Assessment of Slope Stability Using Combined Probablistic and Deterministic Approach for Selected Sections Along Gohatsion Dejen Route, Blue Nile Gorge, Central Ethiopia
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Date
2013-06-05
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Addis Ababa University
Abstract
The present research study was conducted in the study area defined by Gohatsion and Dejen towns, in Abay Gorge, Central Ethiopia. The study area is about 185Kms north of Addis Ababa on the main road that connects Addis Ababa to Bahir Dar town. The study area witnesses severe problem of landslides during rainy seasons. Such slope failures in the area frequently hampered the safe functioning of the road, which is the important link between the Addis Ababa and the northern part of the country.
The main objective of the present research study was to evaluate the stability condition of selected critical slope sections by combined deterministic and probabilistic methods for existing and anticipated worst conditions to which the slopes would be subjected.
The general methodology followed includes; literature Review, collection of primary and secondary data, analysis of data by different graphical, empirical and analytical approaches through standard software, interpretation of results and finally based on the results recommendations were evolved. Based on the field manifestations of actual and potential instability, a total of four critical slope sections; two from failed colluvium section and two from rock slopes were identified for further analysis. Later, relevant data pertaining to various aspects related to geology, geomorphology, hydrogeology, climate etc. from both primary and secondary sources was collected. The stability analysis of colluvium slopes were made for the existing and anticipated worst conditions by utilizing SLIDE software that supports both deterministic and probabilistic approaches. Similarly, for rock slope having planar mode of failure ROCPLANE software that operate based on the principles of Modified Analytical Technique proposed by Sharma et al., (1995) and support both deterministic and probabilistic methods were also utilized for analysis.
The results from the present study in general indicates that the critical colluvium slope sections, investigated in the present study, would be unstable during anticipated adverse conditions and possibility of damage is unavoidable during the event of failure. The general characteristics of these slides with respect to the mass involved in large quantities, deep seated failure plane, groundwater conditions and progressive failure mode made it difficult to suggest and implement any techno-economic feasible remedial measures. Therefore, avoidance of these slope sections for any developmental activities would be more economic and safer option. The stability analysis carried out for rock slope section by deterministic and probabilistic approaches has revealed that the slope is stable and would be instable under anticipated adverse conditions. However, manifestation of instability of this slope section was observed during the field trip. Thus, stability analysis was made at slide block level. The deterministic and probabilistic analysis results suggest possibility of rock block failures during anticipated worst conditions. Thus, based on the general findings of the present research suitable recommendations have been forwarded.
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Assessment, Slope Stability Using Combined Probablistic, Deterministic Approach, Dejen Route, Blue Nile Gorge, Central Ethiopia