Analysis of the instability conditions and failure mode of a special   type of translational landslide using long-term monitoring data:  a case study of the Wobaoshi landslide (in Bazhong, China)

Liu, Yimin; Wang, Chenghu; Gao, Guiyun; Wang, Pu; Hou, Zhengyang; Jiao, Qisong

doi:https://doi.org/10.5194/nhess-20-1305-2020

Articles | Volume 20, issue 5

https://doi.org/10.5194/nhess-20-1305-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/nhess-20-1305-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 20, issue 5

Research article

|

14 May 2020

Research article |

| 14 May 2020

Analysis of the instability conditions and failure mode of a special type of translational landslide using long-term monitoring data: a case study of the Wobaoshi landslide (in Bazhong, China)

Yimin Liu, Chenghu Wang, Guiyun Gao, Pu Wang, Zhengyang Hou, and Qisong Jiao

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Final revised paper (published on 14 May 2020)
Preprint (discussion started on 23 May 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'discussion', Anonymous Referee #1, 05 Jul 2019
- AC1: 'Reply to the reviewer 1#', Yimin liu, 24 Jul 2019
SC1: 'Discussion on the paper by Y. Liu, C. Wang, G. Gao, P. Wang, Z. Hou, Q. Jiao', Felix Darve, 24 Jul 2019
- AC2: 'Reply to professor Darve', Yimin liu, 26 Jul 2019
RC2: 'review report on paper 2019-133', Felix Darve, 25 Sep 2019
- AC3: 'Reply to the professor Darve#', Yimin liu, 26 Sep 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (further review by editor and referees) (01 Oct 2019) by Paola Reichenbach

AR by Yimin liu on behalf of the Authors (01 Oct 2019)

ED: Referee Nomination & Report Request started (14 Oct 2019) by Paola Reichenbach

RR by Felix Darve (16 Oct 2019)

RR by Anonymous Referee #3 (31 Jan 2020)

Suggestions for revision or reasons for rejection

I read the second version of the paper, the review reports regarding the version 1 and the corresponding responses of the Authors.
The landslide case history discussed in this paper is interesting but in my opinion the second version of this paper too suffers from some weak points.
They are the following:
1) language style and language grammar are confused;
2) text not well organised: some repeats, some references cited not by way
3) deficiencies of some experimental data: shear resistance angle, cohesion, elastic moduli
4) some doubts about the landslide type. What about the interpretation of this process as a lateral spread of which you are observing a part (the translation of two blocks triggered by increase of water level in two cracks)? I’m supposing a lateral spread involving a gentle slope constituted by alternation of strata gently inclined downslope and incised at its base by a river.
5) some doubts about your interesting interpretation. You discussed the results of the numerical simulation of one cycle of increasing and decreasing water level in cracks I and II. You discussed only qualitatively the hypothesis of the effects induced by more cycles; I’m not sure that numerical simulation of more cycles would be so reliable!

Detailed comments:

Line 42: Fausto G. et al., 2004; probably Guzzetti et al., 2004
Line 43: “Research on the formation mechanism and deformation mode of a translational landslide is mainly based on two perspectives”. To which research are you referring?

