Geo-spatial Variability of Physiographic Parameters and Landslide Potentiality - Semi-quantitative Approaches for Landslide Assessment and Prediction - page 79

Fig. 2.12 Spatial distribution of granule (%)

silt show the higher plasticity and high to very high tensile strength and low
landslide potentiality. We can say that the major size fraction of the soil controls
various physical properties of soil such as tensile strength, volumetric expansion,
plastic condition, porosity, permeability and water retention capacity as well as the
rate of liquefaction of slope materials.
Soil samples from 12 locations of Paglajhora Sinking Zone, one of the major
landslide prone areas of Darjiling Himalaya, were being collected and tested in the
laboratory (GSI) to understand physical properties of soils related with slope
instability. The study envisages that the saturated soil density varies from 2.00 to
2.60 and dry soil density varies from 1.20 to 1.96 (Table 2.10 ). The variation of
saturated soil density is less which helps to liquefy the soils chemical properties and
make all the places more conducive to slope failure. Percentage of sand, silt and
clay are also distributed in at this place uniformly. The cohesion in the Paglajhora
Sinking zone is very less (<0.7) and friction angle ranges from 22 ° to 37 ° .