Study of substrata of a slope susceptible to landslide in hilly environment using a geophysical method in The Nilgiris, India

Abstract

Landslides are one of the prevailing threats to life that causes huge loss to the environment. Around 3.7 million km2 of the area is exposed to landslides globally and 820,000 km2 is at high risk for landslides in India. The major triggering factors of landslide in India are rainfall and earthquake. The Nilgiris district which is located in the south-western part of India is more prone to rainfall induced landslides. This study intends to calculate the depth of the slip surface on the slope (Lovedale area, The Nilgiris) in the event of a future landslide using Multichannel Analysis of Surface Waves (MASW). During November 2009 rainfall, a shallow landslide occurred at the toe of this particular slope. Hence, there are more probability for re-occurrence of landslide in the event of rainfall. The shear wave velocity (Vs) obtained from MASW was useful in understanding the variation of the sub-strata and predicting the depth of potential failure surface. The elastic moduli of the soil calculated using empirical relations and software, were compared and one reliable method was considered. The MASW results can be further used for analysing the stability of the slope, reactivation of landslides and landslide early warning system.