Anisotropy and Directivity Effects on Uniaxial Compression of Carbonaceous Slate Form Jinman Mine

Round 1

Reviewer 1 Report

I dont have essential remarks, coments cocerning reviewed manuscript.

I think that the final Chapter 4. Conclusions should not necessarily be numbered.

Topics of proposed article is very interesting.

Text of the reviewed manuscript should be published in the nearest time.

Author Response

Response to editor and reviewers’ comments

Dear editor and reviewers,

I am Cheng Yun, the corresponding author of the manuscript titled Anisotropy and directivity effects on uniaxial compression of carbonaceous slate form Jinman Mine, Manuscript ID applsci-1947146.

Thank you very much for your insightful comments on this paper. According to the questions, we have considered your comments carefully and make revisions to the paper on the basis of the last revision manuscript, as follows:

Question. I don’t have essential remarks, coments cocerning reviewed manuscript. I think that the final Chapter 4. Conclusions should not necessarily be numbered?

Answer：Thank you for your valuable suggestion, and this suggestion has been adopted.

The main conclusions are as follows:

The direction of stress loading and the bedding effect have a significant impact on strain and mechanical parameters. The deformation goes through compaction, elastic, damage accumulation, and failure stages, and there are significant differences in strain paths. The weak structural plane of the bedding controls the overall deformation when it is loaded perpendicular to a weak surface structure, showing a significant plastic deformation. The rock pillar effect weakens the axial deformation under parallel loading. The mechanical properties of grey and carbonaceous slate have significant discrete features.

The variation coefficient of gray slate samples is characterized by the peak stress, expansion stress, and elastic modulus of 1.22, 1.35 and 0.69, respectively. The variation coefficient of the carbonaceous slate samples is characterized by the peak stress, expansion stress, and elastic modulus of 1.46, 1.38, and 0.71, respectively. The uniaxial compression mechanical properties of gray and cinerous slate under different loading conditions have significant and discrete characteristics. The variations of the carbonaceous samples are greater than those of the gray samples, and they show complex fracture patterns and uneven fracture patterns in macroscopic views. The discrete degree (K) is significantly related to the direction of stress loading and different types of slate structures.

The AE response intensity of slate samples is related to the loading mode and slate type. A sudden increase in the AE cumulative ring number near the peak stress indicates instability and rupture, which can be used as a precursor of rock rupture. The failure patterns and fracture characteristics are significantly related to the slate structure. Slate samples under vertical loading and parallel loading conditions are dominated by shear fracture and tensile fracture, respectively. The peak strains of gray slate and cinerous slate are less than 1.00%, resulting in brittle failure. The SEM tests indicate that slate samples under parallel loading primarily incur tensile fracture compared with slate samples under vertical loading, and the fractured section has a smaller roughness; the scattered fractures and sections are smooth without protrusions or transcrystalline cracks.

Please check it on page 17 lines 517-542 (in blue)

Other changes:

1. To improve the readability of the paper, we asked English professional professors to polish the paper. The polished certificate is shown below:

2. According to the requirements of the journal editorial department, the email address of some authors is modified to the institutional mailbox

¹ College of Civil Engineering and Architecture, Beibu Gulf University, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

² Key Laboratory of Beibu Gulf offshore Engineering Equipment and Technology, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

³ School of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China; [email protected] (Y.C.)

⁴ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; [email protected] (Z.-P.S.)

⁵ College of Electronic and Information Engineering, Beibu Gulf University, Qinzhou 535011, China; [email protected] (X.-Y.Y.)

* Correspondence: [email protected]; Tel./Fax:+86-1738-920-6265(Y.C.); [email protected]; Tel./Fax:+86-1318-608-8693 (Z.-P.S.);

I wish to express our heartfelt thanks to the reviewers once again.

Best regards,

Cheng Yun

Author Response File: Author Response.docx

Reviewer 2 Report

Overall comment:

This work presents the anisotropic mechanical characteristics of carbonaceous shale in a real mine. The work presented developed presents interesting results, however, more than an article, perhaps the authors should have considered it as a technical note or case report.

