Gravitational Deformation and Reactivation Mechanism of a Fault-Bounded Slope, Eastern Yanshan Mountains, China
, Tiantao Li 1,*, Xiangjun Pei 1, Jian Guo 2, Jingjing Tian 1, Shoudao Wang 1,3 and Mingfang Pu 1
Round 1
Reviewer 1 Report
1.Table 1 in section 3 is called as “ Toppling intensity grading system of the Nandongzi landslide”. The table describes four zones: Down-slope zone, Overlapping zone, Highly toppled zone and Weakly toppled zone. But nothing was previously said in the text about the division into zones. The zoning information appears much lower, only in section 4.
2. Table 2 is called as “Toppling intensity grading system of the Nandongzi landslide”. But this is a mistake! Table 2 represents properties of rocks!!!
3. Authors say that toppling deformation bottom boundary is represented in fig 7. But there are no toppling deformation bottom boundary in fig 7.
4. Authors say that set of joints (J2) perpendicular to the rock layers were clearly visible, fi lled with mud, and formed a crack zone (Figure 8a). Ð’ut there is no "crack zone" in fig.8.
5. Some conclusions are trivial . (350-353).
6. There is a problem with the name of the table 3. It is not related to toppling intensity grading system. It is related to a composition of the monitoring system
7. It is not clear how the rainfall conditions were modeled in Flac 3D.
8.There are many tautologies in the text, especially in section 3.3
Author Response
Response to Reviewer 1 Comments
Dear Editor-in-Chief and Reviewers:
Thanks for your letter and for the reviewer(s)’ comments concerning our manuscript entitled “Gravitational Deformation and Reactivation Mechanism of a Fault-bounded Slope, Eastern Yanshan Mountains, China” (ID forests-2220463). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied the comments carefully and have made a correction which we hope meets with approval. The main corrections in the paper and the responses to the reviewer(s)’ comments are as follows:
Point 1: Table 1 in section 3 is called as “ Toppling intensity grading system of the Nandongzi landslide”. The table describes four zones: Down-slope zone, Overlapping zone, Highly toppled zone and Weakly toppled zone. But nothing was previously said in the text about the division into zones. The zoning information appears much lower, only in section 4.
Response 1: Thanks for your comments. According to your comments, I moved Table 1 from Section 3 to Section 4.2.4. The title is corrected to “Table 2. Toppling intensity grading system of the Nandongzi landslide”. In the table the degree of unloading is determined by the RQD index and the rock structure of the core. Through my revised and sincerely hope to achieve your satisfaction. The content as follows:
Point 2: Table 2 is called as “Toppling intensity grading system of the Nandongzi landslide”. But this is a mistake! Table 2 represents properties of rocks!!!
Response 2: Thanks for your valuable and thoughtful comments. According to your comments, the title of the original Table 2 is corrected to “Table 1. Physical and mechanical parameters of rock and soil mass”. The content as follows:
Point 3: Authors say that toppling deformation bottom boundary is represented in fig 7. But there are no toppling deformation bottom boundary in fig 7.
Response 3: Thanks for your valuable and thoughtful comments. According to your comments, fig 7 has been modified. Toppling deformation bottom boundary is visible in the six point of the legend. The content as follows:
Figure 7. Stratigraphy from the geotechnical boreholes inside the landslide body and photos of the
principal rock types detected (A–F). Legend: 1 fault zone (photo A); 2 landslide mass (photo B); 3
sliding surface (photo C); 4 fully-weathered to strongly-weathered siltstone interbedded with shale
(photos D and E); 5 medium-weathering siltstone interbedded with shale (photo F); and 6 toppling
deformation bottom boundary.
Point 4: Authors say that set of joints (J2) perpendicular to the rock layers were clearly visible, fi lled with mud, and formed a crack zone (Figure 8a). Ð’ut there is no "crack zone" in fig.8.
Response 4: Thanks for your valuable and thoughtful comments. According to your comments, fig 8a has been modified. The "Crush zone" in Figure 8a has been modified to "Crack zone". The content as follows:
Figure 8. Core photographs of B09 borehole. (a) Down-slope overlapping zone. (b) Highly toppledzone. (c) Weakly toppled zone. (d) Original stratigraphic zone. (e) Stratigraphy from the B09 geotechnical borehole carried out inside the landslide body.
