Behavior of Addis Ababa Light Rail Transit Embankments under Seasonal Changes in Suction

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Addis Ababa University


This research paper presents research on the behavior of selected embankment sections along the Addis Ababa Light Rail Transit (LRT) experiencing matric suction variation due to seasonal changes. In this study, an extended Mohr-Coulomb soil model in the MIDAS GTX NS software has been utilized to analyze the effect of precipitation on matric suction and by extension on slope stability and settlement prediction of a railway embankment along the North-South direction of the AALRT. The software implementation of the model was initially verified using an already published research on slope stability analysis of unsaturated soil. Climate data analysis has been conducted for a 40-year rainfall data acquired from the Ethiopian Meteorological Agency. Spatial and temporal simulation of matric suction variation has been carried out. The investigation's findings demonstrated that utilizing rainfall observations in the finite element analysis, it is possible to accurately anticipate how the matric suction distribution profile changes over time in an embankment. Results further indicate that as matric suction diminishes, stability is compromised, and settlement increases due to the upsurge in intensity, duration, and frequency of rainfall. The analysis's findings also indicate that one of the most crucial variables influencing rainfall infiltration for unsaturated slopes is rainfall intensity. It has also been made apparent that matric suction (and by extension slope stability and settlement) is highly affected by the location of ground water table. The factor of safety is amplified with raising depth of ground water table. Therefore, establishing the actual GWT is crucial in analysis and monitoring of actual embankments.



Embankment, Matric Suction, Settlement, Stability, Subgrade, Suction, SWCC