New Conceptual Model of Large-Scale Landslide

The Second Global Summit of Research Institutes for Disaster Risk Reduction Development of a Research Road Map for the Next Decade March 19-20, 2015

Reported by Chjeng Lun, Shieh Director, Disaster Prevention Research Center National Cheng Kung University

National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background To review historical disasters from 1950, LSL & MSD occur frequently. Case Study                 

     09 11 12 1950 60 70 80 90 1999 2000 01 04 05 07 08 10 Idea

溫葛妮樂颱畢禮風琳莉颱恩賀風 Chi 伯象颱桃神風納芝敏莉艾督海利馬利棠聖莎颱卡帕辛風玫莫樂芭基拉凡克瑪梅克那南姬比蘇瑪拉都

- Saola Parma Megi 颱颱風風 Chi 颱颱風颱風風颱颱風颱風颱風風 Morakot Nanmadol 颱颱風風 Fanapi Experiment Earthquake ( ( ( ( ( ( ( ( ( ( (

typhoon typhoon

( ( ( ( typhoon typhoon ) ) ) ) ) ) ) ) ) 53 76 87 96 00 01) 01 04 05 05 07)

Lynn t Herb typhoonHerb Billie typhoon Billie Aere Winnie Winnie Typhoon Haitang typhoon Nari Masha typhoon Toraji Sepat

typhoon ) ) 63 04 08) 08) Modelized

Gloria Mindulle Kalmaegi Sinlaku

typhoon

typhoon yphoon

typhoon typhoon

typhoon

typhoon Solution Xangsane typhoon

typhoon

Comparison

Conclusion Flooding Disaster Sediment Disaster LSL & MSD -2- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Typhoon Morakot Case Study • The storm turned into a typhoon on Aug. 4. • Rainfall started on Aug. 6. Idea • The eye of the typhoon left Taiwan from Taoyuan at 14:00 on Aug. 8. • The rainfall continued until Aug. 10. Experiment

Modelized

Solution

Comparison

Conclusion

-3- • Path of the center of Typhoon Morakot National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Disasters of Typhoon Morakot Case Study  Alisan Station  Long duration (91 hours) Idea  High intensity (123 mm/hour)  Large accumulated rainfall depth (3000 mm-72 hour) Experiment  Broad extent (one-fifth of Taiwan was covered) Modelized

• Sediment-related disasters in the mountain area located within the Solution range of precipitation > 1,000mm Comparison • Inundation area located at the

downstream of rainfall center in Conclusion the plain area -4- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

The relationship between accumulative rainfall and duration of catastrophic typhoons Case Study

Alisan Station Idea

Experiment

Modelized

Solution

Comparison

Conclusion

-5- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study

Idea

Experiment

Modelized

Solution

Comparison

Conclusion • Shieh, 2012 -6- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background The scale and type of the disaster increasing with the frequent appearance of extreme weather Case Study

Idea

Experiment

Modelized

Solution

Comparison

Conclusion

-7- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Large-scale landslide and compound disaster become a new challenge Case Study

• Area：202 ha Depth：80 meter Volume： 24 million m3 Idea

Experiment

Modelized

Solution

Comparison

Before Typhoon Morakot in Hsiaolin After Typhoon Morakot in Conclusion Village Hsiaolin Village (FORMOSAT-2) (FORMOSAT-2) -8- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study

Idea

Experiment

Modelized

Solution

Comparison

Conclusion

-9- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background LESSONS FROM THE DISASTER OF HSIAOLIN VILLAGE

Case Study • Compound Disaster, included shallow landslide, debris flow, flooding, large-scale landslide, natural dam break, Idea occurred in Hsiaolin village Experiment • The main disaster is caused by large-scale landslide. Modelized

Solution

Mitigation Strategies of Large-scale Landslide Disaster Comparison in Taiwan Conclusion

-10- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

IDEA FOR MITIGATION STRATEGIES OF L.S.L. Case Study (6Ws1H)

Idea  Where  Potential Area Experiment  What  Risk analysis (Influence Area)  Why  On-site monitoring Modelized

 When  Forecast and Warning System Solution   Who Evacuation Plan Comparison  How  Training, Drills, Education Conclusion

-11- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background On-site monitoring Forecast and Warning System Case Study

Idea

Experiment

Modelized

Solution

All the monitor result to setup the warning Comparison system, such as rainfall, groundwater level, surface deformation. Conclusion How to combine all the result together? -12- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

• To Review Landslide cases in Case Study

typhoon Morakot, 2009 布唐布納斯溪 1399.8mm • Group A is classified as new born landslide, Idea and group B include enlarge case and A combine case B 1123.9mm Experiment • New Born Case 萬山

