Slope Stability Assessment on A Critical Rock Slope Section Around Alem Ketema, North Shoa, Ethiopia
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Date
2018-05-02
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Addis Ababa University
Abstract
Slope Stability Assessment on a Critical Rock Slope Section around Alem Ketema, North Shoa, Ethiopia.
Dawit Asmare Manderso
Addis Ababa University, 2017
The present research was carried out in an area around Alem ketema town, North Showa, central Ethiopia; with a general objective of conducting a rock slope stability assessment on the selected natural rock slope sections. To achieve this objective, slope stability probability classification and geological strength index approaches were followed to determine the stability probability conditions of slope rock mass in the study area. These classification systems mainly depend on the primary data collected from field works. As a reason, systematic and extensive field work was conducted. However, secondary data was also required in order to characterize the general conditions of the study area and to have a deep understanding on the subject matter. In SSPC system, ratings for degree of weathering, intact rock strength, method of excavation, roughness condition and infill material were given according to standards.
The SSPC system uses three step classification systems (exposure rock mass, reference rock mass and slope rock mass). Following these steps, slope rock mass stability probability classifications have been carried out for 92 natural slope sections. The stability of slope rock mass were determined by two different approaches namely orientation dependent and orientation independent stability. Orientation dependent stability related to orientation of the discontinuities and characterized by toppling and sliding criteria, while orientation independent stability related to the strength of slope rock mass. Accordingly, overall assessment indicated that 80.4% of slope sections showed less than 5% stability probability, 10.9% of slope sections showed from 5 to 49%, 6.5% showed from 50 to 95% and the rest 2.2% of slope sections showed greater than 95% stability probability. According to GSI system, the slope rock mass quality obtained falls in to three classes; 63.1% of slope sections showed fair quality, 21.7% showed good quality and 15.2% showed poor quality. All these result were also compared with the visual stability assessment results. Moreover, different stability probability maps were produced for all assessment approaches. Finally, on the basis of findings of the present research, recommendations are forwarded.
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Keywords
Slope Stability Probability Classification (SSPC, Geological Strength Index (Gsi), Exposure Rock Mass (EMR), Reference Rock Mass (RRM), Slope Rock Mass (SRM), Orientation Dependent Failure and Orientation Independent Failure