Round 1

Reviewer 1 Report

The paper presents an approach of blast-induced vibrations for the demolition of former dam structures. For this, the authors applied several well known knowledge applied in blast-induced ground vibrations usually applied in rock mass excavation.

The case study is interesting and it can have technical value for further application in similar cases and it is very suitable for publication in a congress in the field. However, as it is, I strongly believe that this paper does not offer much novelty in what concerns to scientific knowledge.

Despite my opinion, I would like to address to the Authors some comments and opinions to improve the work.

INTRODUCTION

I completely understand and agree with the use of studied based on blast-induced ground vibrations in excavations. However, I believe that some misunderstanding can occur when the Authors make some comparisons, especially when we are comparing vibrations propagation in concrete (or man-made propagation media) and rock masses (natural propagation media). An example is when the authors claim (Introduction) that "it is crucial to accurately design blasting parameters considering all blasting disasters are directly associated with blast design". For rock mass excavation this is not completely true because in this context, two types of parameters can be  considered: the controlled parameters and the uncontrolled parameters. The first ones are those related with blast parameters (number of blast drills, spacing, burden, drill length, amount of explosive per delay, delays, etc,). The uncontrolled ones, are all related with the rock mass (discontinuities, anisotropies, etc,) and are, most of the times, the greater reasons for accidents (e.g., fly rock or damages due to resultant high vibration amplitudes).

In line 38 and 39, the sentence is not clear and should be rewritten.

According to Qiu et al (2018), in terms of ground vibration production, short delay blasts offers lower levels at distance. As a matter of fact this is true and one of the reasons are associated with frequency and frequency spectrum filtering in stress wave propagation through geological media. However, there is an important aspect referred on Qiu et al. paper with is related with the type of detonators. This should work for high precision detonation (like the electronic ones) due to the lower probability of simultaneous blast between two or more drills.

On line 64, Navarro et al reference [16 - 18] is wrong.

The description of the objectives of this work are incomplete and do not correspond to what is mentioned on conclusions.

ENGINEERING BACKGROUND

On figure 1, a) and b) should be described in figure's caption.

MONITORING VIBRATION

In paragraph that initiates in line 145, the authors present some values for vibration levels in several blasted areas. Are those maximum values?

In line 153, it is said that Figure 7 presents the PPV's in 3 directions. However I think that this figure presents the time history, not only the PPV's.

In Table 1, Authors should consider the presentation of the monitored events as a function of the detonated region and the correspondent blast type (surface or underwater).

In Equation 1 it is presented the so-called Sadovky's empirical formula. In rock blast context this formula is also known as the Ambraseys & Hendron (1968) formula. I believe that this worth mention.

DISCUSSIONS

The way that Authors present the proof for problem formulation is a bit confusing. But I believe that if some care is taken in readability (English revision), this should be easily overcome. However, there is one particular aspect that the Authors should take special attention and this is related with the assumption of a null transmitted wave in a solid/air interface. In the context of solid damage, I agree that most part of the incident wave is reflected due to large impedance difference between both media. However, the transmitted wave in the air results in important compressional waves (felt as noise) that usually cannot be neglected in terms of environmental impact.

In what concerns to Figure 10, I believe that these results need more discussion, specially ion what concerns to the prediction of lower explosive amounts per delay for higher distances, compared to lower distances.

CONCLUSIONS

In my opinion, conclusions are incomplete, considering the aim of the work, stated in chapter one. 

 

Author Response

Dear Reviewer,

We are truly grateful to your comments on our manuscript (applsci-883451 ). Based on your suggestions, we have made careful modifications on the original manuscript. All changes are marked in red color in the revised manuscript. In addition, we have consulted native English speakers for paper revision before the submission this time. We hope the new manuscript will move you.

Best wishes.

Yuanjun Ma.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript describes research on blasting of cofferdam. Upper part of blasting area was above water, and lower underwater. The authors tried to calculate charge weight per delay limit for underwater blast based on measurements from blasting monitoring data from above water blasts. The subject is not new, and manuscript does not give any new contribution to current knowledge.

