Geotechnical and geological investigation of landslide in West Arsi Zone, Ethiopia

In 2018, a landslide occurred in Tullu Gola Peasant Association, West Arsi Zone, Oromia, Ethiopia. The landslide destroyed more than 15 ha of land, four dwelling houses, trees mixed with coffee, cultivated land, road, animals, grassland and a tiny spring, as well as disrupting socioeconomic operations. The purpose of this work was to investigate the causes of landslides employing geotechnical conditions and geophysical techniques. The specific parameters of the landslide investigation include rainfall conditions, soil type and composition, slope angles, gradient, groundwater table and geological and geomorphological conditions. To determine the subsurface condition of the area, a geophysical method was conducted. The numerical analysis of the slopes was done by finite-element methods. Both disturbed and undisturbed soil samples were taken from the top, right, left, and bottom of the slopes. The soil type of the study was dominated by fine-grained soils, and strength and other property tests proved that it contributed to the occurrence of landslides. Natural moisture content, permeability, consistency limits, shear strength and consolidation test results of the soil found in the area confirmed that the soil geotechnical properties increase the chance of occurrence of the landslide. The landslide was caused by a combination of circumstances, including the type of soil, high rainfall, deforestation and a number of streams that were nearby. The study area's landslide is also a result of the area's naturally unstable geology, height and slope steepness. The affected area's (the slope's top side) factor of safety was 0.62, whereas the unstable slope's (the slope's right side) factor of safety was 1. Applying proper slope drainage to lessen water penetration, soil grouting, planting trees and building gabion at the higher and lower ends are examples of corrective measures to mitigate the risk of landslides.

Automated summary

This article investigated the causes of a landslide that occurred in Tullu Gola Peasant Association, West Arsi Zone, Oromia, Ethiopia, using geotechnical conditions and geophysical techniques. The study found that the landslide was caused by a combination of circumstances, including soil type, high rainfall, deforestation, and nearby streams. Corrective measures to mitigate the risk of landslides, such as slope drainage, soil grouting, tree planting, and gabion construction, were suggested.