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Geoelectrical, mineralogical and geotechnical investigations was conducted to determine factors responsible for pavement failure in Abakaliki-Obubra road in Ebonyi State, Southeastern Nigeria. Six Vertical electrical sounding (VES) investigation of deeper section of the study area show that the area is underlain by four layers; top soil, sandy-clay, silty shale and clay with resistivity range of 32.0-201.6Ωm, 22.6-450.6Ωm, 15.9-95.1Ωm and 19.0-78.9Ωm respectively with KH, Q, HK, KK, H curve types respectively. The Optimum Moisture Content (OMC) of the sub-grade ranged from 13% to 21%. While those of the sub-base ranged from 8.8% to15%. The strength are far less than the minimum required value. The Maximum dry density (MDD) values for subgrade and subbase ranged from 1.53g/cm3 to 1.81g/cm3 and 1.59g/cm3 to1.89g/cm3 respectively. The amount of materials passing 0.075mm sieve for subgrade varied from 20% to 94% and 20% to 56% for the subgrade materials. The Plasticity Index (PI) of the
sub-grade generally ranged from 8% to 30% and 6% to 35% for the subbase. The Liquid limit (LL) for subgrade and subbase ranged from 22% to 62% and 30% to 62% respectively. The X-ray diffraction results revealed that the study area was composed of
a significant clay mineral montmorillonite. It was concluded that low MDD, the class of subsoils namely A-7-5, A-7-6(clayey soils), Poor drainage and the presence of montmorillonite maybe responsible for the cause of failure experienced in the study
area. The soils are unsuitable for the road construction, requiring the necessity for stabilization during the road's reconstruction and rehabilitation.