Study on the Influence of Subway Tunnel Induced by Under-Crossing Tunnel Based on Monitor Data in Shenzhen, China
Round 1
Reviewer 1 Report
The authors are trying to investigate the impact of an under-construction tunnel under crossing subway tunnels using monitoring data.
A first comment reading carefully the article is that the paper could be of interest to the readership of the journal. However, there are many points that should be written more clearly. I explain my points in more detail below. Thus, to make this paper publishable, the authors need to respond to the following remarks.
Minor remarks:
(1) Lines 19-21: Authors claim that the aim of the under review manuscript may provide guidelines for tunnels under crossing existing tunnels under similar conditions. Personally, reading the whole article, I could not find those guidelines.
(2) Authors use the word “mileage”. In my opinion, they should try to use another similar word. I do not think that this word is the appropriate one. In addition, my suggestion is those “mileages” (for example SK3+528) should be depicted at Fig. 1.
(3) In Fig. 2, authors should correlate the names depicted in the geological map with the ones in the description legend.
(4) Generally, there are some issues with the English language in the manuscript (in some places), meaning that some phrases are written wrongly from a syntax point of view (e.g. lines 241-243), or grammatical point of view (e.g. line 114: main regional geologic).
Major remarks:
(5) I propose that the authors should add a paragraph describing the geomechanical behaviour of each geological formation of Table 1 towards the under-construction tunnel and refer to the potential consequences that may cause during the construction phase. This description is crucial for the monitoring process and can justify many problems that can arise during the excavation. To be more specific, in Fig. 3, a variety of weak geological formations are depicted (e.g. residual soil, fully weathered mixed granite, silt, coarse sand). The geomechanical behaviour of those formations must be taken seriously into consideration during the excavation process and I think that some related remarks should be integrated into the under review manuscript.
(6) There is no written something about the potential role of groundwater regarding the measurement of monitoring data. Formations such as plain fill, coarse sand, residual soil, and weathered granite are susceptible to the infiltration of groundwater and as a result, this can affect the stability of the under-construction tunnel and its surrounding geoenvironment. In my opinion, authors should dedicate a paragraph referring to that parameter (e.g. role of groundwater) also.
(7) Judging from Fig 4a, the basic geological formation between subway line 11 and the deep tunnel, is the (fully + weakly) weathered mixed granite. I think that this remark should be highlighted in the manuscript regarding the geomechanical behaviour of the weathered mixed granite during the tunnelling process.
(8) In my opinion, what is described in Sections 3.2 & 3.3, should be furthermore justified by referring to the geological conditions as the tunnel progress is moving away respectively.
(9) It would be useful if authors give a more detailed description of the “hardware” or equipment of the monitoring system.
(10) Lines 342-349: Explain from a geological point of view why those sink values happen.
(11) Line 353-354: The safety requirements of subway tunnel are based on which accepted guidelines (or references)?
(12) Line 361: I believe that the described authors' application of on-site monitoring, is used anyway for many similar projects around the world.
(13) Should authors add more references in their article?
Last and more general comment: Regarding the last paragraph of the Introduction (lines 69-73), where the authors refer that the aim of this paper is to provide reference and support for similar projects, I do not think that this indeed happens. To me, the article is not a new suggestion to the tunnelling community since in my opinion, many similar projects are constructed using more or less that kind of monitoring system.
Moderate editing of English language required
Author Response
We thank editor and reviewers for their valuable comments on our manuscript. In the following, we respond to these comments in the order of their appearance in your email.
Comment: Authors claim that the aim of the under-review manuscript may provide guidelines for tunnels under crossing existing tunnels under similar conditions. Personally, reading the whole article, I could not find those guidelines.
Response: We have added relevant content in the manuscript.
Through these real-time monitoring data, we can know where the existing tunnels are at higher risk of deformation during the process of under tunneling, which helps to adjust the tunnelling parameters timely to ensure the existing tunnel within a safe state.
Comment: Authors use the word “mileage”. In my opinion, they should try to use another similar word. I do not think that this word is the appropriate one. In addition, my suggestion is those “mileages” (for example SK3+528) should be depicted at Fig. 1.
Response: We agree your suggestion, the expressions are modified in the manuscript.
Comment: Generally, there are some issues with the English language in the manuscript (in some places), meaning that some phrases are written wrongly from a syntax point of view (e.g., lines 241-243), or grammatical point of view (e.g. line 114: main regional geologic).
Response: We have modified these issues.
Comment: I propose that the authors should add a paragraph describing the geomechanical behaviour of each geological formation of Table 1 towards the under-construction tunnel and refer to the potential consequences that may cause during the construction phase. This description is crucial for the monitoring process and can justify many problems that can arise during the excavation. To be more specific, in Fig. 3, a variety of weak geological formations are depicted (e.g., residual soil, fully weathered mixed granite, silt, coarse sand). The geomechanical behaviour of those formations must be taken seriously into consideration during the excavation process and I think that some related remarks should be integrated into the under-review manuscript.
