Abstract:
Slope failure emerges as one of the most serious issues in geotechnical work, leading to damage to engineering structures such as buildings, dams, roads, railways, and other associated structures. Roads are damaged by slope instability. Therefore, analyzing slope stability is essential for minimizing damage caused by slope failure. Recently, slope instability has occurred in the present research area. This study targeted to carry out assessments of the geotechnical properties and slope stability analysis of the road that connects the Wolaita Sodo-Gilgel Gibe III hydroelectric project. The main objective of this study was evaluation of geotechnical properties, causes of instability, and to recommend remedial measures for failed selected slope sections. In order to fulfill the objective of this investigation, numerical and experimental techniques were carried out. The experimental study was conducted by collecting soil samples from selected road for laboratory experiments in accordance with ASTM standards, including natural moisture content, specific gravity, Atterberg limits, grain size analysis, and shear strength tests. In order to find out their sliding potential, a total of seven samples from the most critical slope sections of the Wolaita Sodo-Gilgel Gibe Ⅲ road were studied. Based to the geotechnical analysis results, the soil contains 4%–35.41% fine, 48.2%–70.17% sand, and 11.15%–26.81% gravel. The soil samples were classified using the USCS and AASHTO with group symbols of SM, SW-SM, SW, and A-2-4 and A-2-6 respectively. Based on the direct shear test results, the cohesion and internal friction angle varied from 5.6–22.29 KN/m² and 22.30⁰–29⁰, respectively. In the present study, the safety factor was computed based on the FEM using PLAXIS 2D V 8.6 and the FDM using FLAC V 7 software packages. The factor of safety results shows the study area was unsafe except two sites, the remaining was safe (FOS > 1); due to a variety of factors influence the causes of slope instability, Such as the steepness of the slope, type of soil, and other geological factors. Therefore, in order to reduce the possibility of slope instability in the research region, integrated approaches to remedial actions are more appropriate. Depending on the site condition and analysis results, for site 3 the recommended engineering structures were perforated pipe and soil nailing. For site 2 and site 5, geogrids and retaining wall were suggested. For others, proper management of drainage and geometry modification was recommended for remedial measures.