Line 46: Kong and Chen, 1989 is lacking in the list of references
Line 51-52: “…the hard rock layer covered by the upper layer (such as granite and sandstone) has a crushing effect on …the lower weak rock layer”. I dont understand.
Line 56-57: “Sensitive safety factors”. What are? Probably you are meaning sensitivity analysis of safety factors or something like that.
Line 57: Fan Xuanmei et al. (2008) is not listed in the references
Line 62: Mario et al. (2008): I think that this reference is Floris et al., 2008 (or Floris et al., 2008). Please modify also in the reference list.
Line 66: landslide resurrection. Are you meaning landslide reactivation?
Line 73: collation. I suppose collection
In my opinion the part of the text between line 43 and line 76 is not useful. I suppose that it represents the good intention of the authors to discuss the state of the art about translational landslide but I think it is out of the scope of the paper and, in any case, in the present version largely incomplete (very hard task to do and the selection proposed by the Authors seems a bit random. For example, why do you list papers discussing the application of geophysical survey to investigate a translational landslide or papers dealing with ETM and DEM? ).
Lines 86-87: “….laboratory physical experiments have been conducted in the to verify the failure model.”. Please verify english language.
Line 90: abtained. Probably obtained.
Line 77-92: I suggest to summarise. This part of the text is too long.
Line 100: Engineering instead Enginereing This mistake is common in the text. Please verify.
Line 110-111: I suppose that the meaning of the sentence is “the landslide involved sandstone and mudstone belonging to the Penglaizhen Formation of the upper Jurassic” . Is it right? If yes, I suggest to revise the text
Lines 120-121: I suppose you are discussing about water filling primary porosity (voids between grains) and water filling secondary porosity (cracks). I suppose that the first characterises weathered rock and the second jointed rock. Is it right? If yes, I dont understand the relevance of this sentence in your description; moreover I dont undesrtand the meaning of “trailing edge”.
Lines 102-122. In my opinion the content of this part of the text doesn’t deal with field survey as the title of the paragraph states
Line 129: 105 instead 105
Fig. 2: Please add some geologic data. Outcropping formation/lithology, attitude of the strata in the surveyed area. I have some doubts about your section I-I’. If the trace of the section is right, the building and the highway should be located more or less in the middle of the section? Why they are located on the SW side? The values of the contour lines are lacking in the map. I suggest to deeply revise this figure!
Line 126: How exactly you define the landslide boundary?
In my opinion in your paper you have to avoid the term “about horizontal” or slide horizontally. The strata are gently inclined downslope and the failure surface too!
Line 145: “multistage dangerous rock mass with dumping deformation”. I dont understand
Line 146: “the inclination of the landslide is almost erect”. What does it mean?
Line 147: “thin plate” probably “narrow plate”
Line 148: “furthermore, the surface structure of the slope has a certain degree of aperture “. What does it mean?
Line 149: “collapse deposits “; you are meaning debris?
Lines 174-181: From a technical point of view this description is lacking and it anticipated your interpretation of the monitoring data.
The title of this section “Forming conditions” doesn’t reflect the content. You are describing the landslide area.
Fig. 4: What is “platform” marked by dashed blue line?
I suggest to add some tecnical details of the used instrumentation, especially for pore water instrumentation.
Lines 204-205. hs or hm?
Lines 255-256: Why do you think that the total cumulated displacement (0,2m from Figure 8) is induced by rainfall? From your data set you can infer that the increasing/decreasing width of the two cracks are strictly related to the rainfall.
What “plate girder” is?
Lines 269-277. “…owing to the sudden decrease of the pore-water level in the trailing edge crack, the water pressure around immediately following plate-shaped body becomes unbalanced, and new sliding damage is induced…”. I dont understand this theoretical explanation. Probably an outline referred to this landslide would help.
Line 285: “And soli elastic-perfectly….” ?
Line 295: h1 and h2 are the height of the water level in the crackI and II respectively. Why pore water level?
Line 300: In fig. 8 h is lacking
Line 301: “…internal cohesive force of the sliding surface”. Are you discussing about the cohesion of silty-mudstone? or of the stratification joint of the silty mudstone. In other words, did you derive this value from laboratory tests (triaxial test) performed on some intact samples of silty mudstone (as reported in your response to reviewer 2) or did you test a stratification joint? In my opinion you have to improve the discussion about the choice of the shear strength parameters (cohesion and shear strength angle).

I suggest to add one Figure (Figure 9b) showing the vectors representing each one force considered for equations 1 and 3 (resisting forces: 3 components; acting force: 2 components).

Line 304: I suggest “unit weigth of the saturated volume” instead of “saturated gravity”, unit weight of water instead of gravity water.

Line 309: “experimental data of the triaxial confining pressure”. I suppose you are discussing the experimental data of the triaxial test not of the triaxial confining pressure that is a detail of the triaxial test.

Line 333 and Figure 10: “slippage”. I think you mean the displacement or, better, the variation of aperture of the cracks I and II you call absolute stretching.

Line 333: “increase” instead change

Caption of Figure 10: if I understand well (see your text too) you are showing the measured h in correspondence of the sudden increase of aperture of the cracks not the maximum values of the measured h.

