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