“Slope Stability Assessment of Recently Constructed Railway Embankment along Lagos-Ibadan Rail Line, Nigeria”

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Slope Stability Assessment of Recently Constructed Railway Embankment along Lagos-Ibadan Rail Line, Nigeria.

Abstract:

This research focuses on the stability evaluation of a newly constructed railway embankment along the Lagos-Ibadan rail line. Soil samples were obtained from four locations: KM75+500, KM90+500, KM105+500, and KM116+500, at depths ranging from 0m to 5.5m and 5.5m to 10m. These samples were subjected to various laboratory tests, including particle size analysis, Atterberg limits, standard Proctor, and direct shear tests.

The assessment of slope stability was conducted for the high-filled embankments at KM75+500, KM90+500, KM105+500, and KM116+500. Geotechnical parameters derived from the direct shear test were used as inputs for slope/W software, which aided in the slope stability assessment.

Results revealed that the fill materials for the embankments from 0m to 5.5m were categorized as A-2-6 (clayey soil) subgroup in the AASHTO classification system, consisting of 78% sand and 17% fine particles, and were considered average soil according to International Union of Railways specifications. However, the subgrade materials from 5.5m to 10m, comprising 51% sand and 49% fines, were classified as A-6 (clay soil), with a high liquid limit of 41% and plastic index of 19% at KM116+500. These materials were deemed poor soil according to railway specifications, necessitating stabilization.

The factor of safety of the embankments, as per the U.S. Army Corps of Engineers criteria, indicated that the slope was stable at KM75+500, KM90+500, and KM105+500, with a factor of safety greater than 1.3. However, the slope at KM116+500 was found to be unstable, as the factor of safety was less than 1.3. Additionally, a trend of increasing factor of safety with decreasing embankment height was observed.

Based on these findings, it is recommended that slope protection and soil treatment measures be implemented for the embankments at KM116+500 to enhance their stability.

Slope Stability Assessment of Recently Constructed Railway Embankment along Lagos-Ibadan Rail Line, Nigeria.

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