validated with measurements conducted on an existing receiving bin. Several parameters with a high influence on the optimization objective were identified. The resulting optimized design and operational parameters promise a strong decrease in abrasive wear in an ore receiving bin.

The paper is overall clearly written, comprehensive, and the quality of the paper is good. However, some parts require further clarification:

Figure 1:
The description in the figure is very small and barely readable.

Chapter 3.1:
Why was the optimization divided into two steps?
Can this two-step optimization lead to a non-optimal design, since the first two parameters L and d are then predefined for the second stage?

Table 1:
How were the ranges of parameter modifications chosen?
What were the step sizes of each parameter?

Chapter 3.3:
What were the values for the parameters for stiffness and damping and were do they come from?

Chapter 3.4:
Where do the coefficients for steel and rubber come from?

Equation 4:
The minimization of v is part of the objective function (as mentioned in equation 7).
How did you solve the optimization problem of the first stage?

Equation 6:
How are the gradients of the objective function determined?

Equation 7:
The text reads in lines 260 and 216 that the "objective function is the sum of two output variables (F and v)", but in equation 7 these variables are inputs to the function f. This equation should most likely read "f(x) = F + v" instead.
Is any normalization done on the different parts of the objective function? The values for F are orders of magnitude higher than the values for v, which could potentially lead to problems when no normalization is done.

Figure 7:
The legend is very small and not readable due to the overlap with the figure.

Line 314:
The "900 Mg" seems to be a typo, it should read "870 Mg".

Chapter 4.2:
Even though it is mentioned (and true), that precise values are not exactly necessary for an optimization, the differences between simulation model and measured values should be discussed in more detail (maybe in chapter 5). The measured values range from 425 kN to 500 kN while the simulated values drop from 500 kN down to 275 kN. Why does the simulation show such a strong variation over time whereas the measured values remain relatively constant over a much larger timescale and during a much stronger decrease in the filling of the retention bunker? Could the simulation parameters be tweaked to better match the measured values?

Figure 12:
The legend is very small and not readable due to the overlap with the figure.

Chapter 5:
The mass of the bin has not been mentioned before. Is this reduction in weight resulting from the new design only?
The discussion mentions all the benefits that arise from the optimization. Are there any possible shortcomings? Could other parameters that were not considered in this work have a significant impact as well?
As mentioned before, the difference between simulation and measured values could be reconsidered here.

In my own interest:
The optimization is done for globally evaluated values for F and v. Is it possible, that a local correlation between these values and the expected abrasive wear leads to different optimization results? Regions with high particle velocity but low contact pressure might cause less wear than regions of high contact pressure and lower particle velocity. Therefore a local coupling between Force and velocity is maybe beneficial for future optimizations.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This study analyzes retention bunkers, structures within rock masses storing ore, addressing the insufficiently studied aspects of design principles and operational factors' impact, specifically frictional component wear. The research proposes an optimization method based on Discrete Element Method (DEM) simulations to reduce abrasive wear and offers guidelines for designing new receiving bins to enhance maintenance efficiency by minimizing abrasive degradation.

(1) Explain the parameter in table 1 with a figure

(2) Figure 6, what does the blue line mean?

(3) What is the particle size distribution of the discrete elements? How does it affect the results?

(4) Two related works are recommended citing’ Main frequency band of blast vibration signal based on wavelet packet transform’ and ‘An energy‐frequency parameter for earthquake ground motion intensity measure’.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The work could be interesting. Better logic link is expected. The abstract and conclusion are not well aligned.

1. More link of design and validation are expected.

2. More quantitative analysis and discussion are expected.

3. Mind logic link and comparison.

Comments on the Quality of English Language

NA

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been revised to an acceptable level.

Author Response

Thank you very much for helping us improve our article.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed the comments well. The reviewer has no more comments.

Author Response

Thank you very much for helping us improve our article.

Reviewer 4 Report

Comments and Suggestions for Authors The improvement is not good enough. The major contribution and failure mechanisms should be discussion. 

1. More relevant failure mechanisms and condition based maintenance should be cited and discussed e.g. Ferhat Çeçen, Bekir Aktaş & Ahmet Özbayrak (2023) Non-destructive triaxial vibroacoustic modal testing with a single sound transducer: a railway sleeper case study, Nondestructive Testing and Evaluation, DOI: 10.1080/10589759.2023.2273522.

2. Major contribution nad logic link for maintenance efficiency should be provided. Comments on the Quality of English Language

NA

Author Response

Dear Reviewer,

Thank you very much for your comments, which will help us improve our manuscript. Below, we provide detailed responses to comments. All changes in the manuscript text have been highlighted in orange.

The improvement is not good enough. The major contribution and failure mechanisms should be discussion. 

1. More relevant failure mechanisms and condition based maintenance should be cited and discussed e.g. Özbayrak (2023) Non-destructive triaxial vibroacoustic modal testing with a single sound transducer: a railway sleeper case study, Nondestructive Testing and Evaluation, DOI: 10.1080/10589759.2023.2273522.

The suggested article was cited, and based on it, the problem of wear under the influence of vibrations and the associated risks were defined: “Vibrations in structures can significantly impact wear, as induced oscillations can lead to increased friction between moving parts, accelerating their degradation [14]. Additionally, uneven distributions of vibrations can cause uneven loads on structural elements, resulting in locally intensified wear, highlighting the necessity of precise modal analysis in the design and maintenance process [15].”

2. Major contribution and logic link for maintenance efficiency should be provided.

In the introduction section, we have detailed our contribution and innovation more thoroughly: ”The innovation of the research results lay in the optimization of the bunker receiving bin's design using real structural loads, which had not been clearly defined until now. Based on simulation, it was proven that design changes to these unique structures allow for improvements in the bin's working conditions and potentially reduce damage.”

In our opinion, as well as in the view of the other three reviewers, the logical chain of argumentation is presented in a clear manner. The other reviews unambiguously confirmed that the issues presented constitute a significant addition to the current state of knowledge:

• We conducted a review of the scientific literature related to retention bunkers. Due to the scarcity of publications on this topic, focus was also placed on similar constructions such as conveyor belt transfer points. No studies were found that analyze the impact of structural load on the process of excessive wear like ours.

• We identified the main causes of wear (the force exerted by the accumulated ore and the velocity of ore particle movement).

• We proposed a numerical experiment that demonstrated the impact of design features on improving the wear process and allowed for the selection of an optimal operating point for one receiving bin.
• The optimization results were presented as a path to improving maintenance efficiency and extending the lifespan of the bunkers.