Load-Bearing Characteristics of PHC Piles Constructed by the Inner Digging Method Based on Ultimate Load Testing and Numerical Simulation
Round 1
Reviewer 1 Report
The manuscript entitled "Load-bearing characteristics of PHC piles constructed by the inner digging method based on ultimate load testing and numerical simulation" is not acceptable for publication in it's present form due to the following reasons:
Similar research has been previously conducted by Zhao et al. (2013). However, the results obtained from the present study do not match with the results obtained by Zhao et al. (2013) in terms of the ultimate load bearing capacity of PHC piles by inner digging and hammering methods. Adequate justification should be provided for the discrepancies in the results between the two studies.
The rebound Q-S curves for the specimens should also obtained using the finite difference method and compared with the corresponding test curves.
The maximum load carrying capacity of the piles as obtained from the finite difference analysis results do not match with the test results.
The comparison of experimental and analytical stress/strain values of the two specimens should also be included.
The effect of variation of prestressing force due to prestress losses on the performance of the piles should be investigated.
Bearing capacities of PHC piles by other methods such as vibratory pile-sinking methods and others should also be compared with respect to the inner digging method.
Some latest publications on the topic (Zhou and Fang, 2015. etc ) have not been cited.
Author Response
Thank you very much for your suggestions for the manuscript, we have made the changes as requested, more details are in the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Respected Authors
It is a nice study with possible practical outcomes, based on real world field experiment and numerical modeling in FLAC. I appreciate it.
I listed below some editorial issues concerning the format of the reference list and the way that references are addressed in the body text.
1. Please use consequently MDPI reference format [number] in the body text. All references should be listed in order of appearance. Check lines 45, 48, 53, 57, 63, 68, 77-79, 85, 89, 93, 101, 103, 105, and use proper format.
2. Please try to avoid group references in your introductory part. Presented "Stat of the Art" report should provide some very basic information about every cited paper. You may refer to a couple of papers like [31, 32] but [19-25] seems to be too much (7 items in one reference). But it is just my opinion.
3 Provide a proper format of the reference list according to MDPI template.
Respected Authors
I have an impression that you should provide some more detailed explanation (maybe some reservations) concerning interpretation of Static Load Testing (field pile testing). The final steps of the test were planned at 4800 kN and 7200 kN respectively. I did not notice (maybe I missed it) why the range of the test results in figure 5 is limited to 4000 kN and 6000 kN respectively. In my opinion you missed a chance for a precise evaluation of both piles' capacity, because assuming pile capacity equal to the last stage of the test tends to underestimate the ultimate value. Limiting of the range of field studies decreases the possibility of proper calibration of your FD numerical model (FLAC). Please comment on that issue and maybe make some reservations.
Anyway, I believe that after cautious smoothing, your study will deserve publication, so I marked just minor revision.
Sincerely
Author Response
Thank you very much for your suggestions for the manuscript, we have made the changes as requested, more details are in the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The reviewer does not have any further comments.
The manuscript can be accepted in it's present form.
