Lugeon Test and Grouting Application Research Based on RQD of Grouting Sections
Round 1
Reviewer 1 Report
The paper presents an experimental study of RQD and Lugeon hydraulic tests in the Gaofeng Phosphate Mine, Hubei, China. An expression consisting in the averaging of RQD cores over geological strata is provided. Using the previous averaged RQD, fitting expressions of permeability coefficient, Lugeon permeability and grouting volumes are provided.
The reviewer thanks the authors for the manuscript, comments are given below:
1. The main concern is that the only contribution of the paper is equation (2) which is just an averaging of RQD over drill length. Fitting correlations in figures (4-7) are based on the averaged RQD proposed in equation (2). In addition, there is no validation of the proposed correlations with other data than the one used for the calibration itself.
2. There is not really an introduction but instead a summary of related works starting in line 25. The subject context needs to be introduced before related works are enumerated.
3. Why the water inflow must be less than 20m3/s?
4. In section 2.2 it is not clear why the grouting is performed, is it in the framework of an engineering application, or its sole objective is to carry the experiment object of this paper?
5. In section 5.1 how are water-cement ratios selected depending on Lugeon test results? Are the values obtained from the literature? Please explain.
Author Response
Response to Reviewer 1 Comments
Point 1: The main concern is that the only contribution of the paper is equation (2) which is just an averaging of RQD over drill length. Fitting correlations in figures (4-7) are based on the averaged RQD proposed in equation (2). In addition, there is no validation of the proposed correlations with other data than the one used for the calibration itself.
Response 1: Thanks. Jiang et al. [21] discretized the obtained RQD and permeability coefficient respectively, and derived the RQD and permeability coefficient per meter. It was found that RQD was negatively exponentially correlated with the permeability coefficient. In this paper, the average RQD and the average permeability coefficient of the grouting section are fitted, and it is found that RQDm and the average permeability coefficient are also negatively correlated. This shows that RQDm is feasible to estimate the average permeability coefficient of rock mass at different depths. Niu et al. [27] found that there was a nonlinear relationship between unit grouting volume and permeability. However, this paper finds the mean RQD has obvious symmetrical relationship with the average permeability coefficient and permeability, but does not show the size relationship. And a negative exponential correlation between the average permeability coefficient and RQDm is found. Therefore, the fitting formula of unit grouting amount and RQDm is used to obtain the grouting amount at different depths.
Point 2: There is not really an introduction but instead a summary of related works starting in line 25. The subject context needs to be introduced before related works are enumerated.
Response 2: The increase is as follows ：“Since laboratory tests on small specimens cannot predict the deformability of rock masses, in situ tests that provide direct information on deformability are necessary. However, in situ tests are expensive and time consuming. Rock Quality Designation (RQD) is one of the key parameters in rock classification [6–8]. Based on this, a large number of scholars have done extensive research on RQD”.
Point 3: Why the water inflow must be less than 20m3/h?
Response 3: According to the “Code for Construction and Acceptance of Mining Pit Engineering”, the maximum water inflow of shaft construction is less than 20m3/h.
Point 4: In section 2.2 it is not clear why the grouting is performed, is it in the framework of an engineering application, or its sole objective is to carry the experiment object of this paper?
Response 4: In shaft construction, it is crucial to use curtain grouting to reduce the permeability of the rock mass and improve the consolidation ability. By injecting cement slurry into rock fractures, artificial underground impermeable grouting curtains can be formed, cutting off waterways and creating a dry environment in mining areas.
Point 5: In section 5.1 how are water-cement ratios selected depending on Lugeon test results? Are the values obtained from the literature? Please explain.
Response 5: According to the permeability obtained by the Lugeon test [26], the appropriate slurry ratio is selected (in accordance with the relevant Chinese standard “Specification of mine curtain grouting” (DZ/T0285-2015)). The grouting water-cement ratios are designed to be 3:1, 2:1, 1:1, 0.8:1, 0.6:1, a total of five ratios. With the permeability greater than 10Lu, the cement slurry with water-cement ratio of 0.8:1 is used for grouting; with the permeability less than 10Lu, the cement slurry with the ratio of 3:1 is used for grouting.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The paper "Lugeon Test and Grouting Application Research Based on RQD of Grouting Sections" is compliant with the goal of Sustainability. The paper presents a RQD calculation methodology for grouting sections and analyzes the in-situ permeability of grouting sections by Lugeon test and permeability coefficient. I think the content is innovative and never published.
