Shrink Swell Susceptibility Zonation Of Addis Ababa

The present study was carried out in Addis Ababa. The main objective of this study is to carry out shrink swell susceptibility mapping of Addis Ababa. rnClay soils are found in many parts of Ethiopia, especially southern, south eastern and south western part of Addis Ababa. Damages due to the shrink swell phenomenon has been frequently reported. rnSwell potential of such soil can be predicted by both direct and indirect methods. By combining direct and indirect methods of swell potential measurements that predict shrink–swell behavior, a susceptibility map has been established for Addis Ababa. This map shows sensitive areas toward shrink and swell phenomenon. rnThe adopted methodology has been modified from French Bureau of geological and mining research (BRGM) approach. This procedure allowed the identification and spatial variation of shrink swell potential of soil in the study area. Then, they were classified and rated based on their volume changing potential as per given standard. rnThe criterions used to establish susceptibility map are the lithological (plasticity and free swell), geotechnical (clay fraction and thickness of expansive soil) and mineralogical parameters. Each criterion and or parameters was rated, combined and sum together. This summation was divided by the number of the layers (plasticity index, free swell, clay fraction, lithological thickness and percentage of swelling mineral) to get the mean. rnFinally shrink swell susceptibility map has been produced based on the mean. The formations have been classified in to three classes and represented by tarragon green, yellow and red colors representing low, medium and high susceptibility to shrink swell respectively. rnThe shrink swell susceptibility map shows that 30% (159km2) of the study area has a ‘high shrink swell potential’, 38% (196km2) of the study area has ‘medium’ shrink swell potential. Whereas, the areas that account for ‘low shrink swell potential’ and ‘non clay or rock formations’ are 18% (96km2), 14% (76km2), respectively. Thus, the shrink swell susceptibility map can be used as a regulatory tool in land use and planning procedures.

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