An experimental study of the influence of lithology on compaction behaviour of broken waste rock in coal mine backfill

The research aims to explore the influences of lithology on the compaction behaviours of broken waste rocks. For this purpose, a WAW-1000D servo test machine and a self-made bidirectional loading test system for granular materials were used to conduct axial and lateral compaction tests on four typical types of broken waste rocks: sandstone, mudstone, limestone and shale. On this basis, we analysed the relationships between lateral and axial stress with the strain in, and porosity of, the four types of broken waste rocks. In addition, the relationship of axial stress with lateral stress and lateral pressure coefficient, and the changes in the particle size distribution of broken waste rocks before and after compaction were discussed. The test results demonstrated that the samples of higher strength were found to have low lateral and axial strains as well as a lower porosity in axial and lateral loading tests, while samples of lower strength showed low lateral stress and lateral pressure coefficient under axial load. After being compacted, the samples of the four types of broken waste rocks were found to have a higher proportion of small particles, indicating some particle crushing. Moreover, the samples of lower strength were broken to a greater extent.


Comments to the Author(s)
In this paper, a self-made bidirectional test system is used to test effects of lithology on compaction behaviors of waste rocks, which will provide the lithology selection for the backfill materials. Meanwhile, the research results will be helpful to reduce the pollutions in mine areas. The paper is interesting and is worthy of consideration for publication in the RSOS. However, many details are missing. The reviewer has some minor corrections or comments that the authors need to address to improve the quality of the paper. According to the contents of sample preparation and test scheme, the waste rock sample is not belonging to coal gangue, which kind of the waste rock is used as the samples? If this size of the loading box is enough for waste rock samples, please add the explanation. Figure 4 is not necessary. The test steps have been stated in the main text. It should be deleted. Page 6: line 23-24, after placing each layer, the rock blocks were pre-compacted until all layers were loaded. Not very clear. Please, rephrase or explain a bit better. Page 10: line 32-34, by the term lateral pressure coefficient you mean the ratio of horizontal to vertical stresses? Porosity usually represents the ratio between the volume of void and the total volume of a given material, containing also this void. On the other hand, ℎ and in Equations (4) and (7) represent something similar to the volumetric strain (−)/, which is the ratio between the variation of volume and the original volume.

18-Feb-2019
Dear Professor Zhang, The editors assigned to your paper ("An experimental study of the influences of lithology on compaction behaviours of broken waste rocks in coal mine backfilling") have now received comments from reviewers. We would like you to revise your paper in accordance with the referee and Associate Editor suggestions which can be found below (not including confidential reports to the Editor). Please note this decision does not guarantee eventual acceptance.
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Once again, thank you for submitting your manuscript to Royal Society Open Science and I look forward to receiving your revision. If you have any questions at all, please do not hesitate to get in touch.
Kind regards, Andrew Dunn Royal Society Open Science Editorial Office Royal Society Open Science openscience@royalsociety.org on behalf of Prof R. Kerry Rowe (Subject Editor) openscience@royalsociety.org Associate Editor's comments: Please revise your manuscript to fully address the reviewers' concerns. They are broadly positive about your work, but we would like you to make sure you do a good job with the revisions (both scientifically and in checking the language in case you can improve its clarity at all).
The reviewers may be asked to assess your changes, so make sure you provide a full point-bypoint response in your revision. Good luck! Comments to Author: Reviewers' Comments to Author: Reviewer: 1 Comments to the Author(s) The manuscript is easy to follow and has an appropriate structure. It is an interesting experimental study and might have applications in the coal mine environmental protection. However, there are some contents needing to be modified to improve the quality of the manuscript. Therefore, I suggest a minor revision before the manuscript could be accepted for publication. The following suggestions and comments should be considered when revising the manuscript. Specific Comments: No.1: the compaction of crushed waste rock was the main focus of this study, which is the main method to quantify the compaction process. Comments to the Author(s) In this paper, a self-made bidirectional test system is used to test effects of lithology on compaction behaviors of waste rocks, which will provide the lithology selection for the backfill materials. Meanwhile, the research results will be helpful to reduce the pollutions in mine areas. The paper is interesting and is worthy of consideration for publication in the RSOS. However, many details are missing. The reviewer has some minor corrections or comments that the authors need to address to improve the quality of the paper. According to the contents of sample preparation and test scheme, the waste rock sample is not belonging to coal gangue, which kind of the waste rock is used as the samples? If this size of the loading box is enough for waste rock samples, please add the explanation. Figure 4 is not necessary. The test steps have been stated in the main text. It should be deleted. Page 6: line 23-24, after placing each layer, the rock blocks were pre-compacted until all layers were loaded. Not very clear. Please, rephrase or explain a bit better. Page 10: line 32-34, by the term lateral pressure coefficient you mean the ratio of horizontal to vertical stresses? Porosity usually represents the ratio between the volume of void and the total volume of a given material, containing also this void. On the other hand, ℎ and in Equations (4) and (7) represent something similar to the volumetric strain (−)/, which is the ratio between the variation of volume and the original volume.

Author's Response to Decision Letter for (RSOS-182205.R0)
See Appendix A.

Do you have any ethical concerns with this paper? No
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Dear editor and reviewers,
On behalf of my co-authors, we thank you very much for giving us an opportunity to revise our manuscript. We are grateful to the editor and reviewers for their positive and constructive comments and suggestions on our manuscript entitled "An experimental study of the influence of lithology on compaction behaviour of broken waste rock in coal mine backfill" (RSOS-182205). These comments have all been of great help to us in the revision and improvement of our paper, as well as providing significant guidance for our research.
We have revised our manuscript according to the comments from the reviewers and have used a professional language editing service to improve its grammar and writing style. We hope that the manuscript now meets with your approval. The main