Geoscience Reference
In-Depth Information
Chapter 6
Slope Stability Model and Landslide
Susceptibility Using Geo-technical
Properties of Soil
Abstract The present study deals with the assessment of geo-technical parameters
i.e. surface inclination (
⊝
), soil depth (z), cohesion (c), angle of internal friction (
φ
),
soil saturation index (m), soil density (
ʳ
w
) and to construct
1D (one dimensional) Slope stability model for preparing the slope instability map
under dry, semi-saturated and saturated condition of the landslide prone small hilly
Shivkhola Watershed of Darjeeling Himalaya. To determine the spatial distribution
of slope instability in the watershed, safety factor value for 50 different locations
were being estimated and with the help of GIS tools. The probability or the chances
of landslide phenomena in each class of slope instability maps were extracted by
means of frequency ratio (FR) which shows that the probability/chances of land-
slide events could be expected as very high in the high to very high landslide
susceptibility area and vice versa in all three conditions. The analysis of slope
instability under three conditions also suggested that there was an aerial expansion
of very high landslide susceptibility in saturated condition in comparison to dry and
semi-saturated condition. This aerial expansion was the outcome of complete sat-
uration and reduction of shearing strength of the slope materials above the failure
plane surface. Finally, an accuracy assessment was made by ground truth verifi-
ʳ
s
) and density of water (
-
cation of the existing landslide locations where the classi
cation accuracy for dry,
semi-saturated and saturated conditions was 93.86, 94.58 and 85.44 % respectively.
Keywords Slope stability model
RS and GIS
Landslide susceptibility
Safety
factor (FS)
Frequency ratio (FR)
Accuracy assessment
6.1 Introduction
Slope instability resulted from complex geological setting combined with various
geomorphological, hydrological and geo-technical factors such as slope, relief,
aspect, rainfall, drainage, upslope contributing area, cohesion, angle of internal
friction, wet soil density, depth of the soil, shear stress, shear strength etc. But, the
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