SCHOOL OF GRADUATE STUDIES FACULTY OF TECHNOLOGY ...

1.4 Lithologic Units and Soils
Residual fine soils, like clays and silt-clays, developed on basaltic bedrock mainly
represent the soil in Bahir Dar area. These soils are of two main types. The first type is
red clay soil the color of which is the result of reduction of magnetic minerals. These
soils widely occur in the northern part of the town, along the lakeshore at the central part
of the town [15].
The second type includes the dark and dark brown soil which mainly occupies the area
south and south west of the town.
Two rock units cover the area of Bahir Dar. The older being Tertiary Ashange Group
volcanics which is Paleocene Oligocene in age and Alkaline Olivine Basalt in genetics. It
covers the southeastern part of the lakeshore and eastern part of the city. The second and
the younger part is the Quaternary Volcanic Product. This volcanic product covers much
of the southern Tana basin and out crops in most part of the city of Bahir Dar [7].
1.5 Brief Review of Previous Works.
Some researches have been conducted on the area in the previous years. Especially an
M.Sc thesis done by Delelegn Alemu (2004) [7 ], and Getaneh Biru (2005) [8], have
relevance to expansive soils of the area. The works mainly focused on classifying the soil
and investigating its engineering characteristics.
1.6 Difference between the Recent Study and the Previous Works
- In the recent study, areas not included in the mentioned works are considered.
- Inter-relationship between the index properties and relationship between the index
property and Swelling characteristics is examined.
- Some new parameters (not used in the mentioned works), which could describe
the relationship better are employed.
- Predictive equations, which help in estimating the Swelling Pressure of the area,
are developed.
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