Heliyon 9 (2023) e13852 Available online 18 February 2023 2405-8440/© 2023 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Research article Geophysical and numerical stability analysis of landslide incident Adamu Beyene a, * , Narobika Tesema b , Fekadu Fufa c , Damtew Tsige a a Department of Civil Engineering, Jimma Institute of Technology, Jimma University, Ethiopia b Department of Civil Engineering, Ambo University, Ethiopia c Department of Water Supply and Environmental Engineering, Jimma Institute of Technology, Jimma University, Ethiopia A R T I C L E INFO Keywords: Landslide Slope stability Morgenstern-Price method Geophysical investigation ABSTRACT Landslide is known for its precarious impact on environment, resources and human life. Recently, landslide has occurred in Lalisa village, Jimma Zone, Ethiopia which harshly caused damage to life and property. The incident resulted in perilous damage of about 27 ha of accessible land. This study hence particularly aimed at investigating the root cause of the incident and analyzing safety of the sliding slope so that the applicable remedial actions can be proposed. Geophysical analysis without soil structure disturbance was adopted to investigate the vertical soil profle, morpho- logical stratifcation, location and alignment of discontinuity planes. Stability analysis by using Limit Equilibrium method was carried out for both normal and worst conditions to rate safety of the failing slope. Lithology of the site is characterized by highly weathered and fractured rock units exhibiting a signifcant variability over a little horizontal distance and depth. The stratig- raphy also constitutes loose soil near the surface and saturated layer ranging from depth of 10 m to 25 m. The slope failure occurred at the site is of deep by its type that origin of its slip plane extends up to a depth of 12 m from the surface. Furthermore, factor of safety of the slope along the failed zone fell below 1.5 with the maximum value of 1.303 for the normal condition. The conducted investigation also indicated that the detachment and propagation of the sliding mass develops much faster with rise in soil moisture content whereas it categorically remains mild during dry seasons. Hence, the driving agent for the occurrence and propagation of the landslide incident was rainfall infltration and the existence of weak saturated zone at the stated depth. 1. Introduction Landslides represent the directly gravity-driven component of soil or rock mass, ranging in size from individual rocks falling to whole mountainsides collapsing [1]. Landslides commonly happen in areas characterized with rugged topography where ground displacement is of random and fast which makes the condition so tough to fully control and prevent. But mitigation measures to lessen the resulting impact can possibly be taken [2]. According to M.T. Daniel et al. [2], the infuencing aspects of land slide include slope gradient, ground saturation and land cover in addition to some geological features (degree and depth of weathering, soil type, type and structure of rock). As studied by A. Nemcok, J. Pasek and J. Rybar [3], the main agents of landslide occurrence in vulnerable areas are geomor- phological, geological and hydrological features of the areas. However, A. O. Oliva-Gonzalez et al. [1] pointed out that in sloppy landscapes the landslide incident does not necessarily emanate only from the critical combination of geomorphological, geological and * Corresponding author. E-mail address: adamubeyene2014@gmail.com (A. Beyene). Contents lists available at ScienceDirect Heliyon journal homepage: www.cell.com/heliyon https://doi.org/10.1016/j.heliyon.2023.e13852 Received 22 January 2022; Received in revised form 4 February 2023; Accepted 13 February 2023