Response: We have made modifications to the content in Table 1 and added relevant content.
Comment: There is no written something about the potential role of groundwater regarding the measurement of monitoring data. Formations such as plain fill, coarse sand, residual soil, and weathered granite are susceptible to the infiltration of groundwater and as a result, this can affect the stability of the under-construction tunnel and its surrounding geoenvironmental. In my opinion, authors should dedicate a paragraph referring to that parameter (e.g., role of groundwater) also.
Response: Your suggestion is very good. We have added relevant content in manuscript.
Comment: It would be useful if authors give a more detailed description of the “hardware” or equipment of the monitoring system.
Response: We have added relevant content in Fig. 6.
Comment: Line 353-354: The safety requirements of subway tunnel are based on which accepted guidelines (or references)?
Response: We are based on the standard "Management Measures for Rail Transit Operation Safety Protection Zone and Construction Planning Control Zone Engineering" of Shenzhen City in 2021.
Comment: Line 361: I believe that the described authors' application of on-site monitoring, is used anyway for many similar projects around the world.
Response: We have modified it.
Comment: Should authors add more references in their article?
Response: We have added some relevant references in the manuscript.
Comment: Regarding the last paragraph of the Introduction (lines 69-73), where the authors refer that the aim of this paper is to provide reference and support for similar projects, I do not think that this indeed happens. To me, the article is not a new suggestion to the tunnelling community since in my opinion, many similar projects are constructed using more or less that kind of monitoring system.
Response: This paper is about the deformation monitoring and control method of the existing subway tunnel under a new tunnel under-crossing; On the other hand, we analyze the monitoring data and summarize the deformation rule and pattern of the existing subway tunnel. We hope that it may provide better understanding of the processes of deformation patterns and control of the existing subway tunnel induced in the preceding of subsequent new tunnel under-crossing.
Reviewer 2 Report
The introductory sentences could be more clearer. Start by explaining the significance of underground tunnels in urbanization. Mention the objective of the study more explicitly in the opening sentences. Consider rephrasing the sentence: "In this study, we mainly investigate the displacement of subway line 11 induced by the under crossing of the Qianhai-Nanshan Integrated Drainage Deep Tunnel in Shenzhen." This sentence seems incomplete and may contain typographical errors. Proofread the entire text for grammatical errors and typos. Use consistent and accurate terminology. If the terms "subsequent tunnel" and "under-crossing" have specific meanings in your context, make sure to define them clearly for the reader. Define any technical terms that might not be commonly understood by a general audience. Provide more details about the displacement monitoring data and the methods used for analysis. What techniques were employed for measurement and analysis? Were simulations or models used? Include graphs, diagrams, or charts to visualize the displacement process and its impact on subway line 11. Be specific about the results obtained from the analysis. What were the key findings related to subway line 11's displacement? How significant was the impact? Offer a more comprehensive discussion of the implications of the results. How can this information be practically applied to minimize disruption and ensure safety during subsequent tunnel construction? Expand on how the "displacement detection" measures could be practically implemented to control the impact of subsequent tunnel under-crossings. Provide examples or recommendations for construction planning and execution. Specify the conditions under which the findings and guidelines are applicable. Are there specific types of tunnels, geological conditions, or urban settings for which these guidelines are most relevant? Include additional references that are relevant to related studies, research, or projects that support your findings or provide context for your work. Ensure a consistent and clear writing style throughout the document. Avoid using overly complex sentence structures that might confuse the reader.
Provide a compelling introduction that explains why studying the displacement of subway lines due to tunnel under-crossing is important. What are the potential consequences of not addressing this issue?
Comments for author File: 
Comments.pdf
Author Response
Dear Editor and reviewers,
We thank editor and reviewers for their valuable comments on our manuscript. In the following, we respond to these comments in the order of their appearance in your email.
Comment: Consider rephrasing the sentence: "In this study, we mainly investigate the displacement of subway line 11 induced by the under crossing of the Qianhai-Nanshan Integrated Drainage Deep Tunnel in Shenzhen." This sentence seems incomplete and may contain typographical errors.
Response: We have modified it. “We mainly study the deformation of the subway line 11 caused by the under crossing of the Qianhai-Nanshan Integrated Drainage Deep Tunnel in Shenzhen.”
Comment: If the terms "subsequent tunnel" and "under-crossing" have specific meanings in your context, make sure to define them clearly for the reader. Define any technical terms that might not be commonly understood by a general audience.
