International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 8, Issue 1, pp: (196-203), Month: April 2020 - September 2020, Available at: www.researchpublish.com
Geotechnical Properties of Offa Lateritic Soils and its Suitability as Subbase and Base Materials J.A. Ige1, B.A. Ibitoye2, M.B. Kazeem3 1
Department of Civil Engineering, Ladoke Akintola University of Technology, Ogbomoso, Nigeria 2
Department of Civil Engineering, Kwara State University, Malete, Nigeria..
3
Department of Civil Engineering, The Federal Polytechnic Offa, Offa, Nigeria. Correspondence: jaige@lautech.edu.ng
Abstract: The determination of the suitability of the base, subbase and subgrade materials are important in road construction. This study evaluate the geotechnical properties of Offa lateritic soils and its suitability for use as subbase and base materials. The index properties, compaction, CBR and coefficient of permeability were conducted on the lateritic soils from the pits. The results revealed that the SG of the soil from the pits are within the specified range for lateritic soil. The NMC of pits A to D, conform to specified limit for road constructions while sample E does not conform to the specified range. The soils from pits A and B; and C and E, fall under group A-6 and A-7-6, respectively, while soil from pit D fall under group A-2-7. Soils from four pits are within the specified limit for LL while soil from one pit is above the limit. The CBR value of WAS shows that lateritic soils from three pits are suitable for use as subbase materials while lateritic soils from two pits are suitable for use as base materials. Lateritic soils from four pits under the AASHTO unsoaked are suitable for use as base materials, whereas only soils from one pit are suitable for use as subbase materials. However, all lateritic soils from under BS are suitable for use as subbase materials. The results of this study will be useful for road construction in Offa and its environs, thereby serving as guide for future road pavement design. Keywords: Offa-Lateritic soil, Index properties, Strength properties, Subbase and Base.
1. INTRODUCTION The determination of the suitability of the base, sub-base and sub-grade materials are important for a highway Engineer to enable him identify and classify the materials, measure its strength, evaluate its drainage properties and help in processing the soil as a highway material. Base, sub-base and sub-grade materials are majorly composed of lateritic soil, which in the engineering field refers to all unconsolidated material in the earth crust i.e. all material above bedrock. Soil samples contain; Mineral and organic particles Water Air. The relative amounts of these three phases are indication of the soils properties and conditions (Oke et al., 2009; Nwankwoala and Amadi, 2013). Lateritic soils are common surface deposits occurring in the tropical and subtropical regions of the world, enriched in iron and aluminium and developed by intensive and long lasting weathering of the underlying parent rock. In Nigeria, laterites serve as the perfect soil materials to solve construction problems such as construction of earth dams, highways, embankments, airfields and foundation materials to support structures without considering its classification as problem and non-problem types and the actual field geotechnical performance of the soils (Amadi et al.,2015; Ademila, 2017). Inadequate information on soils and their properties has led to failures of some road construction works in Nigeria. Base on poor condition of road in Offa (case study of Offa-Irra Road, Taiwo Road, Atanoba-Aleluya Road, Olofa Way-Idiogun
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