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Geotechnical and environmental problems of the Niger delta

  • C. O. Okagbue
Article

Abstract

This paper examines the geotechnical and environmental problems arising from the peculiar characteristics (topography, geology, soil types including their properties and their areal distribution) of the Niger Delta area. The area is characterised by the widespread and irregular distribution of weak soils whose strength is further reduced by the presence of expansive clays. This causes foundation problems in roads, houses and embankments. Excavations are unstable because they are either made in very permeable sands which are subject to enormous seepage pressures or in weak, fat clays of low shear strength.

Environmental problems include flooding, poor water quality and excessive river bank erosion and recession. While the surface waters are very turbid due to high clay and silt content the ground waters are very acidic (pH 4.5–5.5) and contain high proportions of nitrates, ammonia and chlorides which contaminate aquifers especially in the coastal and central portions of the delta area. River bank failure and recession of up to 2 to 3 m occur annually and continue to pose an enormous threat to the villages along the river banks.

Keywords

Nigeria Niger Delta California Bearing Ratio Expansive Clay Alluvial Valley 

Problèmes géotechniques et d'environnement du delta du Niger

Résumé

Cet article examine les problèmes géotechniques et d'environnement provenant des caractéristiques particulières (topographie, géologie, types de sols en incluant leurs propriétés et leur répartition) de la région du delta du Niger. Cette région est caractérisée par une distribution étendue et irrégulière de sols «faibles» dont la résistance est de plus réduite par la présence d'argile expansive. Ceci est à l'origine de problèmes de fondation pour les routes, les habitations et les digues. Les excavations sont instables car elles sont faites soil dans les sables très perméables qui sont soumis à d'énormes pressions d'infiltration soit dans des argiles plastiques montrant une faible résistance au cisaillement.

Les problèmes liés à l'environnement incluent l'inondation, la pauvre qualité de l'eau, l'érosion et le recul excessif des berges des rivières. Alors que les eaux de surface sont très turbides en raison du taux élevé d'argile et de silt, les eaux des nappes sont très acides (pH 4.5–5.5) et contiennent de fortes proportions de nitrates, d'ammoniac et de chlorures qui contaminent les aquifères, en particulier dans les régions côtières et centrales du delta. Des reculs et destructions de berges des rivières (jusqu'à 2 à 3 m) se produisent chaque année et continuent à menacer grandement les villages situés sur leurs rives.

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Copyright information

© International Association of Engineering Geology 1989

Authors and Affiliations

  • C. O. Okagbue
    • 1
  1. 1.Department of GeologyUniversity of NigeriaNaukkaNigeria

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