Please avoid using acronym in the title.
The abstract does not discuss the results. Add some values. "certain reference significance" is not a scientific comment.
The structure of the paper should be revised. Where is the Materials and Methods section?
Data about the case study should be moved at the end of Materials and Methods section or at the beginning of Results (it is better).
All the equations should be cited before they appear. All variables should be defined.
Not all figures are readable.
The Discussion section lacks. Can this methodology be implemented to all problems? Are there some limits? Why? When? Please explain.
The conclusion section is too short and does not present the results.
Author Response
Response to Reviewer 2 Comments
Point 1: Please avoid using acronym in the title.
Response 1: "RQDm" in the title is changed to "mean RQD".
Point 2: The abstract does not discuss the results. Add some values. "certain reference significance" is not a scientific comment.
Response 2: "certain reference significance" is deleted.
Point 3: The structure of the paper should be revised. Where is the Materials and Methods section?
Response 3: The Materials and Methods section is as follows:
5.1. Raw materials
1.Cement;
Portland cement (type PC 42.5, in accordance with the relevant Chinese standard GB175-2007) is used for the curtain grouting.
2.Water;
The grouting water complies with both the appropriate Chinese “Concrete Water Standard” (JGJ63-2006) and “Hydraulic Concrete Construction Code” (DL/T5144-2015).
3.Water reducing agent;
As the curtain grouting additive, high-performance PCA-I polycarboxylic acid with a water reducing agent parameter of 0.3% was utilized.
5.2. Grouting method
Curtain grouting is done by the grouting method of top-down, inner segmental blocking and segmental grouting.
Point 4: Data about the case study should be moved at the end of Materials and Methods section or at the beginning of Results (it is better).
Response 4: The data are shown in Table 2 to Table 4.
Point 5: All the equations should be cited before they appear. All variables should be defined.
Response 5: RQD value can be calculated by the following formula [21]:
|
(1) |
(1) |
Where, xi is the length of the ith intact core exceeding 100 mm in length, X is the total length of rock core.
Point 6: Not all figures are readable.2
Response 6: The graphics have been adjusted and the data are shown in Table 2 to Table 4.
Point 7: The Discussion section lacks. Can this methodology be implemented to all problems? Are there some limits? Why? When? Please explain.
Response 7: Discussion section is as follows:
RQDm is established on the basis of RQD, which reflects the average fragmentation degree of rock mass in long strata. Compared with RQD, the length of rock stratum calculated by RQDm is larger, and it is not accurate enough to reflect the fragmentation of specific rock stratum. Both RQD and RQDm are obtained by coring. They are susceptible to human factors during coring, and there are certain errors in measuring the length.
In grouting engineering, the prediction of grouting amount through RQDm is not applicable to all cases. It is best suited for rock strata with large cracks and large permeability. Permeability coefficient and permeability are parameters that characterize the ability of soil or rock to transmit liquid. And cement slurry particles are set with large, small permeability rocks, cement slurry is difficult to enter.
Jiang et al. [21] discretized the obtained RQD and permeability coefficient respec-tively, and derived the RQD and permeability coefficient per meter. It was found that RQD was negatively exponentially correlated with the permeability coefficient. In this paper, the average RQD and the average permeability coefficient of the grouting section are fitted, and it is found that RQDm and the average permeability coefficient are also negatively correlated. This shows that RQDm is feasible to estimate the average permeability coefficient of rock mass at different depths. Niu et al. [27] found that there was a nonlinear relationship between unit grouting volume and permeability. However, this paper finds the mean RQD has obvious symmetrical relationship with the average permeability coefficient and permeability, but does not show the size relationship. And a negative exponential correlation between the average permeability coefficient and RQDm is found. Therefore, the fitting formula of unit grouting amount and RQDm is used to obtain the grouting amount at different depths.
