A study on landslides and subsurface piping, facilitated by dykes, using vertical electrical sounding and δO18 and δH2 stable isotopes

A combination of vertical electrical sounding (VES) and delta O-18 and delta H-2 stable isotope geochemistry is used in this study to trace out the extension of a dyke and for deciphering the subsurface piping phenomena in a landslide-affected hamlet, Pasukadavu, in the Western Ghats of Kerala, India. VES was successful in extracting three to four different subsurface layers characterized by differing resistivity. Two VES sections were prepared from 24 different VES locations, each one for understanding the dyke extension and for delineating subsurface conduits. The dyke was characterized by high resistivity of 800-5000 Omega.m and shows varying thickness. In the second profile, the void zone, which is characteristic of piping, is delineated through a low resistivity zone (75 to 350 Omega.m). delta O-18 and delta H-2 stable isotopes collected along the second VES profile show the same chemistry, indicating that it is the same water which flows all along the VES profile 2. A four-stage conceptual model was developed to illustrate and narrate the sequence of development of the piping phenomena and landslide activity.