Slope Stability Assessment for Mana Begna-Lemlem Bereha Road,Northwestern Ethiopia

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Addis Ababa University


The present study was conducted on Mana Begna -Lemlem Bereha road which located in Fincha valley at about 318km northwest of Addis Ababa. This road connects Fincha sugar factory and northwestern parts of the country with Addis Ababa. From the present field observation, the area has slope stability problems and it require detailed slope stability studies to protect failure of structures and probable loss of life because of the slope instability problems. The main objective of the present study was to assess the stability of the slope along the section of Mana Begna-Lemlem Bereha road using Slope Stability Probability Classification (SSPC) system, Stereographic analysis, limit equilibrium analysis and SLIDE software. For the present study, an empirical and analytical approaches for data analysis and interpretation were used. Based on the field observation, three rock and one colluvium slopes were identified for further analysis. The slope probability stability analysis of rock slopes were made by SSPC system. Later, factor of safety for the selected slope section that satisfy the kinematic condition was determined using limit equilibrium analysis. The factor of safety of the rock slopes having a planar mode of failure was analyzed by the Modified technique of plane failure analysis of Sharma, (1995) and the rock slope with wedge mode of failure is analyzed by stereographic methods. For the stability analysis of colluvium slopes, SLIDE software were used that supports both deterministic and probabilistic approaches. The results of SSPC orientation independent stability indicates that slope section one and three have greater than 95% of probability to be stable, rock slope sections two has <5% probability of stability. The result of factor of safety by stereographic methods shows that slope section one has 1.36. According to plane failure analysis, rock slope sections two has factor of safety less than one under various conditions. Therefore, slope section two is unstable under anticipated adverse conditions. The results of colluvium slope shows that colluvium slope section was more affected by water saturation conditions. Finally, the remedial measures such as removal of unstable rock, making benches for rock slope and for colluvium slope an appropriate measures such as surface drains, horizontal drainage and retaining wall with appropriate water path were recommended.



Slope Stability Assessment, Mana, Begna-Lemlem Bereha, Road, Northwestern Ethiopia