rockfall in northern taiwan: mechanism, numerical...
TRANSCRIPT
The case study of Badouzihrockfall in northern Taiwan: mechanism, numerical simulation and hazard assessment
Ching-Fang Lee, Ting-Chi Tsao, Lun-Wei Wei, Wei-Kai Huang
Disaster Prevention Technology Research Center, Sinotech Engineering Consultants, INC., Taipei, Taiwan
June 2, 2016
13th CongressINTERPRAEVENT 2016KKL Lucerne, Switzerland
Outline
01
Introduction
02
Study area and
methodology
03
Investigation
and simulation
04
Conclusions
Introduction
01
Introduction01
Taiwan Swiss
Population 23 million 8 million
Highest Mt. 3,952 m 4,634 m
Annual Prec. 2,502 mm 1,537 mm
Introduction01
(source: NASA)
Introduction01 Rock fall
Debris flow
Landslide
Landslide
Introduction01
Rockfall events Alone Highway No.2
(1994~1996;2004~2013)
This event
(Event data from MOTC, Taiwan)
# of events
Highway No.2
Yi-Lan
New Taipei
Taipei City
Keelung
LEGEND
Introduction
About the rockfall disaster
The Badouzih rockfall was triggered by rainfall on August31st, 2013 in Keelung City in northern Taiwan.
The highest intensity rainfall of 94.5mm/h occurred, leadingto a rockfall disaster at 16:19 in which a passing car wasstuck on Provincial Highway No. 2
More in Wei et al. (2014), Engineering Geology, 183: 116-126.
The boulder had a weight of roughly 115 ton and dimensionsof 4.5 m × 4 m × 3.8 m; another roughly 235 ton boulderremains perched on the ridge.
01
GIS center, FCU
2013/08/31-9/1 - Keelung station
Time [hr]
10 12 14 16 18 20 22 24 2 4 6 8 10 12 14 16
pre
cip
ita
tio
n [
mm
]
0
20
40
60
80
100
120
effe
ctiv
e c
um
ula
tive
pre
cip
itatio
n [m
m]0
100
200
300
400
500
precipitation
effective cumulative precipitation
2013/09/01
occurrence of rockfall
(source: https://www.youtube.com/watch?v=8wWuH7MIeCA)
Introduction01
Badouzih rockfall
intensity 10yr 25yr 50yr 100yr 200yr
60 min 77.1 88.4 96.1 103.2 110.1
Imax=94.5mm/hr 50 yr rainfall intensity (96.1mm/hr)
duaration [min]
0 500 1000 1500 2000 2500
rain
fall
inte
nsity [
mm
/hr]
0
50
100
150
20010 yr
25 yr
50 yr
100 yr
200 yr
08/31 Rainfall
intensity-duration-frequency curve (IDF)
Introduction01
(source: United Daily News, Sep.3, 2013)
Study area and
methodology
02
Study area and methodology02
terrain production
unmanned aerial vehicle (UAV)
airborne and terrestrial LiDAR
DTM
field survey
geological drilling and material test
field investigation numerical simulation
RAMMS::ROCKFALL
failure mechanism hazard map
1 2 3
geological setting
02 Study area and methodology
Schmidt hammer test: rock strength=250~290kg/cm2
The study area consists mainly of calcareous massivesandstone belonging to the Taliao Formation (Tl) whichfeatures ridges and promontories along the northerncoast.
The attitude of the bedding plane is approximatelyN81°E/8°S and the attitude of slope surface at the sourcearea is about N70°W/35°N, forming an anaclinal slope.
Two interlocking joint sets: N 72°W/88°N (J1), N16°E/88°N (J2)
J2
J1
68K
8
8888
Investigation and
simulation
03
Investigation and simulation03
Boulder #2 remained on the hilltop (Sep., 2013)
Investigation and simulation03
rockfall trajectory on the cross-sectional profile.
123
3 1
J1
J2
Geological investigation
Investigation and simulation
Rockfall trajectory (Boulder #1)
03
12
main path : 1
path : N10o/E 2
toward north direction
1
2
UAV photo provided by GIS.FCU
UAV photo provided by GIS.FCU
Investigation and simulation03
toppling
sliding
rolling
falling
bouncing
1
2
3
4
5
1 2 3
4 5
UAV photo provided by GIS.FCU
Investigation and simulation
rockfall mechanism (Boulder #1) on the longitudinal profile.
