Slope Stability Analysis on a Selected Slope Section along the Road Gohatsion – Dejen
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Date
2011-04
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Addis Ababa Universty
Abstract
Rainfall triggered landslides is a common problem in many areas; along road cuts, hilly and
mountainous regions of the highlands of Ethiopia. In the Blue Nile gorge, landslide is a
common problem for last many years, especially during the rainy seasons. Slope instability
problems in the form of rock fall, landslide and complex disturbances are the common
events in the area on the sides of the main road from Gohatsion to Dejen. Detailed slope
stability studies along this road will give opportunity to deal with the different mode of
failure separately and to provide the best remedial measures for the different slope sections
independently to protect failure of structures and loss of life because of the slope instability
problems.
For the present study a detailed slope stability analysis was carried out for a critical slope
section which falls 15 km short of Dejen town about 215km from Addis Ababa. For the
study, both primary and secondary data were used. The primary data was collected from
the field work measurements and the observations. The secondary data used for the
present slope stability analysis were collected from the GSE and JiCA teams working on the
landslide problem along the road from Gohatsion to Dejen. Sensitivity analysis was also
performed to estimate the shear strength parameters (cohesion and internal friction angle)
for the detail slope stability analysis.
The deterministic slope stability analysis approach was followed to perform the detailed
slope stability analysis of the selected slope section in the present study. In the present
study factor of safety for the selected slope section was determined for the different
conditions using SARC software. In addition, SLOPE/W software was also used to determine
the factor of safety for the present condition under static state.
The results of the slope stability analysis clearly indicate that the slope section is stable only
for the dry condition under static state with a FOS of 1.28. For the other conditions, both
under static and dynamic state, the slope section will be unstable with a FOS less than 1.0.
The factor of safety for the dynamic state for worst condition is even less than 0.5. Thus,
finally based on the slope stability analysis findings for existing and anticipated worst
conditions suitable remedial measures were worked out.
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Keywords
Legedadi & Dire Reservoir Catchment