Slope Stability and Sensitivity Analysis Based on Monitoring Data: a Case of Colluvial Slope Failure in the Abay Gorge, Central Ethiopia.
| dc.contributor.advisor | Geremew, Zemenu (PhD) | |
| dc.contributor.author | Manaye, Mihret | |
| dc.date.accessioned | 2019-07-29T08:46:57Z | |
| dc.date.accessioned | 2023-11-09T14:10:15Z | |
| dc.date.available | 2019-07-29T08:46:57Z | |
| dc.date.available | 2023-11-09T14:10:15Z | |
| dc.date.issued | 2018-05-04 | |
| dc.description.abstract | Evaluation of stability and sensitivity of recurrent landslides involving colluvium materials resting on gentle topographic slope has been carried out along multiple profiles in a landslide zone. The aim is to attempt integrating multiple profile stability analysis into semi- 3D stability model by weighting the factors of safety obtained in the 2D case with the cross-sectional area the above the slip surface of each profile. The 2D and semi- 3D models were implemented in Microsoft Excel spread sheet program using the simplified Janbu‟s method. The selected landslide area is located in the Abay Gorge between the towns of Gohatsion and Dejen, on the northern side of the Gorge. In total, 6 profiles which were aligned approximately parallel to the axis of the landslide from head to toe were evaluated. As the materials are colluvial and deep seated the depth to the slip surface, based on monitoring wells installed in the site, were used to back calculate shear strength parameters using stability charts of Janbu. The back analysis gave residual effective shear strength parameters of (5.7 KPa, 12.60) for profile 8; (5.2 KPa, 11.60) for profile 9; (3.3 KPa, 11.90) for profile 10; (0 KPa, 11.60) for profile 11; (3.6 KPa, 110) for profile 14; (1.7 KPa, 12.20) for profile 15 and (0.3 KPa, 11.80) for profile 16. The Simplified Janbu‟s method of 2D stability analysis at conditions of back analysed shear strength values and the determined water level from site investigation for each profile gave 2D factors of safety as: 1.94, 1.37, 0.84, 1.03, 0.73, 1.06 and 1.08 for profiles: 8, 9, 10, 11, 14, 15 and 16 respectively. The corresponding semi- 3D factors of safety computed by integrating the 2D factors of safety weighted by the respective cross-sectional area was 1.01. The influence on stability was assessed based on the sensitivity of the 2D and semi- 3D factors of safety to the independent changes in value of the shear strength parameters and water level, one at a time. Accordingly three selected profiles in the 2D and all the profiles in the semi- 3D cases showed marked sensitivity to changes in friction angle while the factors of safety had lowest sensitivity to the changes in cohesion. The sensitivity to changes in level of water gave intermediate change in both 2D and semi- 3D factors of safety. The low effect of change in cohesion on the factors of safety might be due to the progressive nature of the landslide. Although simplified and inexpensive methods to analyse the slope stability in semi- 3D approach have been attempted the expected results are not conclusive for various reasons v among which are mixed success with back analysis from slip surface location, and uncertainty in the continuity of the slip surface. Unexpected lower value of the 3D factors of safety might be hence improved by considering solutions to the determination of shear strength parameters and also ascertain continuity of the analysed landslide throughout the model. | en_US |
| dc.identifier.uri | http://10.90.10.223:4000/handle/123456789/18684 | |
| dc.language.iso | en | en_US |
| dc.publisher | Addis Ababa University | en_US |
| dc.subject | Slope Stability | en_US |
| dc.subject | Sensitivity Analysis Based on Monitoring Data | en_US |
| dc.subject | Abay Gorge | en_US |
| dc.subject | Central Ethiopia | en_US |
| dc.title | Slope Stability and Sensitivity Analysis Based on Monitoring Data: a Case of Colluvial Slope Failure in the Abay Gorge, Central Ethiopia. | en_US |
| dc.type | Thesis | en_US |