Reconstruction of landslide model from ERT, geotechnical, and field data, Nargeschal landslide, Iran

Abstract

Landslides are natural hazards that cause severe casualties and financial losses. There are various methods used to analyze landslides; among these, geotechnical and geophysical methods are widely used due to their accuracy and low cost, respectively. In this study, 2D electrical resistivity tomography (ERT) surveys, geotechnical, and field data are used to define the subsurface structure and the geometry of the Nargeschal landslide. To determine the most appropriate array, ERT measurements were performed by Wenner-alpha (Wa), Wenner-Schlumberger (WS), and dipole-dipole (DD) arrays. Furthermore, the relationship between electrical resistivity with change in the degree of saturation and landslide hydrology was investigated by completing multiple surveys at the same location, at different times. Landslide 3D geometry and hydrology were identified by ERT results. Moreover, geotechnical data was used to investigate the Nargeschal landslide and to interpret the ERT pseudo sections. The data from boreholes were used to constrain the depth and consequently the resistivity range that characterize the basal slip surface of the landslide in the ERT pseudo sections. The results of geotechnical investigations indicated that the landslide material had moisture content very close to the plastic limit, with a higher clay fraction and low shear strength at the slip surface. Finally, it must be noted that the simultaneous use of the ERT survey, geotechnical methods, and field investigations led to a complete and accurate characterization of the Nargeschal landslide.