1. Non-catastrophic Hongtsaiping Landslide Induced by the 1999 Chi-Chi Earthquake in Central Taiwan Insights from Distinct Element Method
1Chia-Han Tseng (曾佳漢)
1Jyr-Ching Hu, 1Chao-Lung Tang, 2Yu-Chang Chan, 3Ming-Lang Lin, 4Jin-Fa Lee, 4Jheng-Yue Wei
1Department of Geosciences, National Taiwan University, Taipei, Taiwan
2Institute of Earth Sciences, Academia Sinica, Taipei, Taiwan
3Department of Civil Engineering, National Taiwan University, Taipei, Taiwan
4Central Geological Survey, Taipei, Taiwan

2. Introduction of the Hongtsaiping Landslide
Background
Results from various kinds of research
Distinct Element Method (DEM) applied to the Hongtsaiping Landslide
Reasons for use of the DEM
Results of 2D and 3D

3. INTRODUCTION

4. Faulting

5. Faulting Faults all around Taiwan island, 42 active faults
The Chi-Chi earthquake in 921
Red lines: active faults
(modified from CGS, 2000)

6. Landslide areas ‧ 9,272 landslides greater than
625 m2, total area of km2.
‧ellipse-shaped region, coinciding
with the trend of regional faults
Purple areas: landslides triggered by the 1999 Chi-Chi
earthquake
(Lee et al., 2000)

7. Landslide areas ‧ 9,272 landslides greater than
625 m2, total area of km2.
‧ellipse-shaped region, coinciding
with the trend of regional faults
‧Heavy rainfall due to typhoon
events
Purple areas: landslides triggered by the 1999 Chi-Chi earthquake
Yellow areas: landslides ( )
(Lee et al., 2000)

8. Jiufengershan
36 million m3 in volume

9. landslide triggered by the Chi-Chi earthquake
Tsaoling
• million m3 in
volume, the largest
landslide triggered by
the Chi-Chi earthquake

10. volume, non- catastrophic landslide reported after 3 days of the
Hongtsaiping
• million m3 in
volume, non-
catastrophic
landslide reported
after 3 days of the
Chi-Chi earthquake

11. Location of the Hongtsaiping area

14. Results from various kinds of research
Photogrammetry based on orthorectified aerial photographs
Maximum displacement
24.7 m
(modified from Lee et al., 2004)

15. Aerial Photogrammetry
1998/06
1999/12
2002/10
(Hongtsaiping)
(0.61 m/pixel)
overlapped image

16. Particle Image Velocimetry (PIV) Technique
Maximum displacement: 24 m

17. PIV technique II 3 main sliding areas defined of sliding A1 A2 B
(modified from Lo et al., 2006)
• Various directions
of sliding A1 A2 B

18. Borehole analysis 13 borehole sites Lithology of sliding mass defined
80 m in thickness
BH1
BH2
BH3
BH4
BH5
BH6
BH7
BH8
BH12
BH13
BH9
BH10
BH11
Colluvium with sandstone grain
Colluvium with Shale matrix

19. Nature of colluvium
(Ke, 2006)

20. Nature of ancient landslide
Strata and sliding plan curved by geological structure
Ancient landslide occurred due to 4 earthquakes in between August 1916 and January 1917.
(Huang et al., 2006)

21. DISTINCT ELEMENT METHOD (DEM)

22. Reasons for use of the Distinct Element Method
Colluvium as the material of the sliding block of the Hongtsaiping landslide → a series of behavior of failure and movement can be applied to the Distinct Element Method.
Ancient and present landslides are large-scaled behavior of transformation which is one of features of the Distinct Element Method.

23. Particle Flow in Code 2 Dimension (PFC2D)
Tsaoling landslides, (Tang et al., 2009)

24. The Hongtsaiping landslide before the Chi-Chi earthquake
Pink line: Topography before the Chi-Chi earthquake
(Chang, 2007)

25. The landslide model triggered by the Chi-Chi earthquake
20 meters
Maximal displacement:
18 m
Movement duration:
160 seconds
(Chang, 2007)

26. 3D model building
According to borehole and the region of surface displacement data to make a reasonable model
40 x 40 m grid Digital Terrain Model (DTM)

28. Walls building of Hontsaiping landslide for Distinct Element Method model

29. Walls with balls Radius of balls in upper part is from 2 ~ 3.2 m
Radius of balls in lower part is from 1 ~ 1.2 m
Number of balls: 20,000

30. Hongtsaiping landslide Jiufengershan avalanche
Summary – comparison between Hongtsaiping landslide and Jiufengershan avalanche
Hongtsaiping landslide
Jiufengershan avalanche
Circular failure
Layered colluvium resulted from ancient landslide
Maximal 80 m in thickness
Friction coefficient of sliding surface is 0.24
F = 1.93 dropped to 0.94 when the Chi-Chi earthquake occurred.
Dip-slope slide
Intact strata
average thickness of 60 m
Friction coefficient of the surface of separation is 0.2

31. THANKS FOR YOUR ATTENTION

32. Electrical Resistivity Imaging Profile
Lower slope
Upper slope
(Huang et al., 2006)

33. Micro properties for PFC

34. Principal of Particle Flow Code
(PFC2D Manual, 2002)

35. Potyondy and Cundall (2004)
Type of contact for PFC
Mode of contact stiffness
Mode of bond
Mode of sliding
Potyondy and Cundall (2004)