Abstract
Roads constructed along the mountainous terrains of Ethiopia are susceptible to landslides mostly during rainy season. Mekelle – Abi Adi road is one of the economically important road corridors that connects many towns with Mekelle city. However, the asphalt road segment is heavily affected by quasi-translational type of landslide which hinders traffic flow of the area. Vertical electrical sounding (VES) method was applied to investigate subsurface geology of the road failure along Mekelle – Abi-Adi asphalt road, northern Ethiopia. The geo-electric section result revealed that the shallow subsurface geology of the site is characterized by four distinct geological formations, from top to bottom are: shale, shale-limestone intercalation, limestone and shale-gypsum units. The subgrade of the failed road section is shale unit which is overlain by jointed sandstone unit. The sandstone unit serves as a recharge zone to the bottom shale layer by percolating water via sub-base fill materials which in turn blocks vertical percolation and promote seepage force to the overlying soil mass. Hence, the road failure in the study area seems to be caused due to the development of pore water pressure in the shale layer which soaked water during heavy rainfall. The recommended remedial method for the road failure is re-designing of the affected route from chainage 48 km+850 m to 49 km+250 m towards the northwest of the study area and excavates the top 6 m shale unit.
Highlights
Road transport sector is one of the most powerful instruments used to promote economic growth and poverty reduction (Fan and Rao, 2003)
Interpretation was made based on the integration of results from the vertical electrical sounding, geological traversing and secondary borehole log data from the two borehole wells drilled for drinking purpose
The landslide in the road section has occurred after the heavy rainfall in August 4, 2016
Summary
Road transport sector is one of the most powerful instruments used to promote economic growth and poverty reduction (Fan and Rao, 2003). Road networks in developing countries speed up the overall socio-economic development by providing vital communication links. Construction and maintenance of road and highway networks in the developing countries are often problematic, and have resulted to economic setbacks (Okogbue and Aghamelu, 2010). Stability and durability of road depends on the traffic load and the strength of pavement layers (Kiehl and Briegleb, 2011). Geotechnical problems of a road could critically influence on the design, performance, lifespan, construction cost and maintenance of roads. Geotechnical investigations are used to select and compare alternative routes for the road. An appropriate assessment of soil and rock characteristics is crucial in solving geological and Momona Ethiopian Journal of Science (MEJS),V13(1):134-146, 2021 ©CNCS, Mekelle University,ISSN:2220-184X
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