Feasibility Study on Grouting Compactness Detection in Sleeves Using Piezoelectric Transducers
Round 1
Reviewer 1 Report
This study explored the feasibility study on grouting compactness detection in sleeves using piezoelectric transducers. Experimentally, a Lead Zirconate Titanate (PZT)-based sleeve grouting compactness detection method was systematically investigated. Moreover, the wavelet packet energy (WPE) and Hilbert Huang transform (HHT) signal processing methods were used to analyze the signals received by the PZT sensor. The following comments are suggested:
Before performing wavelet packet analysis, preliminary processing of the original data is needed, such as correcting the distortion of the waveform, reducing the interference of noise, improving the signal-to-noise ratio, and highlighting some details of the signal. The author should explain the relevant disposal methods. The wavelet functions used in wavelet analysis are diverse, and the results of applying different wavelet basis functions are different. The author should explain the wavelet function used. HHT is an advanced technique for time-frequency analysis of signals, applicable to both non-linear and non-stationary temporal signals. It is recommended that the authors draw a process diagram of the Hilbert-Huang conversion process. Unlike the wavelet transform, HHT does not need to preset any basis functions. Instead, it uses its unique decomposition mode (EMD or ensemble EMD, EEMD) to decompose the temporal signals into certain intrinsic mode functions (IMF). Through the HHT of each IMF component, the instantaneous frequency at any moment can be estimated, a procedure that can show finer temporal variations in the frequencies of the signals. The authors should compare the results of the two analysis methods and make recommendations from them. Several IMF functions obtained during the signal decomposition process of HHT must meet the following conditions: (1) the sum of the positive and negative values of the function must be the same as the zero-crossing point, or at most they differ by 1; (2) The upper and lower envelopes formed by the extreme values have an average value of zero. The authors should expound in the article. In the test for the grouting compactness detection of sleeves, the grouting compactness was controlled by the cavity areas of the rubber plugs. The rubber plugs were placed at the ends of the sleeves. What is the length of the rubber plugs? Section 4 "Test Results and Discussion" should be the focus of the entire article, but there are only two paragraphs. The author is advised to further explain the issues of signal preprocessing, wavelet base selection, wavelet packet analysis, and application of HHT signal chirping.Author Response
Responses to Reviewers’ Comments on
Feasibility Study on Grouting Compactness Detection in Sleeves Using Piezoelectric Transducers
By Chen Wu, Chao Yang, Shenglan Ma and Xiaoliang Xu
The authors wish to thank the reviewers for their time in reviewing our manuscript and constructive comments. The comments are addressed accordingly in the new revised manuscript, and the detailed responses are provided below:
Point 1: Before performing wavelet packet analysis, preliminary processing of the original data is needed, such as correcting the distortion of the waveform, reducing the interference of noise, improving the signal-to-noise ratio, and highlighting some details of the signal. The author should explain the relevant disposal methods.
Response 1: The authors revised it in the revised manuscript, including :(1) Specimens were Pre-swept frequency before the formal test, determined the sweep frequency range and reduced the error; (2) Each specimen was scanned for 5 consecutive times, the first and last times were removed and the average value of the remaining three times was taken as the original signal; (3) wavelet transform method itself has noise elimination function. More details in Section 3.2 and first paragraph of Section 4.1.
Point 2: The wavelet functions used in wavelet analysis are diverse, and the results of applying different wavelet basis functions are different. The author should explain the wavelet function used.
Response 2: Sym8 has the characteristics of compact support set, good continuity and symmetry, it is more suitable for denoising signals with good continuity. Moreover, the information loss of the signal is serious in the case of 5-layer decomposition. Therefore, wavelet basis function was sym8 and decomposition layer was set as 4. The authors revised it in Section 4.
Point 3: HHT is an advanced technique for time-frequency analysis of signals, applicable to both non-linear and non-stationary temporal signals. It is recommended that the authors draw a process diagram of the Hilbert-Huang conversion process.
Response 3: The authors revised it in the revised manuscript.
Point 4: Unlike the wavelet transform, HHT does not need to preset any basis functions. Instead, it uses its unique decomposition mode (EMD or ensemble EMD, EEMD) to decompose the temporal signals into certain intrinsic mode functions (IMF). Through the HHT of each IMF component, the instantaneous frequency at any moment can be estimated, a procedure that can show finer temporal variations in the frequencies of the signals. The authors should compare the results of the two analysis methods and make recommendations from them.
