Assessment and Mitigation of Slope Stability Hazards Along Kombolcha- Desse Road, Northern Ethiopia
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Date
2013-06
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Addis Ababa Universty
Abstract
The Kombolcha to Desse road, linking Addis Ababa with Northern Ethiopia towns traverses
through one of the most difficult mountainous ranges in Ethiopia. Slope instability problems
in the form of rock fall, rotational failure of colluvial material and debris slides are the
common events in the area on the sides of the main road. The presence of loose
unconsolidated materials (colluvial materials), highly weathered and fractured basalt rocks
high relief, steep natural slopes, nature of geologic formations exposed along the road
section, poor drainage conditions, occurrence of high seasonal rains, and seismically active
nature of the region created favorable condition for slope instability in the area. Thus,
keeping in mind all above points the present study was conceived to study in detail the slope
stability condition of the area. It was realized that detailed slope stability studies along this
road section are very necessary to identify critical slopes and to provide the best remedial
measures to minimize the slope instability problems which frequently disrupt and endanger
the traffic movement on this important road.
For the present study based on the field manifestation of instability two most critical slope
sections were identified for detailed slope stability analysis. The deterministic slope stability
analysis approach was followed to perform the detailed slope stability analysis of the selected
slope sections. Factor of safety for the selected slope sections was determined for the
different anticipated conditions (i.e., static and dynamic with varied water saturations) using
Slope/W and Slide software. Both static and seismic slope stability analysis was carried out
and factor of safety was deduced for each anticipated conditions. In general, detailed slope
stability analysis of the two critical slope sections reveals that for only static dry condition
both the slopes sections would be stable. However, for the rest anticipated conditions defined
by static and dynamic situations with varied water saturations both critical slope sections
would be unstable.
Moreover, the causes of slope instability in the study area are governed by different factors;
therefore integrated approaches of remedial measures are more appropriate to mitigate the
possible slope instability in the study area. Depending on site condition and slope stability
analysis result four types of suitable preventive and remedial measures are recommended
namely; proper managements of drainages, retaining structures, gabions, and managing
steeply cut slopes.
Key words: Slope stability analysis, Sensitivity analysis, Factor of safety, Remedial
measures, Static and Dynamic condition.
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Keywords
Slope stability analysis, Sensitivity analysis, Factor of safety, Remedial measures, Static and Dynamic condition