Point 8: The conclusion section is too short and does not present the results.
Response 8: The conclusion section changes as follows:
In addition to developed faults, folds, and irregular caverns, Gaofeng Phosphate Mine also has good water conductivity and large karst water reserves. In order to study the grouting characteristics of rock strata, within the limited parameters of this study, according to RQD and Lugeon test and curtain grouting data, the following conclusions can be drawn.
(1) It is found in this paper that RQD has nothing to do with the depth of rock strata by coring. Based on the concept of traditional RQD, proposes a method to calculate the mean RQD (RQDm) of long strata, and applies it to the calculation of RQD of grouting sections.
(2) Permeability and average permeability coefficient are obtained by Lugeon test. It is found that RQDm has a symmetrical relationship with rock mass permeability. And the average permeability coefficient has a negative exponential correlation with RQDm.
(3) By analyzing the grouting amount of curtain grouting, grouting volume is found to have a symmetrical relationship with RQDm, and the unit grouting amount is found to be negatively correlated with RQDm. According to the curve of RQD varying with depth, the grouting amount at different depths can be obtained by using the fitting formula of unit grouting amount and RQDm.
Furthermore, this method is best suited for rock strata with large fissures and high permeability. For rock mass with low permeability, clay slurry can be used for grouting, and its law needs further study.
Author Response File: Author Response.docx
Reviewer 3 Report
Lugeon Test and Grouting Application Research Based on RQD of Grouting Sections
A brief summary
The paper proposes a method for calculating the mean Rock Quality Designation (RQDm) of long stratum, which is applied to the calculation of RQD of grouting sections. Through Lugeon test and grouting test on the grouting sections, RQDm of the grouting sections is found to be directly related to the average permeability coefficient, permeability and unit grouting amount of rock mass.
Comments
1. The idea of the research is interesting and presents enough novelty.
2. The paper should attract an audience in the field of geotechnical survey and Deep Mining Engineering.
3. The paper fits the topics of the journal.
4. The proposed method seems to be innovative and contains well-known hints of originality.
Weakness of the paper:
1) Authors should anticipate some results in the abstract to capture the readers’ curiosity.
2) The results of the paper should be better highlighted.
3) The paper should be revised paying attention to the position of the figures.
4) Briefly summarize in the conclusions (using at least one sentence) the research work proposed in the manuscript.
5) The most possible future development of the proposed research should also be reported in the Conclusion
6) Use the same scales in the diagrams to allow readers to compare results.
7) The bibliography is too directed towards authors of Chinese nationality. Not that this is an absolute problem, but the contribution of previous knowledge to the research presented should be balanced
8) … no more weaknesses!
The overall merit of presented research works and findings can be taken into consideration for publishing after incorporating the above suggestions.
Author Response
Response to Reviewer 3 Comments
Point 1: Authors should anticipate some results in the abstract to capture the readers’ curiosity.
Response 1: The abstract section changes as follows:
Rock Quality Designation (RQD) and permeability coefficient are important reference indexes for grouting application. Based on the readily available RQD, RQD is found to have no relationship with the depth of rock stratum, and a method for calculating the mean RQD (RQDm) of long stratum is proposed, which is applied to the calculation of RQD of grouting sections. Through Lugeon test and grouting test on the grouting sections, RQDm of the grouting sections is found to be directly related to the average permeability coefficient, permeability and unit grouting amount of rock mass. It is found that RQDm has a symmetrical relationship with permeability and grouting volume as well as a negative exponential correlation with unit grouting volume and average permeability coefficient. According to the curve of RQD varying with depth, the grouting amount at different depths can be obtained by using the fitting formula of unit grouting amount and RQDm.
Point 2: The results of the paper should be better highlighted.
Response 2: The conclusion section changes as follows:
In addition to developed faults, folds, and irregular caverns, Gaofeng Phosphate Mine also has good water conductivity and large karst water reserves. In order to study the grouting characteristics of rock strata, within the limited parameters of this study, according to RQD and Lugeon test and curtain grouting data, the following conclusions can be drawn.
