An Operating Model for an EPB Shield TBM Simulator by the Correlation Analysis of Operational Actions and Mechanical Responses

Round 1

Reviewer 1 Report

This manuscript aims to develop an operating model for application in a TBM operating simulator. Detailed operation procedures and interlock and warning alarm systems were designed for the operating model. Several simulation tests verified the operating model for the TBM operating simulator under the different conditions. Based on my review, I believe that the authors must delve a bit more on the limitations of their study, and the novelty of their results. The following comments are recommended during the revision of the paper.

 

General comments:

• Authors performed a multiple regression analysis for predicting the shield operational parameters, but what are the input parameters that used for this prediction? Otherwise, what are the sensitivity analyses of these parameters? In addition, the statistical analysis of these parameters should be provided.
• Authors presented the results of multiple regression analysis of soil excavation for (a) thrust, (b) cutter head torque, (c) rotation speed, and (d) advance rate. However, the used data are very limited to present an accurate model. Hence, the presented results are difficult to accept in this manner.
• As clearly known, the shield operational parameters depend mainly on geological conditions, however, no effective information for the used geological conditions or its specific properties in this study.
• In this work, operating procedures are established, and interlock and warning alarm systems are designed for use in the operating model. How the authors designed interlock and warning alarm systems? Otherwise, how did the authors extract and collect the used data?
• Authors need to present the main benefit from presenting Figs. 7-12? How these results can be benefit to the reader?
• Authors indicated that the operating model was verified in several simulation tests. However, this verification is vague and needs to be clearly presented.

Specific comments

• Line 35-50: It is necessary to present the main shield operational parameters, which affecting the tunnel performance based on the recent studies using soft computing techniques (e.g., Engineering, 2021, 7(2), 238-251. https://doi.org/10.1016/j.eng.2020.02.016.); (Appl. Ocean Res., 2020, 101: 102223); (Adv. Eng. Inform., 2021, 45: 101097).
• The challenges of excavation in complex strata need to be highlighted;
• The introduction needs to be well organized again. Authors need to clearly present what is the different between this study and current literature? What is the new in this work?
• Line 119: Authors observed that the independent variables comprised the ground conditions and TBM specifications, e.g., Gravel, sand, & silt. How was the geological conditions adapted in the regression model?
• Line 166-168: Authors mentioned that the estimated thrust and cutterhead torque requirements increase with increasing diameter, whereas the estimated rotation speed and advance rate requirements decrease. How can the authors verify this information?
• Verification of regression equations for soil excavation that presented in Fig. 3 is not enough. Try to use more statistical metrics such as RMSE, MAE, etc.
• Line 181-182: authors need to focus on the main contributions and neglect the ineffective information.
• Line 202: how was 143,514 data points collected?
• Line 202-204: why did the authors normalized the data?
• Based on section 3.2, the correlation coefficient R² is very low as no effective contributions can be detected from this part.
• Architecture of excavation procedures that applied in the TBM operating simulator has been presented in Fig. 4, but this figure is vague and difficult to reader.
• Line 310: Procedure for resolving a warning in the operating simulator that presented in Fig. 5 should be clearly discussed.
• What is the benefit from Fig. 6?
• Based on Figs. 7-8, how do you specify the error in the reading or warning conditions?
• Line 371-373: To decrease the thrust, the shield jack speed was decreased from 40 to 24 mm/min; this reduced the thrust to 38,059 kN and also changed other mechanical responses. What is the benefit from this figure?
• Line 400-430: the results that presented in conclusions are very superficial and authors need to present the novel results of this study.

Author Response

We thank the reviewer for your thoughtful comments, which we have accommodated as indicated in the comments below with resulting improvement of the paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

This article aims to propose a tool for simulating tunneling with a TBM. Two steps are necessary to do this:

• to find a mathematical expression linking the characteristic parameters of the TBM response (advance speed, torque on the cutting wheel, etc.) as a function of the input data (mechanical characteristics of the ground and TBM control parameters),
• to implement these equations in a graphical interface and to propose to the user scenarios of variation of the various input data.

According to us, the first of these objectives is not fully achieved here, for the following reasons :

• the correlations presented are defined on the basis of ten points (one value per construction site). This number of data is much too low: on a given site, each parameter can easily vary by a factor of 2 to 3;
• the reader would like to know precisely the origin of the different data (name of the site and associated bibliographic reference), to be able to judge the reliability of each data;
• the correlations are built on a limited number of parameters, ignoring several essential parameters. First of all, the nature of the ground. This is partially taken into account in Table 1, but then disappears, even though it is the essential parameter, totally conditioning the response of the TBM. The injections of foaming solution and polymer into the cutting chamber are also not included, even though they directly affect the value of the torque on the cutting wheel.

The second objective (simulation tool) is not achieved either. The second objective (simulation tool) is also not achieved. To begin with, the objective of this simulator is not entirely clear. In our opinion, the objective of this type of tool is to train a future TBM pilot, which imposes the following points, which are not respected here:

• the need for a graphical interface identical to that of a conventional TBM: this does not seem to be the case here. Was a partnership with a TBM manufacturer conducted as part of this research?
• the need to integrate all aspects of control: to check that the machine's capacities are not exceeded (thrust force and torque on the cutting wheel for example), of course, but also to respect the machine's guiding tolerance, to respect the criteria of displacements induced in the terrain, to obtain excavated materials of good consistency, etc. The proposed tool focuses solely on the first point;
• the need to impose scenarios of variation of certain input parameters "external to the TBM" (changes in the mechanical characteristics of the ground in particular) on the driver in order to see how he modifies his control of the machine. These scenarios, the associated pilot response and the TBM response deduced from these two points are not presented here.
  
  

Author Response

We thank the reviewer for your thoughtful comments, which we have accommodated as indicated in the comments below with resulting improvement of the paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

acceptable but the editorial problem should be solved, e.g. reference [5] and [6] should give full list of the authors' name.