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Engineering soils mapping in the tropical terrain: The Ghana experience

  • Ayetey J. K. 
  • Frempong E. M. 
Article

Abstract

Laterites and other products of weathering in the tropics are an important source of material for highway construction. For any extensive use such as has happened over the past two decades when there has been a lot of development, rehabilitation and maintenance of roads throughout Ghana, it became necessary to evaluate and map these materials.

Research into laterites and lateritic soils and other problem soils of Africa has been undertaken. Highway materials evaluation and mapping in Ghana has also been undertaken.

This paper appraises the methodology used in the evaluation, highlights the fieldwork, including sampling processes and limits of extrapolation of point profiles for the development of line profiles leading to the preparation of two types of maps:
  1. (a)

    Area soils maps of selected areas;

     
  2. (b)

    General engineering soils maps of Ghana:

     
  1. i

    Laterite and lateritic soils maps.

     
  2. ii

    Saprolitic soils maps.

     

The quantitative evaluation is then undertaken using the map and various profiles, and problems encountered in doing this are discussed. Laboratory testing methods are discussed with problems, some of which are unique to the tropical situation, highlighted. The relevance of geology and soil forming factors to the prediction of occurrence and mapping of engineering soils is emphasized. The speed and economy inherent in the method is also shown.

Keywords

Parent Rock Lateritic Soil California Bearing Ratio Compaction Characteristic Compressional Wave Velocity 

Cartographie géotechnique en terrains tropicaux: L'expérience du Ghana

Résumé

Les latérites et autres produits de l'altération dans les régions tropicales sont une source importante de matériaux pour la construction routière. Pendant les deux dernières décennies l'extension et l'entretien du réseau routier se sont beaucoup développés au Ghana et il est apparu nécessaire d'évaluer et de cartographier ces matériaux. Des recherches sur les latérites, les sols latéritiques et autres sols “à problèmes” on été entreprises.

Cet article présente la méthodologie utilisée, mezt en exergue le travail de terrain, incluant les procédures d'échantillonnage évaluant les limites d'extrapolation qui conduisent à 2 types de cartes:
  1. (a)

    cartographie des sols dans des secteurs sélectionnés;

     
  2. (b)

    cartographie géotechnique globale des sols du Ghana:

     
  1. i)

    cartographie des latérites et sols latéritiques,

     
  2. ii)

    cartograhie des sols saprolithiques

     
.

Une évaluation quantitative est ensuite entreprise, en utilisant les cartes et des coupes, et l'article discute les problèmes rencontrés, de même que ceux liés aux essais de laboratoire, parfois spécifiques des régions tropicales. On insiste sur la géologie de base et les facteurs génétiques qui permettent de prévior et de cartographier les différents sols sous l'angle géotechnique. Le coût et les délais de réalisation des études sont également évoqués.

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References

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Copyright information

© International Association of Engineering Geology 1996

Authors and Affiliations

  • Ayetey J. K. 
    • 1
  • Frempong E. M. 
    • 1
  1. 1.Geotechnical Engineering DivisionBuilding and Road Research Institute (Council for Scientific and Industrial Research)UST-KumasiGhana

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