Mechanical Characteristics Analysis and Structural Optimization of Key Component of Self-Moving Temporary Support
Round 1
Reviewer 1 Report
The title of the article does not correspond to its content. The article covers computational analysis and optimization of one element of Self-moving Temporaty Support (SmTS) - top beam. Analyzes of other elements were not carried out. So the title should contain information that the subject of the analysis is top beam and not SmTS
There are content errors in the article.
The statement (lnie 693-694), that deformation at sixt order is the largest, with value of 2.04 mm is incorrect. The result of modal analysis are not absolute displacements, but relative displacements. Relative displacements are not expressed in units of length.
The natural frequencies of the top beam of SmTS depend on (1) the stiffness of the rocks which transmit reaction to the Adaptive bottom bracket mechanism and (2) the stiffness of the other SmTS components such as Column, Base and Four-bar linkage. The scheme for which the modal analysis was carried out was not presented.
In Numerical simulation of roadway wall rock based on FLAC 3D (section 3.2), the SmTS stiffness supporting the Roof Roadway is not described. The stiffness of the SmTS has an influence on the deflections (Fig. 6a) and the stresses (Figs. 7b, 8b). The stiffness of the SmTS has not been described at all.
Other comments
I do not see the need to derive the dependencies regarding the rock mass model included in chapter 3.1 (4 pages) if these dependencies are not used in the further part of the article.
Many unavailable source materials - Master's Thesis - were cited in the literature review.
Author Response
Point 1: The title of the article does not correspond to its content. The article covers computational analysis and optimization of one element of Self-moving Temporaty Support (SmTS) - top beam. Analyzes of other elements were not carried out. So the title should contain information that the subject of the analysis is top beam and not SmTS.
Response : We would like to thank the reviewer for your thoughtful review of our manuscript. We fixed the title as follows: Mechanical Characteristics Analysis and Structural Optimization of Key Component of Self-moving Temporary Support
Point 2: The statement (line 693-694), that deformation at sixth order is the largest, with value of 2.04 mm is incorrect. The result of modal analysis are not absolute displacements, but relative displacements. Relative displacements are not expressed in units of length.
Response : Thank you very much for your insightful and constructive advice. We fixed our manuscript as follows: The deformation of the main beam at the second, fourth and sixth order modes is larger, and the deformation at the sixth order is the largest, with the maximum relative displacement of 2.04. It locates in line 708-709 in the revised manuscript.
Point 3: The natural frequencies of the top beam of SmTS depend on (1) the stiffness of the rocks which transmit reaction to the Adaptive bottom bracket mechanism and (2) the stiffness of the other SmTS components such as Column, Base and Four-bar linkage. The scheme for which the modal analysis was carried out was not presented.
Response : We want to thank reviewer for constructive and insightful criticism and advice about this problem. Due to the limitation of computer computing ability, we simplified the modal analysis of the top beam, and simplified the influence of wall rock and other support components on the natural frequency of the top beam into load and boundary conditions. The material properties, mesh division, and boundary conditions of the finite element model processed before the modal analysis are the same as those of the static analysis. We have supplemented these explanations in the manuscript line 687-691 (Section 4.4.2).
Point 4: In Numerical simulation of roadway wall rock based on FLAC 3D (section 3.2), the SmTS stiffness supporting the Roof Roadway is not described. The stiffness of the SmTS has an influence on the deflections (Fig. 6a) and the stresses (Figs. 7b, 8b). The stiffness of the SmTS has not been described at all.
Response : Thank you very much for your careful review. The numerical simulation of roadway wall rock (section 3.2) is the theoretical analysis before the support design. We only carried out some theoretical calculations for the ideal tunnel model, and did not involve the specific physical model of the support in the calculation process. According to the theoretical calculation in section 3.1, we obtained the support force that the support needs to provide. During the tunnel numerical simulation, we added the support force to the lower surface of the roadway roof to simulate the support of SmTS to the roadway roof. In this process, the influence of the SmTS stiffness on the roadway roof was not considered. The manuscript draft did not explain this part clearly, and we explained it in the revised maunscript, which is seen in line 433-436.
Point 5: I do not see the need to derive the dependencies regarding the rock mass model included in chapter 3.1 (4 pages) if these dependencies are not used in the further part of the article.
Response : We want to thank reviewer for constructive and insightful criticism and advice about the above problem. Formulas 1, 2, 3, 6 and 15 are required for the calculation of roadway surrounding rock pressure (line 352-359 in 3.1), so we retain most of the formula derivation in section 3.1 and delete formulas 4, 5, 16 and 17. After deleting 4, 5, 16, 17, 6 and 15 become 4 and 13.
Point 6: Many unavailable source materials - Master's Thesis - were cited in the literature review.
Response : Thank you very much for your careful review. All the Master’s thesis can be obtained from the website https://cnki.net/, but most of them are in Chinese.
Reviewer 2 Report
Dear Editors and Authors,
The article is an interesting analytical, numerical and laboratory study on mechanical
characteristics analysis and structural optimization of self-moving temporary support.
It may be published in the journal Applied Sciences, with the authors' consideration of the comments in the pdf strongly recommended.
With regards.
Comments for author File: 
Comments.pdf
Author Response
Point 1: Figure 3: Terzaghi not Texaki.
