TECTONIC MAP OF INDONESIA AND THE PHILIPPINES
Australian Plate
Jawa
Papua
Kalimantan
Indian Oceanic Plate
Philippine Sea Plate
Caroline Plate
Eurasian Plate
MoluccaSulawesi
Bali
Asia
Banda Arc
90 E 140 E
Sumatra
The complex tectonic plates convergence
Indonesia as an active tectonic region
Water content – volume unit weight relationship
Expansive soil containing montmorillonite (5-7%) and haloysite (35-50%)
water content (%)
Vol
ume
unit
wei
ght
(gr/
cc)
x = in rainy seasono = in dry season
SLOPE INSTABILITY ZONING MAPPING OF LANDSLIDE HAZARDOUS AREA
FOR THE STABILIZATION SYSTEM (3991)
byProf. Febri Hirnawan
Faculty of Geological Sciences and EngineeringPadjadjaran University
Bandung - INDONESIA2010
Water content – internal friction angle relationship
ditto, the same soil mass
Inte
rnal
fric
tion
angl
e (o
)
water content (%)
x = in rainy seasono = in dry season
Earth-quake coeff.
Angle of slope (o)
Vege-tation
Depth of slip sur-face (m)
Length of slip sur-face (m)
Shear strength
(Ton)
Shear force (Ton)
Safety factor/stability
0.000.050.050.100.000.050.050.100.050.100.050.10
14.2614.2614.2614.2612.2612.2612.2612.2611.2611.2610.2610.26
NoNoYesNoNoYes
Yes*)Yes
Yes*)Yes*)YesYes
47.0027.5027.5019.5047.0027.5027.5019.5027.5019.5027.5019.50
450.224443.006443.047439.743452.917444.411444.403440.663445.042441.051445.661441.429
1.3871.2161.2161.0791.3791.1951.1971.0521.1841.0391.1681.020
1.3341.0711.0690.9221.2470.9780.9780.8240.9320.7770.8860.729
1.039/unstable1.136/critical1.139/critical1.171/critical1.106/critical1.222/critical1.224/critical1.276/stable1.271/stable1.338/stable1.319/stable1.399/stable
*) double vegetation density
Dry Season Rainy season
Slope stability affected by vegetation
Safety factor Fs
NOTE :
**) significant at α = 0.01LA-P+ is the most effective position of vegetation which raises largest Fs in both dry- and rainy seasons
water content (%)
ditto, the same soil mass
Coh
esio
n (k
g/cm
2 )
x = in rainy seasono = in dry season
Result of simulation of the effects of αhor, i, and Wveg on FS
Discussion & Conclusion • Effect of rain water on soils and slope stability : soil
strength deceases with increasing soil water content slope safety factor (F) decreases with increasing soil water content (w)
• Effect of vegetation on slope stability : slope safety factor (F) increases with both increasing weight of biomass on slope toe and decreasing biomass of slope summit
• Effect of eathquake loading on slope stability : slope safety factor (F) decreases with increasing earthquake coefficient (αhor)
• Simulation to stabilize critical slope stability conducted to stabilize slopes at earthquake loading condition at max αhor and densest rainy season using slope geometry modification and vegetation planted at maximal weight on toe part of slope and minimal weight on summit of slope to achieve F ≥ 1,25 (Long Term Deep Seated Stability) and F = 1 (Seismic or Pseudo-static Stability) as the design criteria.
THANK YOU VERY MUCH
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