Point 5: Some conclusions are trivial.(350-353)
Response 5: Thanks for your valuable and thoughtful comments. Due to the short monitoring time, it is difficult to draw accurate conclusions on the development trend of slope deformation under different rainy seasons. Therefore, this paragraph is deleted in compliance with the reviewer's comments. Through my revised and sincerely hope to achieve your satisfaction.
Line 390-394
Point 6: There is a problem with the name of the table 3. It is not related to toppling intensity grading system. It is related to a composition of the monitoring system
Response 6: Thanks for your valuable and thoughtful comments. The title of the Table 3 is corrected to “ Table 3. Borehole characteristics and related types of installed monitors”. The content as follows:
Point 7: It is not clear how the rainfall conditions were modeled in Flac 3D.
Response 7: Thanks for your valuable and thoughtful comments. I used Flac3D to calculate the slope depths affected by rainfall under various onditions. Laboratory tests were used to obtain rock and soil mass physical and mechanical parameters under rainfall conditions. In the rainfall condition, the parameters were assigned to the model for calculation. In this paper, the numerical simulation study is not perfect, and only consider the deformation of slope under static water condition. The deformation of slope under hydrodynamic conditions will be further studied. Through my revised and sincerely hope to achieve your satisfaction.
Point 8: There are many tautologies in the text, especially in section 3.3
Response 8: Thanks for your valuable and thoughtful comments. According to your comments, the author has simplified section 3.3. Through my revised and sincerely hope to achieve your satisfaction. The content as follows:
Line:113-128
The monitoring equipment comprised two profiles. A total of four monitors, including three inclinometer monitors and one GNSS monitor, were deployed on the A-A’ profile. Five monitors, including three inclinometers and two GNSS monitors, were deployed on the B-B’ profile.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
This paper presents an interesting study regarding the gravitational deformation and reactivation mechanism of the Nandongzi landslide that occurred in the Yanshan region of North China.
The introduction of the manuscript provides a detailed overview of the background theoretical framework with adequate literature citations to provide a sound scientific justification for the study which is well-structured while illustrating the various data and topics.
The objectives of the study are well-framed and the description of the methods section is satisfactory except in some places where there is no useful information on data and bibliography.
The results are very interesting and are properly described in the discussions. In my opinion, the paper needs just minor revision. Some recommendations and suggestions regarding the manuscript, figures, and tables are included as pdf comments in the attached proof paper.
Comments for author File: Comments.pdf
Author Response
Response to Reviewer 2 Comments
Dear Editor-in-Chief and Reviewers:
Thanks for your letter and for the reviewer(s)’ comments concerning our manuscript entitled “Gravitational Deformation and Reactivation Mechanism of a Fault-bounded Slope, Eastern Yanshan Mountains, China” (ID forests-2220463). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our research. We have studied the comments carefully and have made a correction which we hope meets with approval. The main corrections in the paper and the responses to the reviewer(s)’ comments are as follows:
Point 1: You should provide bibliographic references about regional settings and site-specific geological setting.
Response 1: Thanks for your comments. According to your comments, I provide Guo Zhangzi Sheet K50E020020 1/50,000 Regional Geological Survey Report as a reference. The content as follows:
Line: 57-59
The Changzhougou Formation(Chc2) was composed mainly of quartz sandstone, siltstone and shale with a total thickness of 470.98 m and a single layer thickness of 0.5–30 cm approximately (Figure 1a)[31].
Point 2: In this section there is no description of the main outcropping lithologies (at least around the study area) and the corresponding reference to Figure 1a
Response 2: Thanks for your valuable and thoughtful comments. I supplemented the description of the main outcropping lithologies around the study area. The corresponding reference figure 1a is supplemented. The content as follows:
Line: 55-59
The main strata exposed in the study area are the Section II of Changzhougou Formation(Chc2) of the Changchengian Period. The Changzhougou Formation(Chc2) was composed mainly of quartz sandstone, siltstone and shale with a total thickness of 470.98 m and a single layer thickness of 0.5–30 cm approximately (Figure 1a)[31].