Minor suggestions below:

• Uniform decimal format throughout the text

• Figure 9: be careful with overlapping similar colors.

• Figure 24… should be Figure 14

Author Response

Response to editor and reviewers’ comments

Dear editor and reviewers,

I am Cheng Yun, the corresponding author of the manuscript titled Anisotropy and directivity effects on uniaxial compression of carbonaceous slate form Jinman Mine, Manuscript ID applsci-1947146.

Thank you very much for your insightful comments on this paper. According to the questions, we have considered your comments carefully and make revisions to the paper on the basis of the last revision manuscript, as follows:

Question 1. Minor suggestions, uniform decimal format throughout the text?

Answer 1: Thank you for your valuable suggestion, and this suggestion has been adopted. The paper format has been rearranged according to the typesetting requirements of the journal.

Question 2. Minor suggestions, Figure 9: be careful with overlapping similar colors.

Answer 2: Thank you for your valuable suggestion, and this suggestion has been adopted.

The failure mode and fracture shapes reflect the failure mechanisms directly for different loading conditions. It not only directly reflects the stress distribution during the loading process, but also indirectly reflects the effects of differences in the degree of development, mineral composition, and internal defects of the internal structure on the overall strength. In particular, for slate rock with plate-like structures in a weathered state, there are significant anisotropic characteristics in the rock interior. Its complex stress state can easily lead to floor heave and slabbing failure in roadways.

To visualize the evolution and distribution characteristics of the cracks on the slate sample surface in Fig.9, the authors used different filling colors to characterize the tensile cracks (red) and oblique shear cracks (light blue). It can be seen from Fig. 9 that the bedding structure induces the formation of oblique shear fractures with a relatively obvious degree of penetration on the surface of rock sample, while the tensile fracture has not yet penetrated the rock sample. To demonstrate the evolution law of the main crack (oblique shear cracks), the paper covers the oblique shear crack with local secondary cracks, such as unpenetrated tensile cracks.

Please reviewers consider our intentions.

Please check it on page 12 lines 387-388 (in red)

Question 3. Minor suggestions, Figure 24… should be Figure 14

Answer 3: Thank you for your valuable suggestion, and this suggestion has been adopted. Figure 24 has been modified to show Figure 14.

Please check it on page 15 line 474 (in red)

Other changes:

1. To improve the readability of the paper, we asked English professional professors to polish the paper. The polished certificate is shown below:

2. According to the requirements of the journal editorial department, the email address of some authors is modified to the institutional mailbox

¹ College of Civil Engineering and Architecture, Beibu Gulf University, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

² Key Laboratory of Beibu Gulf offshore Engineering Equipment and Technology, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

³ School of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China; [email protected] (Y.C.)

⁴ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; [email protected] (Z.-P.S.)

⁵ College of Electronic and Information Engineering, Beibu Gulf University, Qinzhou 535011, China; [email protected] (X.-Y.Y.)

* Correspondence: [email protected]; Tel./Fax:+86-1738-920-6265(Y.C.); [email protected]; Tel./Fax:+86-1318-608-8693 (Z.-P.S.);

I wish to express our heartfelt thanks to the reviewers once again.

Best regards,

Cheng Yun

Author Response File: Author Response.docx

Reviewer 3 Report

Comments for author File: Comments.pdf

Author Response

Response to editor and reviewers’ comments

Dear editor and reviewers,

I am Cheng Yun, the corresponding author of the manuscript titled Anisotropy and directivity effects on uniaxial compression of carbonaceous slate form Jinman Mine, Manuscript ID applsci-1947146.

Thank you very much for your insightful comments on this paper. According to the questions, we have considered your comments carefully and make revisions to the paper on the basis of the last revision manuscript, as follows:

Question 1. Abstract: The SEM tests indicates that slate samples subjected to parallel loading primarily show tensile fracture compared with slate samples subjected to vertical loading, with fractured sections being of lesser roughness, and scattered fractures and sections being smooth without obvious protrusions cracks.”.“indicates” to “indicate”？

Answer 1: Thank you for your valuable suggestion, and this suggestion has been adopted. The incorrect syntax "indicates" has been changed to indicate.

