Determination of physical property of the soil helps in identification and classification
of soil which includes analysis of particle size distribution, Atterberg
limits, water content, specific gravity, phase determination and direct shear
test. Water plays an important role in triggering landslides and slope failures.
Increase of water content reduces the stability of slope. When the moisture
content exceeds plastic limits, the slope begins to deform. Three soil samples
are collected from the study area and the average bulk density, moisture content
and specific gravity are 1.577, 37.032 and 2.434 respectively. Atterberg
limit is the most distinctive properties of fine grained sediments and may be
used to distinguish silts from clays. Plastic limits (WP), liquid limit (WL),
shrinkage limit (WS) values of Nungbi Khunou are 26.236%, 48% and 9.4%
respectively. Plasticity index (IP), consistency index (IC) and liquidity index
(IL) value is 21.764%, 0.379%, and 60.623% respectively. From index properties
value, the soil is highly plastic, stiff and semi-solid in nature. The soil
sample falls under CI group in plasticity chart which indicates organic silt and
clay soil with medium compressibility and plasticity. Phase determination and
particle size distribution result in very high porosity and highly saturated soils
which are well graded in nature. Slope and aspect map are prepared from
DEM using ArcGIS. Slope is an important contributory factor to landslide,
and slope reported from the sampling area indicates gentle slope. Aspect refers
to the direction of the terrain faces which is influenced by component like
vegetation, settlement, agriculture, precipitation, wind etc. Factor of safety
(Fs) calculated from shear stress data is less than 1 indicating unstable slope.
From the above finding, the study area may result in sudden and unpredictable
failure due to volumetric changes in soil.