Line 342-343: In my opinion in Fig. 10 you didn’t show the equation 1 and 3.

Line 348: “values” instead “frequency”

Line 357: how did you infer elastic moduli? ; “angle”, instead “angel”

Lines 367-371. Already reported

Line 373: “change period shown in Table 5”? I suppose in five loading steps

Caption of Table 5: Simulated values of h1 and h2

Your simulation is referred to one cycle of increasing and decreasing water level in crack I and II.
If you introduce in your simulation some other cycle of increasing and decreasing water level (as it results from your monitoring data) what it happen to the block I and II?

Lines 393-400. In my opinion it is a repetition

Line 406: Why did you mention the paper of Zhang et al. 1994?

Line 414: Fan et al., 2007

Lines 426-436: I suggest to improve this explanation. Your interpretation is very interesting but it explains 1 cycle of increasing and decreasing water level in crack I and II. What would be the effects of the successive application of some other cycle?

Lines 448-456: In this part of the text there is a summary of section 4.1. It is a not useful repetition.

Lines 447-455: The position of this part of the text discussing the low value of shear resistance angle is inappropriate; in my opinion, as already suggested, you have to discuss the experimental data before using them for your calculations. Moreover, the discussion about the dilatancy is confused.

Line 452/453: “laternal infinite” ?

Section conclusion might be significantly summarised.

Caption of Table 3: In column 2 and 4, values of aperture of crack I and II are reported? If yes I suggest to modify the corresponding title of the two columns (see also the text).

Table 4: What is gravity?
You report some data about clay. If I consider Figure 2, I didn’t find clay. Is it a layer inside the silty mudstone?

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ED: Publish subject to minor revisions (review by editor) (03 Feb 2020) by Paola Reichenbach

AR by Yimin liu on behalf of the Authors (10 Feb 2020) Author's response Manuscript

ED: Publish subject to minor revisions (review by editor) (19 Feb 2020) by Paola Reichenbach

Dear Yimin Liu,
I have read your article “Analysis of the instability conditions and failure mode of a special type of translational landslide using long-term monitoring data: A case study of the Wobaoshi landslide in Bazhong，China). The topic of the article is interesting but the manuscript needs to be completely revised by an English-speaking person to bring it up to an international level before it can be published in an international journal. In additional you should use international terms in the text.
Some figures need to be revised to be readable, fonts are too small and patterns not always easy to read.

In addition, I do think you have properly answer to the following comments formulated by one referee:
1) language style and language grammar are confused;
2) text not well organised: some repeats, some references cited not by way
3) deficiencies of some experimental data: shear resistance angle, cohesion, elastic moduli
4) some doubts about the landslide type. What about the interpretation of this process as a lateral spread of which you are observing a part (the translation of two blocks triggered by increase of water level in two cracks)? I’m supposing a lateral spread involving a gentle slope constituted by alternation of strata gently inclined downslope and incised at its base by a river.
5) some doubts about your interesting interpretation. You discussed the results of the numerical simulation of one cycle of increasing and decreasing water level in cracks I and II. You discussed only qualitatively the hypothesis of the effects induced by more cycles; I’m not sure that numerical simulation of more cycles would be so reliable!

I have added further comments in the attached text. I didn’t add detailed comments in chapters 3,4 and 5 that need to be rephrased to be well understand by an international audience.

Comments to the Author: PDF

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AR by Yimin liu on behalf of the Authors (02 Mar 2020) Author's response Manuscript

ED: Reconsider after major revisions (further review by editor and referees) (19 Mar 2020) by Paola Reichenbach

AR by Yimin liu on behalf of the Authors (14 Apr 2020) Author's response Manuscript

ED: Publish as is (21 Apr 2020) by Paola Reichenbach

AR by Yimin liu on behalf of the Authors (22 Apr 2020) Manuscript

Short summary

We considered a translational landslide exhibiting an unusual morphology, i.e., the Wobaoshi landslide. The deformation and failure mode of the plate-shaped bodies were analyzed and investigated based on numerical simulations and calculations. The monitoring data and geomechanical model proved that the accumulated water pressure in cracks causes the plate-shaped bodies to creep. Therefore, these research findings are of reference significance for the rainfall-induced translational landslides.