Response 4: We added a comparison of the two analysis methods in third paragraph of Section 4.4. When the fault tolerances of the two methods are same, the HHT method did not consider the basis functions and the level number of decompositions. As a result, the authors recommend used HHT method to detect grouting compactness.
Point 5: Several IMF functions obtained during the signal decomposition process of HHT must meet the following conditions: (1) the sum of the positive and negative values of the function must be the same as the zero-crossing point, or at most they differ by 1; (2) The upper and lower envelopes formed by the extreme values have an average value of zero. The authors should expound in the article.
Response 5: The authors added it in Section 2.3.
Point 6: In the test for the grouting compactness detection of sleeves, the grouting compactness was controlled by the cavity areas of the rubber plugs. The rubber plugs were placed at the ends of the sleeves. What is the length of the rubber plugs?
Response 6: The authors added it in line 162.
Point 7: Section 4 "Test Results and Discussion" should be the focus of the entire article, but there are only two paragraphs. The author is advised to further explain the issues of signal preprocessing, wavelet base selection, wavelet packet analysis, and application of HHT signal chirping.
Response 7: The authors revised it in the revised manuscript.
Once again, thank you very much for your comments and suggestions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This paper deals with the non-destructive evaluation of Grouting Compactness in Sleeves.
The main contribution with respect to the existing methods is the possibility to estimate the defective level and this is achieved by using Piezoelectric Transducers ( able to convert pressure into voltage difference and voltage into deformation).
The extracted sinusoidal signal was processed by using the wavelet packet energy (WPE).
The total energy observed over time is the output signal to be observed. It was processed by the Hilbert-Huang Transform Method and the Hilbert energy observed over time.
The approach is convincing since the authors demonstrated that some classical issues are fixed by the proposed approach.
Anyway, some concerns arose along reading the manuscript.
First of all, I suggest to explicitly indicate how HHT is exploited to analyze the signal and to correlate its output to defects. I understood that peak related indexes are introduced but I expected to know them while reading section 2. As a consequence, I suggest adding a couple of paragraphs at the end of section 2 (just before starting the experimental section).
Moreover, Is it possible to add some more experiments? Is there some boundary condition that could affect results? A discussion about that could help the reader.
An additional suggestion is to reference a couple of very related works in which HHT or WPE were employed for non-invasive inspection i.e.
M Leo, D Looney, T D’Orazio, DP Mandic, Identification of Defective Areas in Composite Materials by Bivariate EMD Analysis of Ultrasound, IEEE Transactions on Instrumentation and Measurement 61 (1), 221-232
Sampath, S., Bhattacharya, B., Aryan, P., & Sohn, H. (2019). A Real-Time, Non-Contact Method for In-Line Inspection of Oil and Gas Pipelines Using Optical Sensor Array. Sensors, 19(16), 3615.
Author Response
Responses to Reviewers’ Comments on
Feasibility Study on Grouting Compactness Detection in Sleeves Using Piezoelectric Transducers
By Chen Wu, Chao Yang, Shenglan Ma and Xiaoliang Xu
The authors wish to thank the reviewers for their time in reviewing our manuscript and constructive comments. The comments are addressed accordingly in the new revised manuscript, and the detailed responses are provided below:
Point 1: First of all, I suggest to explicitly indicate how HHT is exploited to analyze the signal and to correlate its output to defects. I understood that peak related indexes are introduced but I expected to know them while reading section 2. As a consequence, I suggest adding a couple of paragraphs at the end of section 2 (just before starting the experimental section).
Response 1: The authors add it in first paragraph of Section 2.3 and Section 4.3 with a process diagram of the Hilbert-Huang conversion process.
Point 2: Moreover, Is it possible to add some more experiments? Is there some boundary condition that could affect results? A discussion about that could help the reader.
Response 2: For the first question, the research work is only in stages at present, and some more experiments will be added in the future. The boundary condition of affect results is a good comment, such as the height of the rubber plug, the sweep frequency range, the treatment method and so on, which will be studied in the future.
Point 3: An additional suggestion is to reference a couple of very related works in which HHT or WPE were employed for non-invasive inspection i.e.
Response 3: The authors added the references in the revised manuscript.
Once again, thank you very much for your comments and suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors did not improve adequately the paper since no additional experiments and discussion about boundary conditions have been added.
I' still not fully convinced that the paper is suited for publication, even if it can result in interest for the readers.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The authors added some experiments that allow the paper to be suitable for publication.