Point 3: indciare anche qui drilling o rimandare alal figura. comunque forse è meglio spsotare questa conclusione/risultato
Response 3: Thanks for your valuable and thoughtful comments. I referred to Guo Zhangzi Sheet K50E020020 1/50,000 Regional Geological Survey Report and rewrote the description of the fault with the data obtained from field investigations and cores. The content as follows:
Line: 72-77
Due to the structural compression of the Nanlaodong Fault, structural compression fracture zones formed on both sides of the fault. The fracture zones consist by fault gouge, quartz sandstone and cataclasite with total thickness of 30 m [31].
Point 4: Missing the corresponding reference to Figure 1b, I suppose。
Response 4: Thanks for your valuable and thoughtful comments. According to your comments, I have supplemented the corresponding reference to Figure 1b. The content as follows:
Line:84-85
The Nandongzi landslide was located on a convex bank slope(Figure 1b).
Point 5: Is it an original geological map or is it derived from the analysis of data and previous studies? where appropriate, insert the bibliography of the thematic maps used and the reference studies
Response 5: Thanks for your valuable and thoughtful comments. I provide Guo Zhangzi Sheet K50E020020 1/50,000 Regional Geological Survey Report as a reference. The content as follows:
Figure 1. (a) Geological setting of study area[31]. ……
Point 6: By whom was it made?
Response 6: Thanks for your valuable and thoughtful comments. I provide Guo Zhangzi Sheet K50E020020 1/50,000 Regional Geological Survey Report as a reference. The content as follows:
Line:97-98
Geological and stratigraphic data were obtained from a regional geological survey conducted in 2000[31].
Point 7: Better move table 1 in 4.2.4.
Response 7: Thanks for your comments. According to your comments, the position of the original Table 1 in section 3 to section 4.2.4. The title is corrected to “Table 2. Toppling intensity grading system of the Nandongzi landslide”. The content as follows:
Line:100-102
It comprised drilling 11 boreholes to depths of 18.4–67.4 m, six of which were equipped with inclinometer casings (Figure 2).
Point 8: Please indicate the fault line and eliminate this red line at the base of the landslide in Fig 2. Add blue line to legend.
Response 8: Thanks for your valuable and thoughtful comments. According to your comments, fig 2 has been modified. The content as follows:
Figure 2. Geomorphological map of Nandongzi landslides (1:1000 scale). Legend: 1) landslide scarp; 2) the boundary of toppling deformation rock mass; 3) the boundary of landslide mass; 4) deep large tension crack; 5) deformation zones; 6) Nandongzi fault; 7) boreholes; 8) deep inclinometers; 9) Global navigation satellite system (GNSS) monitors; 10) weather sensor; 11) track of geological cross sections; 12) slide direction; 13) the attitude of the rock layers and 14) seasonal current
Point 9: How much has increased the deformation of the cracks?
Response 9: Thanks for your comments. According to your comments, I added crack deformation increment description. The content as follows:
Line:164-166
In March 2018, local villagers noticed that the deformation of cracks had increased from 5-10cm to 20-30cm(Figure 4b)
Point 10: Without the references in the figure, this sentence is not very clear. indicate the sides of the slope.
Response 10: Thanks for your comments. According to your comments, I rephrased this sentence. The content as follows:
Line:174-176
The left boundary of the landslide expanded to the south approximately 130m(Figure 4d).
Point 11: Have you detected using traditional methods?What kind of statistical analysis?
Response 11: Thanks for your comments. According to your comments, I added the detected and statistical analysis methods. The content as follows:
Line:179-184
Nearly 200 sets of joint attitudes were collected through compass measurement. Based on the measurement results, the author used corresponding stereographs at different positions to statistical analysis the joint attitudes and mapped the geological sketch of slope surface excavation for Nandongzi landslide(Figure 5b)
Point 12: Please rephrase the sentence more clearly. Maybe, adding some details on the reference to the figure.
