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Preliminary geotechnical assessment of Nkari earth damsite, southeastern Nigeria

Authors: Esu, E.O., Ilori, A.O., Hambley, D.F.
Key words: Nkari, Akwa Ibom, Nigeria, damsite, Benue Trough, Imo Shale, heavily consolidated, expansive
Source: The International Journal of Geotechnical Engineering
Volume: 4
Issue: 3
Pages: 14
Date: 2010-07-01
DOI: 10.3328/IJGE.2010.04.03.371-384

This paper discusses the geotechnical investigations performed for a proposed earthfill dam at Nkari in the northeastern part of Akwa Ibom State in southeastern Nigeria. The geotechnical testing included soil classification, compaction, and hydraulic-conductivity determination, direct shear tests, uniaxial and triaxial compression tests, and bearing capacity (cone penetration) tests. The tests demonstrated that the local soils were silty (MH and OH under the USCS classification), with medium to high expansion potential, poor drainage characteristics (hydraulic conductivity less than 1.50 10-5 cm/sec), and compressive strength between 60 and 70 kPa. The shale at the site is heavily consolidated with an overconsolidation ratio (OCR) between 9.0 and 13.0. Despite the high potential for expansion of the soil when excavated, collapse of the soil upon loading by the dam is unlikely and settlement is likely to be minimal with maximum crest settlement estimated at 3.61cm. The site geology and the drainage characteristics of the soil at the site suggest a potentially watertight reservoir. Preliminary analyses indicate that the dam structure has adequate stability against sliding.



This paper was added to our catalog on Tuesday 24 August, 2010.

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