Integration of Geophysical and Geotechnical Methods for Road Route Characterization: the AddisrnAbaba-Awash New Detour Road at Lake Beseka: Main Ethiopian Rift, Metehara Area.rnTibebu G/MichaelrnAddis Ababa University, 2014rnAdequate knowledge supported by proper investigation of the sub-surface structure condition is arnvital task for effective assessment and control of weakening of road morphology. The presentrnresearch study was carried out to characterize the general suitability of the proposed route corridorrnby an integrated geophysical and geotechnical survey.rnThis research mainly focused on carry out detailed mapping of geological structures, providerninformation on the subsurface sequence, competence and with a view to extracting geo-engineeringrninformation in order to understand the basic impact and interaction of the cracks and its implicationrnon the newly constructed detour road and to evolve the possible remedial measures for the likelyrnengineering geological problems. The survey was aimed at imaging the shallow subsurface with arnview to evaluate the inferred geological Structures and competency of the shallow formation asrnfoundation materials.rnGeotechnically, in order to assess the general suitability of the construction material for selectedrnsegments of the subgrade and embankment, samples were collected and tested for grain sizerndistribution, Atterburg limits, swelling potential, California bearing ratio and in-situ densityrndetermination at the site. In general the construction material for the new road is slightly non plasticrnin nature, gap graded but good CBR. Thus, it is anticipated that this may result in to highrndeformability, segregation which may lead to instability. Also, the construction materials containrnmore fine materials than the desired percentage.rnGeophysical technique involving Electrical imaging and magnetic methods were applied and therndata were processed, analyzed and interpreted. Two to three subsurface layers were delineatedrnwithin the study area. The first of these is a topsoil of loose sand, peat and/or clay. This layer is inrngood correlation with the soil layers in geotechnical test pit logs. The existence of loose sand andrnsilty clay at the top surface is capable of being inimical to road structures. The subsurface layers uprnto the depth of 2m are mechanically unstable owing to weak, saturated horizons with low resistancernvalue, which may not serve as good foundation materials. In all survey lines, three to four majorrnsubsurface geological structures possibly of fissures/fractures are delineated up to the depth of 65mrnwhich aids the saline Lake water easily invade the road so that the susceptible to deformation .rnHence, Geophysical and geotechnical tests showed good agreement.rnFrom overall assessment, the problem of geologic structures, unsuitable subgrade materials andrnpoor grain size distributions of the subsoil, the engineering structures which may be crossed thernsection, are not prolong for required designed life owing to high traffic load. Therefore, in additionrnto tectonic activity of the area, the presence of low penetrative resistance, low resistivity saturatedrnsandy clay and weathered ignimbrites in the study area is identified as the cause of cracking andrnsinking of road in this area. On the basis of this, shallow subgrade foundation may not be possiblernin the study area unless adequate soil treatment is done; otherwise shifting to a competent soil andrnrock section area to depth of pronounced thickness of subgrade materials with less frequency ofrngeological structures is recommended to northern part from the current route line near the peripheryrnof the lake. This would transfer loads of such highway to a stratum of high bearing capacity even ifrnthe cost of excavation to the geometric design level is too high.