 Cumulative rainfall >1,000 mm Modelized  After rainfall peak  near the turning point of accumulative Solution rainfall B A • Enlarge & Combine case Comparison  Cumulative rainfall is about 300- 500 mm Conclusion  Before rainfall peak -13- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study

Idea

Case Study of Large-scale Landslide Experiment

Modelized in Taiwan Solution

Definition of Large-scale Landslide Comparison Area > 10 ha Depth > 10 m Conclusion 4 3 Volume > 10 m -14- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

• Fast-moving landslide was caused by Case Study typhoon. Idea • Hsiaolin Village, Kaohsiung County in

2009. Experiment

• Time：August/06-10 (Typhoon Morakot) Modelized • Area of landslide：202 ha • Depth of landslide：80 m Solution • Slope： ° Comparison • Movementퟐퟐ Distance： 2000 m • Accumulative Rainfall：2583 mm Conclusion • Loose soil mass • With the imprint of groundwater -15- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Fast-moving landslide was caused by typhoon Case Study • Taimali River, Taitung County in 2009

Idea

• Time：August/06-10 (Typhoon Morakot) Experiment • Area of landslide：290 ha

• Depth of landslide：200 m Modelized • Slope： °

• Movementퟐퟐ Distance： 1000 m Solution • Accumulative Rainfall：1400 mm • Loose soil mass Comparison • With the imprint of groundwater Conclusion

-16- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Slow-moving landslide was caused by rainfall Case Study • Lushan landslide, Nantou since 1994

Idea

Experiment

Modelized

• Area of landslide：30 ha Solution • Depth of landslide：~100 m • Slope： ° Comparison

• Mass movementퟐퟐ • With the imprint of groundwater Conclusion

廬山地滑監測及後續治理規劃，黎明工程，2003 -17- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Slow-moving landslide was caused by rainfall Case Study • Li-San landslide, Taichung, since 1990

Idea

Experiment

Modelized

Solution • Area of landslide：230 ha • Depth of landslide：~50 m Comparison • Slope： °

• Movementퟐퟐ Distance：800 m Conclusion • With the imprint of groundwater 中華水土保持學報，颱風降雨期間梨山地滑區邊坡穩定性之數值評估，2008 -18- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Similarity of F.M.L and S.M.L. Case Study Shallow Landslide Large-scale Landslide Large-Scale Landslide (fast-moving landslide) (slow-moving landslide) (fast-moving landslide) Idea

Experiment

LIMI, 2003 Modelized The Experimental Forest, NTU(2012 yr.) Lushan landslide Hsiaolin Village(2009 yr.) Occurrence: 4 days Solution Occurrence: < 2 days(Typhoon Saola) Occurrence: For decades (Typhoon Morakot) without the groundwater layer with the imprint of groundwater with the imprint of groundwater

  Comparison Slope= 22 ~ 29 Slope = 24 ~ 26 Slope= 26     φ ≈ 25 φr ≈ 22 ~ 27 φ ≈ 21 ~ 25 r Conclusion i = 30 ~ 35 mm/hr(2005~6 yr.) ip = 99.5 mm/hr p ip =103 mm/hr P =1132 mm P = 820 mm (2006 yr) P = 258m3m -19- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Difference of F.M.L. and S.M.L. Case Study

Idea S.M.L F.M.L Experiment

Modelized

Solution

Comparison

Conclusion

-20- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Safety Factor = Case Study 푅 퐹퐹 DRFSD−=−(1 ) = Net퐷 force acting on sliding block =Ma D: Driving Force D dFS R: Resistance Force Idea ⇒(1 −FS ) = a , where 1 −= FS ∆ t M dt M: Mass of sliding block D dFS ⇒=at ∆ Experiment M dt dFS ⇒∝a dt Modelized

Solution ∆t dFS ∆t Comparison dt

Conclusion

-21- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

• The flow velocity of infiltration and groundwater is usually small, therefore, Case Study what’s reason causes the rapid decreasing in F.S.?