Response : We would like to thank the reviewer for your thoughtful review of our manuscript. We fixed the title of Figure 3, which is seen in line 315.
Point 2: Line 396. Poisson's coefficient is denoted by v and not "V". This note applies to the entire article.
Response : Thank you very much for your careful review. We have fixed all the symbol using “μ”, which is seen in line 398.
Point 3: Figure 4. The model is not big why the finite elements for "medium fine sandstone" have relatively high slenderness?
Response : We want to thank reviewer for constructive and insightful criticism and advice about the finite elements. We updated the grid of the model (shown in Figure 4), and its parameters are shown in Table 3 (Line 421). On this basis, the model is solved again.
Point 4: Line 444. In what units are the displacements?
Response : Thank you very much for your careful review. In FLAC 3D, the unit of displacement is “m”. We fixed it (line 448 and 468).
Point 5: There is no description, specific characteristics of the support used and how the support was modeled. This needs to be described. Especially since the support in Chapter 4 interacts with the roof and floor in a complicated way.
Response : We want to thank reviewer for constructive and insightful criticism and advice about the description of the SmTS. Section 4 mainly analyzes the key component of the support - the main beam, which is made of 2 longitudinal and 5 transverse rectangular steel tubes. The width and height of the steel tubes are 300mm, and its thickness is 25mm. The length of the longitudinal and transverse steel tube is 4.5m and 4.1m respectively. The transverse steel tubes are uniformly distributed on the longitudinal steel tubes. The above description has been added to the manuscript, which is seen in line 634-638. Because of the unevenness of the roof, four adaptive support mechanisms (Section 4.2.2) are designed on each beam of the roof beam. Through these mechanisms, the pressure from the roof is transferred to the roof beam, so that the complex force from the roof becomes a point force on the beam. According to the actual working conditions, the force of the main beam is loaded and analyzed under six typical working conditions: uniform loading, loading at both ends, loading at both sides, lateral eccentric loading, longitudinal eccentric loading and torsional loading. The force from the floor is transferred to the longitudinal beam of the main beam through the base and column. Each longitudinal beam is supported by two columns. The force from floor is simplified as a point force evenly distributed on the longitudinal beam for loading and analysis.
Point 6: Question. As I understand it, it is assumed that the vertical load is due to gravity, and the horizontal load is determined by the Poisson's ratio. Thus, always sV>sH. Are such primary stress conditions true?
Response : Thank you very much for your careful review. If the tectonic stress of rock stratum is considered, the horizontal load may be greater than the vertical load, that is, sH>sV. But in our design, only the vertical load of newly excavated rock stratum is considered, and our design is mainly based on the vertical load.
Point 7: Chapter 4. The support girder of the support is linear. How will the uplift of the floor between the support skids be prevented?
Response : We would like to thank the reviewer for your thoughtful review of our manuscript. The support is gantry type, and the middle of the support is the working area of the roadheader. Due to the back and forth movement of the roadheader, the uplift of the floor between the support skids can be effectively prevented.
Point 8: The ability of the support is determined by the behavior (displacement) of the exposed roof and floor in the face of the wall and immediately behind the support, before the permanent support is built. In easily deformable, swelling or creeping rocks (or soils) this can be a problem.
Response : We would like to thank the reviewer for your thoughtful review of our manuscript. The SmTS designed by us is applicable to the rock stratum with high firmness coefficient, and only the rock stratum with high firmness coefficient can form a natural equilibrium arch, which is the premise for us to apply PU’s Equilibrium Arch Theory.
Point 9: I am not entirely convinced about the design of the upper support mechanism (to be thought about in later developments of the project). In my opinion, the support frame, having no transverse bond at the bottom, may have a tendency to bend under heavy loads (at the bottom from the center toward the walls).
Response : Thank you very much for your insightful and constructive advice. At present, we have only designed the upper adaptive mechanism for the rugged geological conditions of the roof, and we have not made further tests. The support we designed is a gantry frame. The middle of the support needs to accommodate the operation of the roadheader, so there can be no horizontal connection between the supports. At present, we assume that the column with enough strength is used to support the top beam, which can avoid bending of the support frame. The subsequent development will analyze and verify the parameter selection of column.
Point 10: In my opinion, the key in this design will be the behavior of the sidewall components (actuators, joints, skids), and not the frame of the roof support. It would be appropriate to write about this problem, which is known to the authors
Response : Thank you very much for your careful review. This article is about the analysis of the top beam of the support. The main issues involved are the mechanical performance analysis and structural optimization of the top beam. The sidewall components are also important parts of the support design, which is being carried out by other team of our project team.
Point 11: The numerical analyses addressed the upper frame and its stability / stiffness. However, in my opinion, the side components of the support (cylinders, joints) and casing skids are the most sensitive to potential buckling. Also, the penetration of the skids into the floor. Especially under conditions of easily deformable rock, soil, rock / soil swelling, easily creeping, thawing, or uplifting of the floor. Therefore, in my opinion, it would be important to emphasize that this casing is only for the given conditions, almost ideal.
Response : We want to thank reviewer for constructive and insightful advice. As mentioned earlier, the temporary support designed by us is applicable to the rock stratum with high rock firmness coefficient, so the skid designed by us is applicable to the current application environment, because the rock stratum around the exploitable coal mine roadway must have enough high hardness. The side components of other supports are being designed and tested by other team of the project team.
