Hadush, Seged (PhD)Bantayeu, Uba2021-02-042023-11-112021-02-042023-11-112011-06http://etd.aau.edu.et/handle/12345678/24971In Ethiopia, so many researches were done on characterizing expansive soils of several towns But only a single study,done on Addis Ababa expansive soil, exists on the unsaturated shear strength behavior of expansive soils.The present study addresses examining the expansive soils in ArbaMinch–at own with a great portion of it sterrain covered by the same soil but not considered inprevious studies. A laboratory-testing program was planned and carried out on undisturbed soil samples taken from 10 different locations in the town for swelling pressure testing; and among these,one pit was allottedforunsaturatedshearstrengthstudy. Thelaboratorytestresultsrevealedthattheswellingpressurerangesfrom74.53to571.29kPa, SpecificGravityfrom2.63to2.80, PlasticityIndexfrom49to77%, ShrinkageIndexfrom81to117%andFreeSwellfrom94.0to165.0%The measured swelling pressures and the geotechnical parameters determined fromidentificationtestsareusedtoassessthevalidityofalreadydevelopedexpressionsbyvariousresearcherstothesiteunderstudyandnewmodels,thatrelateswellingpressurewithindexandphysicalproperties,aredevelopedusingSPSS16.0forwindowssoftware. Theresultsfromunsaturatedshearstrengthtestsperformedwitha50kNmodifieddoublewalltriaxialmachineonanundisturbedsamplesettingmatricsuctiontobe100kPa,150kPaand200kPaforaneffectiveconsolidationpressureof200kPahaveclearlyindicatedthesaturatedcasetoyieldsmallershearstrengththantheunsaturatedone.Themaximumdeviatorstressshowedtoincreasefrom107.61kPato174.35kPawithanincreaseinmatricsuctionbuttheshapeofthestress-straindiagramremainedidentical.en-USShear StrengthExpansive SoilsArbaminchThesis