Following general flaws were noticed:

• The manuscript does not present good hypothesis.
• English language need rework
• Several sentences are unclear
• Many references are not really connected to manuscript concept
• The manuscript consists several statements with no grounds

By going in more details:

• Authors are not using common terms in blasting or vibration monitoring
• Authors should explain the control influence of blasting with blasthole diameter
• Air-deck is a blasting method which is not described in this manuscript, I believe that Authors were thinking about deck loading of explosive in blasthole
• There are no technical specifications of explosive
• The blasthole loading system is unclear – how did Authors separate explosive decks, and fixed explosives at certain place. It is not clear in which manner were all explosives connected within blasthole
• Schematics of horizontal presplit blasting is unclear
• There are no 9ms, 17ms and 42ms high precision nonel detonators, only surface connectors
• As per table 1 there are 3 recordings per blast, while in figure 2 there are 9 measurement points
• PVS components are: longitudinal, transversal and vertical
• On PPV/SD diagram, there should be only 1 fitting curve
• Throughout the manuscript authors should use same markings for blasting areas
• Figure 10 and table 3
  • it is not possible that charge weight per delay decrease with increase of distance
  • it is written that maximum charge weight per delay are values 61kg and 27kg (they are minimum)
• Figure 13 should be explained in Discussion, not in Conclusions

Author Response

Dear Reviewer,

We are truly grateful to your comments on our manuscript (applsci-883451 ). Based on your suggestions, we have made careful modifications on the original manuscript. All changes are marked in red color in the revised manuscript. In addition, we have consulted native English speakers for paper revision before the submission this time. We hope the new manuscript will move you.

Best wishes.

Yuanjun Ma.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The Authors addressed all my previous comments.

Author Response

Once again, thank you very much for your comments and suggestions.

Reviewer 2 Report

The manuscript describes research on blasting of cofferdam. Upper part of blasting area was above water, and lower underwater. The authors tried to calculate charge weight per delay limit for underwater blast based on measurements from blasting monitoring data from above water blasts. The subject is not new, and manuscript does not give any new contribution to current knowledge.

The Authors made some changes in the manuscript. However even the reviewer’s comments they responded to, some of them were not included/explained in the manuscript as well. About half of the comments were not addressed to by the Authors (details below).

Following general flaws were noticed:

• The manuscript does not present good hypothesis. What did authors really do (mayor point of research) and why is it better than other approaches.
• English language still need some rework
• Several sentences are unclear
• Many references are not really connected to manuscript concept

The points that Authors did not respond to or made change in the manuscript:

• Authors are not using common terms in blasting or vibration monitoring
• Authors should explain the control influence of blasting with blasthole diameter
• Air-deck is a blasting method which is not described in this manuscript, I believe that Authors were thinking about deck loading of explosive in blasthole
• There are no technical specifications of explosive
• The blasthole loading system is unclear – how did Authors separate explosive decks, and fixed explosives at certain place. It is not clear in which manner were all explosives connected within blasthole
• Schematics of horizontal presplit blasting is unclear

Figure 13 should be explained in Discussion, not in Conclusions

Author Response

Dear reviewer,

We are truly grateful to your comments on our manuscript (No. applsci-883451). Based on your suggestions, we have made careful modifications on the manuscript. All changes have been clearly highlighted using the "Track Changes" function in Microsoft Word suggested by the editor’s. You will find our point-by-point responses to your comments in the appendix.

Once again, thank you very much for your comments.

Wish you all the best!

 

Sincerely yours,

Yuanjun Ma

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

Dear Authors,

Thank you for implementing most of my comments into your manuscript and gave answers to the rest of them.