• We are interesting in what kinds of interaction between infiltration and Idea groundwater will trigger sudden failure or creeping landslide. Experiment

Modelized

Solution

Comparison

Conclusion

-22- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case I：Air escape from bottom Case III： Air escape from top Case Study z z 0.04 m Air Flow z Idea z0 0 Water Water z zG G Infiltration Layer Infiltration Layer Experiment zh zh Seepage 0.85 m Seepage Modelized Cavity Layer Cavity Layer Air Flow z zGW GW Solution Saturated Zone Saturated Zone x x Comparison

Scale Pore water pressure gauge Conclusion

Experiment Wsc : weight  -23- measure data  pwb : porewater pressure National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Case I: Air escape from bottom p w Case Study

Idea pt

Experiment

Modelized

Solution

Comparison

c+−{(1 n )γ L + Sn γ h( t ) − p ( t )} tanϕθ cos S.F.= ss w w Conclusion {(1−+n )γγss L Sn w h( t )} sin θ  where, ϕθ=25 ; = 30 ;c = 0. -24- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Anticipation of change in Case II: Groundwater upwelling pore water pressure (Illustration) Case Study

pt Idea

pw Experiment

Modelized

Anticipation of change in S.F. Solution Elevation controlling of groundwater Comparison

Conclusion Scale Pore water pressure gauge -25- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Case III: Air escape from top pw Case Study

Idea

pt Experiment

Modelized

Solution

Comparison

c+−{(1 n )γ L + Sn γ h( t ) − p ( t )} tanϕθ cos Conclusion S.F.= ss w w {(1−+n )γγss L Sn w h( t )} sin θ where, ϕθ=25 ; = 30 ;c = 0. -26- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Develop the theory from physical phenomenon Case Study ∂nSρ w +∇⋅ ρ nS wwv=0 Idea Equation of ∂t mass conservation ∂−nS(1 ) ρ a +∇⋅nS(1 − )ρ v= 0 ∂t aa Experiment

Dvw Modelized nSρρw= nS wg++ ∇⋅( − p ww If) Dt Interaction among the constituents Equation of Dva Solution momentum conservation nS(1− )ρρa = nS (1 − )ag + ∇⋅( − p aa If) + Dt fwsa++= ff0 Dv (1−nn )ρρs = (1 − )gf + ∇⋅σ * + Comparison ssDt ss m Conclusion Equation of state pa V= RT M -27- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Convert the 3-D governing equation into 1-D. Case Study

• Interaction among the constituents in 1-D Idea -the momentum supplies(interactions) can be divided into two parts Experiment f buoy: caused by the normal pressure in the constituents surface rel f : the drag force due to the relative velocity tangential to the constituents surface Modelized

f w fs fa    Solution

buoy nS∂∂pp n(1− S ) buoy nS ∂∂ppnS(1− ) nS(1− ) ∂∂pp− =−+ww=−−wa +− buoy awnS(1 ) fnw (1 ) fns (1 ) (1 n ) fna =(1−− ) nz∂∂ n z nz∂∂ n z nz∂∂ nz ∂ ∂ rel piw rel ∂∂ppiw ia rel pia Comparison fw = − nS f= nS +− n(1 S ) fa =−− nS(1 ) ∂z s ∂∂zz ∂z

Conclusion

-28- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background • Governing equation in 1-D form Case Study ∂∂ (nSρρw) + ( nSww u ) = 0 Equation of ∂∂tz Idea mass conservation ∂∂ {nS(1−+) ρρa} { nSu( 10 −) aa} = ∂∂tz Experiment

Duw ∂∂pw p iw nSρρww=−−+ nS g nS  Modelized Dt ∂∂z z Du ∂∂p p ∂p nS(1− ) ρρa =−− nSgnSSn(1 ) + ( −−) a −−(1 S) w − n(1 − S) ia Equation of aaDt ∂∂z z ∂z Solution momentum conservation Du ∂∂p p ∂ p  ∂p ∂ p  (1−n )ρρs =−− (1n ) g −s + Sniw −−(1 n) w  +−(1 S) nia −−(1 n) a  ssDt ∂∂z z ∂ z  ∂z ∂ z  Comparison

m Equation of state p zA= RT Conclusion a M National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Case I: Air escape from bottom

Case Study

Idea

Experiment

Modelized

Solution

Comparison pt

ps Conclusion

pw -30- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background Case II: Groundwater upwelling Case Study pw

Idea

Experiment

Modelized

Solution

pt Comparison pw

Conclusion ps -31- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case III: Air escape from top Case Study pw

Idea

Experiment

Modelized

Solution

Comparison pt p w Conclusion ps -32- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study

Idea

Experiment

Conclusion Modelized

Solution

Comparison

Conclusion

-33- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study •This model is a pilot study of LSL warning Idea system in Taiwan . More field data are Experiment necessary before it is used. Modelized •The moment of infiltration front touch with Solution groundwater will induce fast-moving LSL. Comparison

Conclusion

-34- National Cheng Kung University, The Department of Hydraulic and Ocean Engineering, TAIWAN Background

Case Study Don’t Touch !! Idea

Experiment

Modelized

Solution

Comparison

Conclusion

-35-