Experimental study on repair of fractured rock mass by microbial induction technology

The surrounding rock mass is often required to have good strength and impermeability in underground engineering. Some grouting methods, such as the chemical grouting method and the cement grouting pressure pump method, are often applied to reform underground environment and improve the engineering performance of rock mass. However, the application of some traditional grouting materials would destroy the original environment in which the project is located. This paper focuses on the repairing effect of Bacillus pasteurii composites in fractured rocks. The repairing effect of microbial materials on fractured sandstone is analysed through nuclear magnetic resonance (NMR) and unconfined compression-shearing equipment. The result shows that the longer the repairing time is, the better the effect will be. After 42 days of repairing, the porosity of fractured sandstone decreases by 36.41%, the impermeability increases by 94.62%, and the compressive strength increases by 30.52%. Through the study of reaction mechanisms, this technology has the advantages of mild reaction conditions, no pollution and good environmental compatibility. The application of this technology to the maintenance of geotechnical engineering can provide new ideas for the research and development of new environmental grouting materials and underground space reconstruction technology.


22-Oct-2019
Dear Dr Gao, On behalf of the Editors, I am pleased to inform you that your Manuscript RSOS-191318 entitled "Experimental Study on Repair of Fractured Rock Mass by Microbial Induction Technology" has been accepted for publication in Royal Society Open Science subject to minor revision in accordance with the referee suggestions. Please find the referees' comments at the end of this email.
The reviewers and handling editors have recommended publication, but also suggest some minor revisions to your manuscript. Therefore, I invite you to respond to the comments and revise your manuscript.
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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. Article deals with an important issue of repairing fractured rocks by using Bacillus pasteurii composites. The repairing effect of microbial materials on fractured sandstone is analysed by means of nuclear magnetic resonance (NMR) and unconfined compression-shearing equipment. Authors were successful in using the analytical and testing methods. However, some comments need to be rectified: 1. Introduction part needs to be extended to include other used materials for repairing stones, bricks and concrete. The following research have already discussed this topic:  Figures 5, 7 and 8. 3. In section 4 (Mechanism of MICP repairing fractured rock), please extend the discussion and explain more on the influence of calcium carbonate and its presence in the cemented sand.

Please include error bars in
4. Please make the annotation on SEM images clearer. Text in the images are barely read.
5. Manuscript needs proofreading. Some grammar mistakes were detected.
I would like to recommend this article for publication after authors rectify the previous comments. Article deals with an important issue of repairing fractured rocks by using Bacillus pasteurii composites. The repairing effect of microbial materials on fractured sandstone is analysed by means of nuclear magnetic resonance (NMR) and unconfined compression-shearing equipment. Authors were successful in using the analytical and testing methods. However, some comments need to be rectified: 1. Introduction part needs to be extended to include other used materials for repairing stones, bricks and concrete. The following research have already discussed this topic: Author's reply: We have modified the introduction and added some of the latest references.

Please include error bars in Figures 5, 7 and 8.
Author's reply: We have modified these figures, and we have added error bars in Figure  5 and Figure 7. Figure 8 shows the stress-strain curve of the test piece, which mainly reflects the peak intensity change under different conditions. This is a relatively straightforward result, so the error bars are not added. 3. In section 4 (Mechanism of MICP repairing fractured rock), please extend the discussion and explain more on the influence of calcium carbonate and its presence in the cemented sand.
Author's reply: We have supplemented this section as follows: Composition analysis before experimental processing

Composition analysis after experimental processing
From the comparative analysis of the composition of the cemented sand before and after the test, the XRD spectra of the sand mixture processed by MICP test can detect obvious peaks of calcium carbonate, which indicates that a considerable amount of calcium carbonate is produced during the test. The calcium carbonate formed by MICP has a high degree of bonding with the geotechnical material, and the depth of the bonding layer can reach the micron level. Calcium carbonate is not only a filler between the pores of the soil, but also a good cementing object. The soil particles are bonded together and a layer of calcium carbonate protective film is deposited on the surface of the rock to improve the durability of these materials. The reinforcement effect is achieved by reducing the void ratio and permeability coefficient of the soil and increasing the strength.
4. Please make the annotation on SEM images clearer. Text in the images are barely read.
Author's reply: We have re-edited the images and text in them. Author's reply: We have revised some of the contents of the manuscript based on the comments.
I would like to recommend this article for publication after authors rectify the previous comments.
Reviewer: 2 Comments to the Author(s) This research on MICP technology is detailed and meaningful. By combining the analysis of microstructure features with macroscopic performance, the authors present reliable results. Therefore, I suggest that this article be accepted for publication. 1. The contents of Table 1 need to be revised.
Author reply: Modified Table1