(1) It is found in this paper that RQD has nothing to do with the depth of rock strata by coring. Based on the concept of traditional RQD, proposes a method to calculate the mean RQD (RQDm) of long strata, and applies it to the calculation of RQD of grouting sections.
(2) Permeability and average permeability coefficient are obtained by Lugeon test. It is found that RQDm has a symmetrical relationship with rock mass permeability. And the average permeability coefficient has a negative exponential correlation with RQDm.
(3) By analyzing the grouting amount of curtain grouting, grouting volume is found to have a symmetrical relationship with RQDm, and the unit grouting amount is found to be negatively correlated with RQDm. According to the curve of RQD varying with depth, the grouting amount at different depths can be obtained by using the fitting formula of unit grouting amount and RQDm.
Furthermore, this method is best suited for rock strata with large fissures and high permeability. For rock mass with low permeability, clay slurry can be used for grouting, and its law needs further study.
Point 3: The paper should be revised paying attention to the position of the figures.
Response 3: The figures have been carefully examined.
Point 4: Briefly summarize in the conclusions (using at least one sentence) the research work proposed in the manuscript.
Response 4: In addition to developed faults, folds, and irregular caverns, Gaofeng Phosphate Mine also has good water conductivity and large karst water reserves. In order to study the grouting characteristics of rock strata, within the limited parameters of this study, according to RQD and Lugeon test and curtain grouting data, the following conclusions can be drawn.
Point 5: The most possible future development of the proposed research should also be reported in the Conclusion.
Response 5: Furthermore, this method is best suited for rock strata with large fissures and high permeability. For rock mass with low permeability, clay slurry can be used for grouting, and its law needs further study.
Point 6: Use the same scales in the diagrams to allow readers to compare results.
Response 6: The chart has been adjusted to the same proportion.
Point 7: The bibliography is too directed towards authors of Chinese nationality. Not that this is an absolute problem, but the contribution of previous knowledge to the research presented should be balanced.
Response 7: Multiple Chinese authors have been added as follows:
Chen, M.; Zang, C. W.; Ding, Z. W.; Zhou, G. L.; Jiang, B. Y.; Zhang, G. C.; Zhang, C. P. Effects of confining pressure on deformation failure behavior of jointed rock. J. Cent. South. Univ. 2022, 29(4), 1305-1319. https://doi.org/10.1007/s11771-022-4991-z
Chen, M.; Yang, S. Q.; Ranjith, P. G.; Zhang, Y. C. Cracking behavior of rock containing non-persistent joints with various joints inclinations. Theor. Appl. Fract. Mec. 2020, 109, 102701. https://doi.org/10.1016/j.tafmec.2020.102701
Tang, J. Z.; Yang, S. Q.; Elsworth, D.; Tao, Y. Three-Dimensional Numerical Modeling of Grain-Scale Mechanical Behavior of Sandstone Containing an Inclined Rough Joint. Rock. Mech. Rock. Eng. 2021, 54, 905–919.https://doi.org/10.1007/s00603-020-02281-2
Tang, J. Z.; Yang, S. Q.; Zhao, Y. L.; Tian, W. L. Experimental and numerical modeling of the shear behavior of filled rough joints. Comput. Geotech. 2020, 121, 103479. https://doi.org/10.1016/j.compgeo.2020.103479
Jiang, X. W; Wan, L.; Wang, X. S.; Wu, X.; Zhang, X. Estimation of rock mass deformation modulus using variations in trans-missivity and RQD with depth. Int. J. Rock. Mech. Min. 2009, 46(8): 1370-1377. https://doi.org/10.1016/j.ijrmms.2009.05.004
Niu, J. D.; Wang B.; Chen, G. J.; Chen, K. Predicting of the unit grouting quantity in karst curtain grouting by the water per-meability of rock strata. Appl. Sci. 2019, 9(22): 4814. https://doi.org/10.3390/app9224814
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Remarks 1, 2 and 4 remain unaddressed.
New comments:
Several Chinese author references have been added in the revised version. The original submission was already heavily biased towards Chinese bibliography entries, a more international bibliography would be desirable.
Reviewer 2 Report
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