Response 12: Thanks for your comments. According to your comments, I rephrased the sentence and modified the Fig5. The content as follows:
Line:192-196
It can be seen in Figure 5f-h, located at the second step of the slope, that the dip angle of the rock layer (J1) decreases significantly from north to south. From the north to the middle of the slope, the dip angle of J1 decreases from 65°(Figure 5f) to 37°(Figure 5g). Finally, the dip angle is nearly horizontal on the south of the slope(Figure 5h). This phenomenon indicates that the rock layer has obvious toppling deformation(Figure 5b).
Figure 5. Rock outcrops and corresponding stereographs at different positions (equal area, upperhemisphere). (a)Overall view of landslide and outcrop locations of a typical joint. (b) Geological sketch of slope surface excavation for Nandongzi landslide. (c) Highly toppled rock masses at the back scarp.(d) Horizontal rock masses exposed by the wide tension crack in the middle of the slope.(e) Highly toppled rock masses at the landslide surface. (f) Steeply dipping rock layers in the downstream slope. (g) Moderately toppled rock layers at the landslide surface. (h) Highly toppled rock layers at the landslide surface.
Point 13: Please rephrase the sentence more clearly.
Response 13: Thanks for your comments. According to your comments, I rephrased the sentence. The content as follows:
Line:210-212
The strongly toppling deformed rock mass with gentle dip angle.
Point 14: According?
Response 14: Thanks for your comments. According to your comments, I changed the word "Combined with" to "according to". The content as follows:
Line:215-216
According to the field survey, the Nanlaodong Fault formed the right boundary of the landslide.
Point 15: These data are derived from direct or indirect laboratory analysis, I suppose. Please indicate how they were obtained.
Response 15: Thanks for your comments. According to your comments, the data of fault are dierived from field investigation. I rephrased the sentence about the fault. I apologize for the misunderstanding brought to the reviewer. Through my revised and sincerely hope to achieve your satisfaction. The content as follows:
Line:228-234
The author excavated a trial trench at the third step of the fault zone. The internal structure and composition of the fault zone were investigated and measured. In the trial trench, it can be seen that the rock structure of the fault zone was broken(Figure 6d). The rock mass consisted of massive-fractured gray-white quartz sandstone with sharp angularity and grain sizes ranging from 5–30 cm. The soil comprised gray-white clay minerals with a high degree of weathering(Figure 6e). Figure 6f shows quartz sandstone on the left bank of the river valley opposite the Nandongzi landslide. The rock structure was relatively intact with a low degree of weathering. At different locations on the same fault, the rock quality of the slope was obviously different (Figure 6d,f).
Figure 6. Outcrop locations of the Nanlaodong Fault. (a) Historical aerial image of the Nanlaodong Fault. (b) Distribution of fault zone in Nandongzi landslide. (c) Phenomenon of tectonic extrusion in the downstream gully. Rock structures in the (d-e) tip and (f) middle of the Nanlaodong Fault.
Point 16: Please indicate depth and related boreholes.
Response 16: Thanks for your comments. According to your comments, I indicate depth and related boreholes in the landslide shallow area. The content as follows:
Line: 259-260
In borehole B09 0-13.8m, the rock layers were flat with a dip angle of less than 23°.
Point 17: Have you tried yellow instead of white for better contrast of the dip? And it's not clear how this angle was measured.
Response 17: Thanks for your comments. In field investigation, I used a compass to measure the dip angle of the rock layers in core. According to your comments, I modified the color of the dip. The content as follows:
Line: 258-259
The author used a compass to measure the dip angle of the rock layers in the core.
Figure 8. Core photographs of B09 borehole. (a) Down-slope overlapping zone. (b) Highly toppled zone. (c) Weakly toppled zone. (d) Original stratigraphic zone. (e) Stratigraphy from the B09 geotechnical borehole carried out inside the landslide body.
Point 18: It would be appropriate to indicate and describe in the best and in detail the data and assumptions. as well as captions as already indicated. for example, how this surface was defined?. And the fig 9 missing description 1 to 14 in caption.