Please check it on page 1 line 33 (in yellow).

Question 2. Abstract: “show tensile fracture” seems wrong, needing to be rephrased？

Answer 2: Thank you for your valuable suggestion, and this suggestion has been adopted. We have made changes. The SEM tests indicate that slate samples subjected to parallel loading primarily show a tensile failure compared with slate samples subjected to vertical loading, with fractured sections being of lesser roughness, and scattered fractures and sections being smooth without obvious protrusions cracks.

Please check it on page 1 lines 32-35 (in yellow).

Question 3. First line of section 2.1, better use “sampling location” instead of “location”?

Answer 3: Thank you for your valuable suggestion, and this suggestion has been adopted. We have made changes.

Fig.1 shows the sampling location, partial slate samples, and the mineral contents of rock samples. The carbonaceous slate samples were obtained from the Jinman Mine in Lancang River Gorge in Lanping County, Yunnan Province. The sampling location was located in the secondary overturned anticline of Enqi Anticlinorium as shown in Fig.1(a). Affected by geological tectonics, carbonaceous slates in this area have been impacted by floor heave and slabbing failure. From X-ray diffractometer analysis, gray slate is composed of quartz (71%), muscovite (15%), albite (11%), graphite (3%), and cinerous slate is composed of quartz (55%), muscovite (19%), albite (15%), calcium (8%), and graphite (3%), as shown in Figs.1(c)~(d). The average dry density and average longitudinal wave velocity of slate are 2.68 g/mm³ and 6.49 km/s, respectively.

Please check it on page 3 lines 88-96 (in yellow).

Question 4. First sentence of the second paragraph of page 4: should be “can achieve constant should be “can achieve constant pressure…testing mode/function”. Also, the term “displacement loading” is no clear.

Answer 4: Thank you for your valuable suggestion, and this suggestion has been adopted. We have made changes.

The maximum loading stress of mechanical testing machine used for this study is 1100 kN, which can achieve constant pressure testing function.

Please check it on page 4 line 117 (in yellow).

Question 5. Figure 2(a) doesn’t show a clear view of the set-up applied here. Maybe a schematic or an enlarged local view would be better?

Answer 5: Thank you for your valuable suggestion, and this suggestion has been adopted. We have enlarged Fig.2(a).

(a)

(b)

(c)

Figure 2. Experimental system: (a) Experimental apparatus; (b) Stress-strain data coupling system; (c) Zeiss ZEISS-SIGMA 300 field emission SEM

Please check it on page 4 line 126 (in yellow).

Question 6. Figure 3. Isn’t ε₁ simply ε_zz? Since the coordinates are already defined, consider using ε_zz, ε_xx and ε_yy?

Answer 6: Thank you for your valuable suggestion, and this suggestion has been adopted. We have changed Fig.3 as follows:

(a)                     (b)

Figure 3. Stress loading method: (a) Vertical loading; (b) Parallel loading

Please check it on page 5 line 157 (in yellow).

Question 7. Figure 4. (a) Stage I, which should be the stage considering the imperfect part at small strain, is too large compared to the whole loading process. This seems not necessarily for me since it looks pretty smooth and in my opinion stage I should be elastic deformation stage. Stage III, in figure 4, it is hard to distinguish stage II from stage III: they have similar slope and there is no transition point.

Answer 7. Thank you for your valuable suggestion, and this suggestion has been adopted. We have changed as follows.

Figs.4-5 show the typical stress-strain curves including axial stress-strain curve (σ-ε_xx), hoop stress-strain curve (σ-ε_xx, σ-ε_yy), and volumetric stress-strain curve (σ_v-ε_v) for vertical loading and parallel loading of gray and cinerous samples. The structural deformations of horizontal rock layers were similar to vertical loading conditions, and we only tested the hoop stress - strain curve (σ-ε_yy). It is observed that the stress-strain curves for different loading conditions can be divided into the initial compaction stage (stage I), elastic deformation stage (stage Ⅱ), and damage accumulation stage (stage Ⅲ), as shown in Figs.4-5.

