Comprehension of Seismic-Induced Groundwater Level Rise in Unsaturated Sandy Layer Based on Soil–Water–Air Coupled Finite Deformation Analysis

Round 1

Reviewer 1 Report

The authors use a standard code, applied to evaluate the elastoplastic deformation of a coupled soil-water-air system, in order to study the rise in groundwater level induce by the main shock and the aftershock of the Tohoku Earthquake emphasizing that the reported solutions cannot be obtained without such model (for example, with a linear elastic model using Biot´s theory).

I found this is an interesting study where the phenomenon of  ‘deformation-drainage-rise of the water level’ in the unsaturated upper layer of the soil is correctly performed and properly  addressed.

The structure of the paper, which provides the details of the analysis of the applied model in the Appendices, seems to me to be correct due to the mathematical complexity. I am not a specialist in the use of this code and cannot comment on it.

In my opinion, this is an interesting paper for the readers of the journal Water, which in the future should be extended (as the authors point out in the conclusions) to determine the influence of factors such as horizontal displacements, initial groundwater level and others. I think it should be published after considering the following comments:

Mayor comments:

1.- It would be convenient to justify the choice of a 1D model, based on the lithographic structure of the terrain, if it is possible. A lithographic cross section, in addition to Figure 2(b), would help to justify this choice. Perhaps, the discrepancy in the results provided by a 2D model could be somehow significant.  

Boundary conditions of each phase (water, soil and air), well described in lines 86-96, should be collected in a detailed figure for further illustration.

Minor comments:

1.- Rewrite lines 35-37

2.- Figure 4. Initial value is a black line, not a point. Initial pore water pressure and initial pore air pressure are the same. It is not necessary to depict two sub-pictures.

3.- What is the Midorikawa equation? (lines 136-137). An explanation of its applicability would make the roll of this equation to change the velocity V_s clear.

4.- A justification of the application of the same boundary conditions during and (above all) after the main shock (lines 140-141).

5.- Fourier amplitude spectrum is not really contributing much. Can you justify he need of including it?

6.- It would be interesting to monitor the soil density (bulk density) before, during and after the deformation. Can you include any of this information? Would it be interesting to include the effect of different initial voids ratio on the model? It is just curiosity and a suggestion; it is not necessary to include it in the manuscript.

7.- Consolidation and compression are related concept but, they have a temporal dimension that differentiate one from other (clays and sand, plastic and elastic). Are sand undergoing consolidation? are clays undergoing immediately deformation? Did the sand accumulated and increase of water pressure? please, dedicate a few lines to this aspect.

Author Response

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Reviewer 2 Report

Comments for author File: Comments.pdf

Author Response

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Reviewer 3 Report

The paper presents results of numerical modeling of seismic-induced impact on groundwater level and discussion on the influence it can take for environment and constructions. The complex three-phase model is used in one-dimensional approach. It is particularly shown that aftershock increases the possibility of liquefaction that increases the risk of accomplishable damage. In my opinion, the manuscript can be published after minor revision.

Comments to the authors.

1. The notation to Fig. 2 is unclear. That is “Analytical cross section”? Why it is “Analytical”? Description of this figure is poor.

2. Line 86. “The periodic boundary condition was set at the lateral sides”. How it is possible for one-dimensional modeling? Moreover, I have not found any formulas describing boundary conditions in the main text as well as in Appendix A. Boundary conditions must be given by equations.

3.  The manuscript should be checked for poor sentences that difficult for understanding. Some examples are given below:

- “The main shock leads to consolidation drainage after the main shock”

- “Aftershock increases the possibility that the expanded saturated area will also liquefy, increasing the risk of liquefaction damage”

- “the analytical results shown in this paper can only be obtained using “three-phase coupled,” “elastoplastic,” and “finite deformation” analysis” (Why are there so many quotes?)

- “In Section 2, the analytical conditions are described” (What is “analytical conditions”?)

- “This study will, for example, provide insights into liquefaction of ground subjected to continuous earthquakes”

Quality of English should be improved.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

All comments have been addressed.

In my view, one small comment has not been adequately addressed. I am concerned about using the right words to cite a particular phenomenon. 

Liquefaction in sands does not imply consolidation, but compression. The basic literature in soil mechanics generally restricts the use of consolidation to the long-term dissipation of water and excess water pressure over time. It is related to the weight of the soil. The concept of overconsolidation or normally consolidated would otherwise be meaningless.

In laboratory tests or, for example, in the construction of embankments with granular material, we use energy (vibrations and shocks) to compress unsaturated sands, a process in which the excess water pressure is also dissipated in a short period of time.

Authors answered to that previous comment as follows:"liquefaction of loose sand is a phenomenon in which plastic volume compression due to cyclic shear under the undrained condition causes a decrease in mean effective stress and an increase in excess pore pressure, which dissipates with time after the earthquake, resulting in compression, it is more appropriate to use consolidation. Therefore we have not taken any particular revision in this case"

I would include in the manuscript a similar simple but interesting basic theoretical explanation with the following clarifications:

- "the compression of the plastic volume due to cyclic shear in the undrained condition causes an increase in excess pore pressure and, consequently, a decrease in the mean effective stress."

- The word consolidation should be changed to compression or, if insistent, explain in the text why it is decided to call it sandy consolidation.

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The manipulation that the word consolidation has undergone since the first definitions made by Terzaghi, Peck, Harr, Atkinson, Scott, Taylor..., is typical of our cultural evolution. Having worked in consolidation for more than 10 years, I have been able to confirm this reality and I find it difficult to reverse the situation.

I appreciate your use of the term in inverted commas. Congratulations on your work.

Author Response

Thank you for your comment very much.