Only a few minor changes must be done:

1. The response you wrote under point 2 you should implement in Abstract and Conclusion, because this is mayor point of your research ( Describe in 1-2 sentences that research has been done during the blasting above water to predict PPV for underwater blasting of the same structure, with successful final blasting results). Authors can additionally copy last sentence in Introduction as the last sentences in Abstract and Conclusion.
2. The word “charge” (maximum charge) or “charge per delay” should be replaced with “charge weight per delay” – line: 29, 52, 58, 59, 61, 108, 166, 168, 219
3. The word “slungshot” (blasting slungshot) should be replaced with “flyrock” – line: 35
4. Line 40 – before word “PPV” insert word “that”
5. Under the 3.1 Blast design – insert sentence describing fixing the explosive within blast hole (fixing it on a wooden stick to ensure calculated spacing between explosive decks). HOWEVER, IT IS QUESTIONABE THAT ONLY ONE NONEL DETONATOR WILL START ALL EXPLOSIVE WITHIN BLAST HOLE, 0,5M IS RELATIVELY LARGE DISTANCE FOR DETONATION TRANSFER FROM ONE DECK TO ANOTHER. ARE AUTHORS SURE THAT THERE WAS NOTHING ELSE (usually detonating cord is additionally connected to all explosive decks to ensure detonation transfer between all explosive decks) – response 10

Comments for author File: Comments.docx

Author Response

Dear Reviewer,

Thanks for your positive and constructive comments and suggestion again. We have made careful modifications on the manuscript, all changes have been clearly highlighted using the "Track Changes" function in Microsoft Word. Below you will find our point-by-point responses to the your comments:

 

Comments 1: The response you wrote under point 2 you should implement in Abstract and Conclusion, because this is mayor point of your research ( Describe in 1-2 sentences that research has been done during the blasting above water to predict PPV for underwater blasting of the same structure, with successful final blasting results). Authors can additionally copy last sentence in Introduction as the last sentences in Abstract and Conclusion.

Answer 1: We have added main innovative points and copy last sentence of Introduction as the last sentences in Abstract and Conclusion. 

 

Comments 2: The word “charge” (maximum charge) or “charge per delay” should be replaced with “charge weight per delay” – line: 29, 52, 58, 59, 61, 108, 166, 168, 219

Answer 2: The word “charge” (maximum charge) or “charge per delay” have be replaced with “charge weight per delay”.

 

Comments 3: The word “slungshot” (blasting slungshot) should be replaced with “flyrock” – line: 35.

Answer 3: The word “slungshot” (blasting slungshot) have be replaced with “flyrock”.

 

Comments 4: Line 40 – before word “PPV” insert word “that”

Answer 4: The word “that” have been insert before word “PPV”.

 

Comments 5: Under the 3.1 Blast design – insert sentence describing fixing the explosive within blast hole (fixing it on a wooden stick to ensure calculated spacing between explosive decks). HOWEVER, IT IS QUESTIONABE THAT ONLY ONE NONEL DETONATOR WILL START ALL EXPLOSIVE WITHIN BLAST HOLE, 0,5M IS RELATIVELY LARGE DISTANCE FOR DETONATION TRANSFER FROM ONE DECK TO ANOTHER. ARE AUTHORS SURE THAT THERE WAS NOTHING ELSE (usually detonating cord is additionally connected to all explosive decks to ensure detonation transfer between all explosive decks) – response 10

Answer 5: The sentence have been inserted in line 130, 131-”In particular, the explosives were fixed on a bamboo slices to ensure calculated spacing between explosive decks in a blasthole”. Absolutely, the detonating cord was used to connect to all explosive decks to ensure detonation transfer between all explosive decks, and it has been inserted in line 133, 134.

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The present paper presents an interesting study on blast-induced vibrations in the scope of demolition, particularly on vibrations propagation modelling in underwater blasts. However there are some issues that should be addressed.

In the introduction the Authors refer that "blasting is an efficient (...) and easy operation" (lines 33 and 34). I strongly disagree with this statement. Blasting, either for military or civil applications is a very complex operation considering all aspects of Explosives Engineering (economical, technical and environmental issues).

Also, in line 38, in a wide context, blasting issues are associated also with other aspects besides blast design. It is a basic knowledge that blasting risks are associated with controllable (blast design parameters) and uncontrollable (propagation medium, for example) parameters.