The initial compaction stage (stage Ⅰ) shows that the axial deformations for both vertical loading and parallel loading are similar. When the vertical stress was loaded, the slate sample was compacted by a small load due to many micropores among the weak surface structures. The vertically superimposed slate rock had a rock pillar effect during parallel loading [17]. The strength of natural slate is noticeably greater than the strength of bedding cementation. The superimposed slate rock may only undergo axial compression and an adjustment of the alignment of mineral bundles due to a small axial loading, but not show a significant compaction process similar to that due to vertical loading.

Please check it on page 7 line 197-219 (in yellow).

Question 8. Figure 6: since stress and modulus are plotted, the unit MPa can be included in the plotting.

Answer 8. Thank you for your valuable suggestion, and this suggestion has been adopted. We have changed as follows.

The above analysis shows that the uniaxial compression mechanical properties of gray slate and cinerous slate have certain discrete characteristics. The concept of variation coefficient [16] is introduced to describe the characteristics of carbonaceous slate and is defined as the ratio of the mechanical parameters of parallel bedding and vertical bedding for the same stress loading state. Based on the peak strength (σ_c), expansion strength (σ_cd), and elastic modulus (E), the variation coefficient (K) is defined by the following equation, where ‘par’ indicates that the loading stress is parallel to slate structure, and ‘var’ indicates that the loading stress is perpendicular to slate structure.

Fig.6 shows the variation coefficients of the slate samples based on the above equation. It can be seen that the variation coefficient of gray slate samples is characterized by peak stress (σ_c), expansion stress (σ_cd), and elastic modulus (E) of 1.22, 1.35, and 0.69, respectively. The variation coefficient of the carbonaceous slate samples is characterized by peak stress (σ_c), expansion stress (σ_cd), and elastic modulus of 1.46, 1.38, and 0.71, respectively. The above analysis shows that the uniaxial compression mechanical properties of gray and cinerous slate under different loading conditions have significant and discrete characteristics. The variations of carbonaceous samples are greater than those of gray samples, and they show complex fracture patterns and uneven fracture patterns in macroscopic views. The discrete degree is significantly related to the direction of stress loading and different types of slate structures.

Please check it on page 9 line 279-296 (in yellow).

Question 9. The term “precursor point” is problematic. Precursor is normally a structure or a time period where there is potentially microscopic/undetectable change while the material remains intact. Maybe “precursor onset point” is more suitable in this case.

Answer 9. Thank you for your valuable suggestion, and this suggestion has been adopted. We have changed as follows.

(a)

(b)

Figure 7. Evolution of AE cumulative ring number under vertical loading: (a) Gray samples; (b) Carbonaceous samples

(a)

(b)

Figure 8. Evolution of AE cumulative ring number under parallel loading: (a) Gray samples; (b) Carbonaceous samples

Please check it on page 10 line 322, page 12 line 365 (in yellow).

Any other changes:

1. To improve the readability of the paper, we asked English professional professors to polish the paper. The polished certificate is shown below:

2. According to the requirements of the journal editorial department, the email address of some authors is modified to the institutional mailbox

¹ College of Civil Engineering and Architecture, Beibu Gulf University, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

² Key Laboratory of Beibu Gulf offshore Engineering Equipment and Technology, Qinzhou 535011, China; [email protected] (Z.-X.Z.)

³ School of Civil Engineering, Yancheng Institute of Technology, Yancheng 224051, China; [email protected] (Y.C.)

⁴ School of Civil Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; [email protected] (Z.-P.S.)

⁵ College of Electronic and Information Engineering, Beibu Gulf University, Qinzhou 535011, China; [email protected] (X.-Y.Y.)

* Correspondence: [email protected]; Tel./Fax:+86-1738-920-6265(Y.C.); [email protected]; Tel./Fax:+86-1318-608-8693 (Z.-P.S.);

I wish to express our heartfelt thanks to the reviewers once again.

Best regards,

Cheng Yun

Author Response File: Author Response.docx