Geophysical Investigation and Management Plan of a Shallow Landslide along the NH-44 in Atharamura Hill, Tripura, India

In any effective landslide hazard mitigation plan, in-depth knowledge about the causes of instability is required. Consequently, it is essential to study geological, geotechnical, meteorological and anthropogenic factors that influence the landslide. For the present study a geophysical investigation has been carried out on a large landslide, on the slopes of Tertiary siltstones, mudstones, shales and sandstones at Atharamura Hill, Tripura. Different techniques have been used, including measurement of micro-slope using Total Station, clinometers and the LISCAD software for terrain modeling and determining the total volume of the material displaced and total area affected by landslides and analysis of soil properties to understand the present condition of the scarps. Results obtained through field investigation and laboratory testing revealed that the underlying cause of the slide could be (a) the adverse geological formation with unconsolidated sandy materials and occasional intersection of silt or clay layers, (b) the hydrological condition with continuous seepage through fractures, and (c) cutting of hill slopes for reconstructing and widening of the road (NH44). This latter anthropogenic influence has been triggered by an intense precipitation event during the monsoon season.