Response 18: Thanks for your comments. In Fig 9, we used 231 helicopter-borne images from June 4, 2020, and obtained elevation data of the slope based on the "structure-motion" method of photogrammetry. The front edge and back edge of landslide were obtained through field investigation. Based on the core, we determined the location of multiple toppling deformation boundaries and sliding surface in each borehole. The author used smooth curves to connect and establish the various surfaces.I apologize for the misunderstanding brought to the reviewer. Through my revised and sincerely hope to achieve your satisfaction. The content as follows:
Figure 9. The slope structure of Nandongzi landslide: geological cross section along profiles. (a) A–A’ and (b) B–B’ shown in Fig.3. Legend: 1) Quaternary alluvial-pluvial deposit; 2) down-slope overlapping zone; 3) highly toppled zone; 4) weakly toppled zone; 5) undeformed siltstone interbed- ded with shale; 6) undeformed quartz sandstone ; 7) sliding surface; 8) down-slope overlapping zone boundary; 9) highly toppled zone boundary; 10) weakly toppled zone boundary; 11) weakly weathered boundary; 12) borehole and borehole ID; 13) Nanlaodong Fault; and 14) inclinometer and inclinometer ID
Point 19: Is it possible to see a comparison between these data (indicating representative sectors) in a table?
Response 19: Thanks for your comments. I had investigated the cracks on May 16, 2020 and August 26, 2020, and selected four representative cracks near the Gnss monitors. The vertical deformations of the cracks and Gnss monitors were compared in the same time period (Table 4). The content as follows:
Line:348-354
The author investigated the cracks on May 16, 2020 and August 26, 2020. In the field investigation, the author found that it is difficult to accurately measure the horizontal deformation of cracks. Therefore, typical cracks were selected to measure the vertical deformation increments. The measurement results were compared with the vertical deformation increments from GNSS monitors at the same period (Table 4). The location and ID of typical cracks are shown in Figure 10. The results of the above monitoring data analysis were consistent with the results of the surface crack investigation of the Nandongzi landslide
Point 20: Please add more about this concept describing related features and giving the reference time interval of rainfall, and average value and trend with respect to the normal conditions of the area.
Response 20: Thanks for your comments. According to your comments, I added the multi-year average rainfall and the time of rainfall concentration in the study area, and further analyzed the deformation monitoring curve with the rainfall distribution time. The content as follows:
Line:374-378
The multi-year average precipitation in the study area is 529.1 mm, and June to August is the most concentrated period of rainfall each year. From 3-6 in Figure 11b,c, it is obvious that the monitoring curves of deep deforamtion increase steeply in July and August each year, and the monitoring curves are flat in the remaining time.
Figure 11. Monitoring data representing the temporal evolution of Nandongzi landslide from July 20, 2020 to February 10, 2022. (a) Location of monitors on ortho-image. (b) Vertical displacements, horizontal displacements, and cumulative displacements of GNSS monitors with daily rainfall precipitation of Nandongzi landslide. The two boxes in the figure show the displacement sharply increased in the rainfall intensive period. (c) and (d) Cumulative displacement of inclinometer monitors with daily rainfall precipitation along profile A-A’ and B-B’, respectively.
Point 21: What is the meaning of regional geological survey data? Are there references in the text?
Response 21: Thanks for your comments. According to your comments, I provide Guo Zhangzi Sheet K50E020020 1/50,000 Regional Geological Survey Report as a reference. The content as follows:
Line: 410-411
According to the field investigation results and regional geological survey data[31], the Nanlaodong Fault extends from west to east to the fifth step of the Nandongzi landslide.
Point 22: Please insert in the figure a legend describing the symbols and reticulate patterns for lithology
Response 22: Thanks for your comments. According to your comments, I added a legend describing the symbols and reticulate patterns for lithology in Figure 13.
The content as follows:
Figure 13. Toppling failure process of Nandongzi landslide. (a) Location of the profile. (b) Slope structure before the formation of the Nanlaodong Fault. (c) Initial topography of the slope before the formation of the river valley. (d) Initial deformation stage. (e) compression and bending stage. (f-g) Toppling and overlapping stage.
Author Response File: Author Response.pdf
