Required Plug Strength for Continuously Poured Cemented Paste Backfill in Longhole Stopes

Round 1

Reviewer 1 Report

The reviewer read this manuscript very carefully. Yes, it is a very interesting paper on cemented paste backfill. After some minor revision. The reviewer thought that this manuscript should be accepted. The comment is shown as follows: 1. “The Williams binder is a blend of 50% Portland Type I (GU) cement and 50% Type C 140 fly ash and shows relatively continuous cohesion development with cure time.” Is that the weight percentage or volume percentage? If the weight percentage, please replace “%” as “wt.%”. Also, please revised them in the whole manuscript. Very nice paper, it provided reference for strength design of underground mine.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Main Comment

Continuously poured paste backfill dramatically improves underground mining efficiency through reduced stope cycle time and simplified logistics. For longhole stopes, a backfill  “plug” is poured to a few meters above the undercut brow and must gain sufficient strength to  prevent failure through the plug when the “main” pour begins. A novel, rational engineering design  approach that determines the required plug strength is developed. The potential failure mechanism during continuous pouring is identified and the theoretical solution and its numerical validation/calibration are discussed. Four field case histories are then used, three of them involving continuous pours, to demonstrate the theoretical solution’s validity in back-analysis. These case studies are unique in the extent and quality of total stress and water pressure measurements made through out backfilling. Also, comprehensive laboratory data are available to characterize strength development during hydration in the first few days, which are critical to the back-analyses. Results indicate that continuous backfilling is feasible with reasonably attainable backfill strengths at most mines. However, mines must undertake comprehensive early strength laboratory testing, and must carry  out field measurements during the pour to ensure the placed backfill behavior is consistent with the  analysis assumptions.

The paper is well structured and informative, with updated references, but authors are encouraged to go to another phase of manuscript review to address the following issues. The manuscript should be revised to address errors in several places.  Several examples from the text follow (p - page):

(p.4)  It is necessary to add a source to describe the Figure 2.

(p.4)  It is necessary to add a source to describe the Figure 3.

(p.5)  It is necessary to add a source to describe the Figure 4.

(p.6)  It is necessary to add a source to describe the Figure 5.

 (p.6)  It is necessary to add a source to describe the Table 1.

 (p.7)  It is necessary to add a source to describe the Figure 6.

(p.9)  It is necessary to add a source to describe the Figure 7. It would be appropriate to rework Figure 7 graphically.

(p.10)  There is a mistake, figure 7 should be marked as Figure 8, it will be necessary to renumber other figures, as well as their citations in the text.

(p.10)  It is necessary to add a source to describe the Table 3.

( p.11)  It is necessary to add a source to describe the Figure 8 (9).

(p.11)  It is necessary to add a source to describe the Table 4.

 (p.12)  It is necessary to add a source to describe the Figure 9 (10).

(p.12)  It is necessary to add a source to describe the Figure 10 (11).

(p.14)  It is necessary to add a source to describe the Table 5.

 

(p.15) In conclusion, in addition to the above, I would expect an expression of opinion and perspective of the authors on the issue of the paper. Finally, the authors of the article should pay more attention to the overall writing and clarity of their article, which should support the demonstration of their findings.

In the text, reference numbers should be placed in square brackets [ ] and placed before the punctuation; for example [1], [1–3] or [1,3]. For embedded citations in the text with pagination, use both parentheses and brackets to indicate the reference number and page numbers; for example [5] (p. 10), or [6] (pp. 101–105).

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.docx