Response: We have modified the terms in the paper to ensure they are concise and clear.
Comment: Provide more details about the displacement monitoring data and the methods used for analysis. What techniques were employed for measurement and analysis?
Response: We have added relevant content in the manuscript.
Comment: Be specific about the results obtained from the analysis. What were the key findings related to subway line 11's displacement? How significant was the impact? Offer a more comprehensive discussion of the implications of the results. How can this information be practically applied to minimize disruption and ensure safety during subsequent tunnel construction? Expand on how the "displacement detection" measures could be practically implemented to control the impact of subsequent tunnel under-crossings. Provide examples or recommendations for construction planning and execution.
Response: During a new tunnel under crossing an existing subway tunnel, the deformation of the existing subway tunnel is paid more attention due to more deformation. Accurate monitoring instruments are applied to monitor the displacement of existing subway tunnel during the new tunnel under-crossing. Some monitoring cross sections are set along the longitudinal direction of the existing subway tunnel (shown in Figure 5). The excavation parameters, such as tunnelling speed, jacking forces, and grouting pressure, directly affect the deformation of the existing subway tunnel. Therefore, the development of deformation induced in the preceding of subsequent tunnel may reach the ultimate state and may take place in different patterns.
Comment: Specify the conditions under which the findings and guidelines are applicable. Are there specific types of tunnels, geological conditions, or urban settings for which these guidelines are most relevant? Include additional references that are relevant to related studies, research, or projects that support your findings or provide context for your work.
Response: The safety threshold of existing tunnel is based on the standard "Management Measures for Rail Transit Operation Safety Protection Zone and Construction Planning Control Zone Engineering" of Shenzhen City in 2021. The reference of Liu Shihu (2022) Analysis on the difference of geological survey between mining method and shield method in Qianhai deep tunnel project is adopted.
Comment: Provide a compelling introduction that explains why studying the displacement of subway lines due to tunnel under-crossing is important. What are the potential consequences of not addressing this issue?
Response: We have added relevant content in the introduction. The weathered granite strata would cause more deformation due to being prone to softening and disintegration after tunnelling, which would increase tunnelling risk especially when subsequent tunnel under crosses at a close distance. In addition, when there is more groundwater with higher pressure or groundwater is not treated properly, which would increase the risk of subsidence induced by tunnelling.
Reviewer 3 Report
This paper presents a field research on the tunnel structure behavior subjected to a newly built under -crossing tunnel with with a big diameter. Since there are many similar works presented, the current one is still potential because of its valuable data. Before this work could be considered for publish, some work should be done for improving this paper.
1. Some tyical case information such as tunnel diameters and ground water table location are missing.
2. The layers in table 1 do not match the layers in Fig. 3 and 4.
3. The monitoring points in Fig. 5 are not consistent with the legends in Fig. 7-12 ,which causes the figs hard to understand.
4. It is realized that the shield tunnel tail grouting serves as a important measure to decrease the negtive effect of the under-crossing tunneling, the authors should keep that in mind. For the under-crossing shield tunneling, how to perform tail grouting should be discussed. For the guidiance, some contributions are lised below for the authors to have a better understanding on tail grout.
References
[1] Liu, W., Liang, J., & Xu, T. (2023). Tunnelling-induced ground deformation subjected to the behavior of tail grouting materials. Tunnelling and Underground Space Technology, 140, 105253. https://doi.org/10.1016/j.tust.2023.105253
[2] X. Xie, Y. Yang, M. Ji. (2016) Analysis of ground surface settlement induced by the construction of a large-diameter shield-driven tunnel in Shanghai, China. Tunn. Undergr. Space Technol., 51:120-132
need to be improved
Author Response
Dear Editor and Reviewers,
We thank editor and reviewers for their valuable comments on our manuscript. In the following, we respond to these comments in the order of their appearance in your email.
Reviewer #3:
Comment: Some typical case information such as tunnel diameters and ground water table location are missing.
Response: We have added it in the manuscript.
Comment: The layers in table 1 do not match the layers in Fig. 3 and 4.
Response: We have modified the layers in Table 1.
Comment: The monitoring points in Fig. 5 are not consistent with the legends in Fig. 7-12, which causes the figs hard to understand.
Response: We added the numbers in Fig.5.
Comment: It is realized that the shield tunnel tail grouting serves as an important measure to decrease the negative effect of the under-crossing tunneling, the authors should keep that in mind. For the under-crossing shield tunneling, how to perform tail grouting should be discussed. For the guidance, some contributions are listed below for the authors to have a better understanding on tail grout.
Response: We agree your suggestion, we added some references and discussions.