In line 48, the work of Singh et al. shows that underground blasts produced lower ground vibration amplitudes than the open-pit blasts but for that particular case. As stated, it seems that this is a general rule of thumb, with is not true. Ground vibration propagation is a very complex phenomena that is highly dependable on the propagation medium, particularly in natural material such as soils and rocks. Also, according to this study, it was showed that electronic initiation offers environmental advantages over other types of initiation (not only pyrotecnic but non electric too). Authors should refer why this is generally accepted.

In the Introduction chapter the Authors didn't address to the non linear modelling of vibration propagation, particularly on ground vibrations propagation, available in numerous publications.

On Section 3.1 Authors should clarify the type of initiation applied, i.e., what do they mean with "Three kind of high precision detonator".

On Section 3.2 some more information about the applied monitoring system should be addressed (sensors type, amplitudes and frequency ranges, etc.). Sensor installation description should also be indicated. In the same section, on lines 152 and 153 it is stated that "Generally, PPV is related to the distance (...) and de charge per delay". This is true only if one considers the maximum charge per delay on a blast. Nevertheless, some caution should be addressed on this statement given the dependancy on propagation medium wich (in equation 1) is implicit on Distance variable. Also, why Authors considered this model instead of Johnson's (1971) or any other, more actual or even a non-linear model?

On Figure 8, the meaning of PC and RCC should be given.

On Chapter 4, Authors indicate that "Generally the main difference between underwater and land blasting is the medium of solid contact surface (...)". This is true in the point of view of vibration propagation. But there are one other very important aspect about explosive substances that cannot be applied on the presence of water.

It should be clarified that Equation 2 is only applicable for conditions of normal incidence of a stress wave.

In Line 182, I hardly understand the concept of Shock Wave Pressure as stated. Is this the detonation pressure inside an underwater blast drill hole? Actually, I believe that the Authors should clarify the presented demonstration.

Also, the use of the PPV instead of the PVS should be justified.

About the Conclusions chapter, the authors presented some statistics on the predictions of the developed model. I believe that this can be made on the  previous chapter. Some more statistics should be addressed (for example, ANOVA validation with degrees of freedom and hypothesis test). I was expecting to have some indications about advantages and disadvantages/drawbacks on the application of the developed model, particularly some references about its generalisation ability as well as further research.

Reviewer 2 Report

The manuscript describes research on blasting of cofferdam. Upper part of blasting area was above water, and lower underwater. The authors tried to calculate charge weight per delay limit for underwater blast based on measurements from blasting monitoring data from above water blasts. The subject is not new and Authors does not give any new contribution to current knowledge.

Following general flaws were noticed:

• The manuscript does not present good hypothesis.
• English language need rework
• Many references are not really connected to manuscript concept
• The manuscript contains several statements with no grounds
• Authors are not using common terms in blasting or vibration monitoring

By going in more details:

• Several sentences are unclear
• Many statements are unclear and not explained
• There are no technical specifications of explosive
• There are no type or technical specifications of blast monitoring devices (seismographs)
• Figure 2 – many parts are unreadable due to similar colours of text and background
• How can authors control influence of blasting with blasthole diameter?
• Air-deck is a blasting method which is not described in this manuscript, I believe that Authors were thinking about deck loading of explosive in blasthole
• The blasthole loading system is unclear – how did Authors separate explosive decks, and fixed explosives at certain place. It is not clear in which manner were all explosives connected within blasthole
• Schematics of horizontal presplit blasting is unclear
• There are no 9ms, 17ms and 42ms high precision nonel detonators, only surface connectors
• As per table 1 there are 3 recordings per blast, while in figure 2 there are 9 measurement points
• PVS components are: longitudinal, transversal and vertical
• On PPV/SD diagram, there should be only 1 fitting curve
• Throughout the manuscript authors should use same markings for blasting areas
• Figure 10 and table 3
  • it is not possible that charge weight per delay decrease with increase of distance
  • it is written that maximum charge weight per delay are values 61kg and 27kg (they are minimum)
• It has not been explained why Authors took this values for further calculations
• Figure 13 should be explained in Discussion, not in Conclusions