03
UAV photo provided by GIS.FCU
Investigation and simulation03
Scenario 1 : Boulder 1 Scenario 2 : Boulder 2
parameter validation hazard map production
single rock multi-rocks
Parameter value sourceboulder size[m] 4.54 * 4.09 * 3.84 m in-situ measuring
elevation of source area [m] 119 in-situ measuringdensity [kg/m3] 2,650 experimental result
release point (x, y) (329028, 2781980) aerial image(TWD97)
initial rotational velocity (X, Y, Z) (rad/s) (0.3, 0.5, 0) video record
rock type Equant_1.3calculated by RAMMSrock mass [ton] 115.44
rock volume [m3] 42.75
Parameter of the boulder
Geologic parameters used in the RAMMS simulation (resolution of DEM: 5m)
No. terrain material friction reference
1 TI (S.S) colluvium 0.25 (soft) in-situ measuring
2 TI(S.S and Sh. interbedded) colluvium 0.25 (soft) in-situ measuring
3 Road and Fishery Harbor concrete 0.40 in-situ measuring
4Forest type Height [m] Drug [kg/s]
medium 1.5-3.0 1500 in-situ measuring
A
B
GIS center, FCU
Boulder #1- validation (the event in the study)
Boulder #2- prediction(remains on thehilltop)
Investigation and simulation03
03 Investigation and simulation
Scenario 1 : Boulder 1
(a) 3D rockfall trajectory
(b)the real rockfall trajectory on the aerial image
(c) Simulation trajectory in RAMMS
The result of numerical simulation RAMMS::ROCKFALL
UAV photo provided by GIS.FCU
03 Investigation and simulation
Horizontal distance (m)
0 20 40 60 80 100 120 140 160
Kin
etic
ene
rgy (K
J)
0
10x103
20x103
30x103
40x103
50x103
60x103
70x103
80x103
90x103
100x103
Ve
locity (
m/s
)0
10
20
30
40
Kinetic energy (Rocfall-Wei(2014))
Kinetic energy (RAMMS)
Velocity (Rocfall-Wei(2014))
Velocity (RAMMS)
Scenario 1 : Boulder 1 The comparison of Rocfall 2D and RAMMS:: Rockfall 3D
Velocity and kinetic energy:3D model are less than 2D model.
Difference in model: rock shape topographic model accuracy Forest drag
03 Investigation and simulation
Scenario 2 : Boulder 2
Parameter valueboulder size[m] 5.3 * 5.8 * 4.9 m
elevation of source area [m] 122density [kg/m3] 2,650
release point (x, y) (329028, 2781980)
initial rotational velocity (X, Y, Z) (rad/s) (0.3, 0.3, 0)
rock type Equant_1.2rock mass [ton] 234.44
rock volume [m3] 88.60Number of rocks 100
Parameter used for multi-boulder simulation
03 Investigation and simulation
Scenario 2 : Boulder 2
kinetic energy (KJ) – Q95% Boulder velocity (m/s) – Q95% jump height (m) – Q95%
02 Study area and methodology
Diagram of hazard levels as a function of probability and intensity (BUWAL, 1999)
2D Rockfall hazard map
O. Lateltin et al., Landslide risk management in Switzerland. Landslides (2005) 2: 313–320.
1-30 yr30-100 yr100-300 yr
G. B. Crosta, F. Agliardi. A methodology for physically based rockfall hazard assessment. Natural Hazards and Earth System Science, 2003, 3 (5), pp.407-422.
Crosta and Agliardi (2003)
Lateltin et al. (2005)
03 Investigation and simulation Scenario 2 : rockfall hazard map
Intensity criteria form Crosta and Agliardi 2003)Intensity criteria form Lateltin et al.(2005)
Conclusions
04
A good event documentation is vital to rockfall modelingcalibration, this case study shows how a well documented rockfallevent could contribute to numerical simulation.
RAMMS::ROCKFALL is able to integrate the detailed block shape,terrain material, and initial condition for modeling three-dimensional rockfall event. And the simulation shows good result.
For hazard mitigation, the hazard map which associated with rockmass strength assessment (frequency) and numerical simulation(intensity) around alpine region can help predicting future rockfalloccurrence.
Conclusions04
Conclusions04
Photo: Keelung City Government
What happened to Boulder #2 ??
Conclusions – UAV application 04
DJI-P3P
30 March, 2016 (resolution: 5cm)Badouzih harbor
UAV photo provided by Sinotech
[email protected]://dptrc.sinotech.org.tw
13th CongressINTERPRAEVENT 2016KKL Lucerne, Switzerland
Ting-Chi TSAODisaster Prevention Technology Research Center, Sinotech Engineering Consultants, INC.
Special thanks to RAMMS
team of WSL, for providing
the ROCKFALL model in the earlier stage of this study