Abstract:
Landslide is a natural disaster in which earth mass materials like rock, debris, or earth move
down a slope and cause damage to living things, as well as the natural environment. In 2020, the
landslide occurred in Chira town following heavy rainfall. As a result, Residential houses,
internal roads of the towns, pipelines, and natural environment were damaged following the land
subsidence of the study area. Therefore, this research aimed to conduct geotechnical conditions
and stability analysis of landslide occurred in Chira Town. The main objective of the study was
include investigation on geotechnical conditions and their role in landslide occurrence,
identification of the main triggering factors, slope stability analysis by using Plaxis 2D and Slide
software's, and propose remedial measures to safeguard future failure in the study area. To
achieve the objective of this study, experimental and analytical methods were conducted. To
determine subsurface condition, Geophysical test was conducted. Soil samples were taken from
the crest and toe of the affected and unaffected slope area at different depths and test on index
and engineering properties of soils was conducted following the ASTM procedure. Three slopes
were analysed by plaxis 2D and slide softwares on affected and unaffected slopes. Based on
laboratory tests and geophysical investigation, the soil types of the study area were dominated
by fine-grained soils (Clay &silt) and they initiate the occurrence of landslide since they are
weaker soil when contact with water. Rainfall is the major triggering factor and from prediction
rate of causal factors, the soil type, land use, elevation, distance to stream, slope, aspect and
curvature were a reason for the occurrence of Chira landslide by 22.03%, 18.89%, 15.75%,
15.46%, 10.87%, 9.7%, and 7.5% respectively. FS varied between 1.34 to 1.95 (by plaxis) and
1.35 to 1.93 (by slide) for affected slopes and 0.66 to 0.98 (by plaxis) and 0.67 to 0.97 (by slide)
in saturated and dry state respectively. Hence, they are considered as unstable slopes. FS for
unaffected slope varied between 1.83 to 3.18 (by plaxis) and 2.02 to 3.17 (by slide), which is
stable. The LE overstimate the FS from 5% - 20% over FE analysis in dry and partially
saturated conditions respectively. Groundwater increament decreases the FS by 42.45% -
50.75% (by plaxis) and 35.94% - 49.93% (by slide) software's. Surface drainage, planting
vetiver vegitation, and proper landuse management were the proposed remedial measures for
Chira town landslide.