Round 2
Reviewer 1 Report
Regarding the following comments and authors' responses to them:
"Comment: I propose that the authors should add a paragraph describing the geomechanical behavior of each geological formation of Table 1 towards the under-construction tunnel and refer to the potential consequences that may occur during the construction phase. This description is crucial for the monitoring process and can justify many problems that can arise during the excavation. To be more specific, in Fig. 3, a variety of weak geological formations are depicted (e.g., residual soil, fully weathered mixed granite, silt, coarse sand). The geomechanical behavior of those formations must be taken seriously into consideration during the excavation process and I think that some related remarks should be integrated into the under-review manuscript.
Response: We have made modifications to the content in Table 1 and added relevant content.
Comment: There is no written something about the potential role of groundwater regarding the measurement of monitoring data. Formations such as plain fill, coarse sand, residual soil, and weathered granite are susceptible to the infiltration of groundwater and as a result, this can affect the stability of the under-construction tunnel and its surrounding geoenvironmental. In my opinion, authors should dedicate a paragraph referring to that parameter (e.g., role of groundwater) also.
Response: Your suggestion is very good. We have added relevant content in manuscript.
Comment: It would be useful if the authors gave a more detailed description of the “hardware” or equipment of the monitoring system.
Response: We have added relevant content in Fig. 6."
I believe that some more explanations would add value to the scope of the manuscript.
For example:
Considering the first comment, there are more geological formations apart from the weathered granite that need to be analyzed in relation to the content of my comment.
Considering the second comment, I think that more explanation of the groundwater role would be written, by not just referring to general comments. Authors need to specify possible problems that can arise during the particular excavation process.
Lastly, considering the equipment of the monitoring process, a just-depicted figure is not accepted. They should add some information about the equipment technology.
Minor editing of English language required.
Author Response
Dear reviewers and editor,
We thank reviewers and editor for their valuable comments on our manuscript. In the following, we respond to these comments in the order of their appearance in your email.
Comment: Considering the first comment, there are more geological formations apart from the weathered granite that need to be analyzed in relation to the content of my comment.
Response: In this site, plain fill is widely distributed, with diverse components and uneven soil quality, making it a relatively unstable soil mass. The Quaternary Holocene series of marine land deposits contain organic sand and the Quaternary Holocene series of alluvial proluvial gravel sand are liquefiable sand with slight to moderate liquefaction potential. The plain fill and the sand layers are located in the shallow strata and far above the tunnel, which have less influence on the tunnel. Residual soil, fully and strong weathered rock are vulnerable to softening when they are disturbed from tunnel crossing through due to their poor physical properties, which may cause excessive deformation and even threaten the safety of tunnel.
Comment: Considering the second comment, I think that more explanation of the groundwater role would be written, by not just referring to general comments. Authors need to specify possible problems that can arise during the particular excavation process.
Response: The tunnel is located within a relatively impermeable layer, while there are some fissures in weathered rocks where tunnel crosses, and groundwater may form concentrated seepage. The weathered granite strata would cause more deformation due to being prone to softening and disintegration after tunnelling, The seepage of groundwater will further expand the plastic zone of tunnel surrounding rock, and then affect the stress distribution and deformation of tunnel surrounding rock. The stress release caused by tunnel excavation in saturated rock mass is a nonlinear development process with complex temporal and spatial effects accompanied by seepage. The coupling effect of seepage field and stress field in groundwater seepage during excavation will aggravate formation deformation and may lead to catastrophic accidents such as water gushing and collapse. Therefore, stratum reinforcement measures must be taken before tunnelling through such geological section, especially when under-crossing the existing subway tunnel. In order to enhance the strength and modulus of surrounding rock, reduce the permeability of surrounding rock and improve the stability of surrounding rock, grouting is the most commonly used measure of formation reinforcement in tunnel engineering, and pre-grouting technology is an important means to ensure the safety and quality of construction.
Comment: Lastly, considering the equipment of the monitoring process, a just-depicted figure is not accepted. They should add some information about the equipment technology.
Response: Your suggestion is good. In actual engineering, these monitor data can be used to evaluate the risk grade based on a comprehensive evaluation model of tunnel risk based on the cloud model and combination weight. According to the characteristics of the risk influencing factors of the tunnel, four levels (lower risk, medium risk, higher risk, and highest risk) are given according to the trial version of the risk standard based on former analysis. The risk grade can be obtained by the evaluation model from time to time, when the risk grade reaches higher risk grade, tunnelling speed should be shut down and some treatment measures such as grouting and pumping should be strengthened. In this paper, we mainly analyzed displacement patterns base on the monitor data and did not do more research on the monitoring system.
Author Response File: 
Author Response.docx
Reviewer 3 Report
The modifications are affirmed and the efforts for paper improving are appreciated. The current work is recommended for publication.
Author Response
Dear reviewer,
Thanks for your reviewing.
