Detailed Investigation of Index Properties and Rate of Consolidations of Nguzu Edda Lateritic Soils (South-Eastern Nigeria) Used for Road Construction

Abstract

This research project involves detailed investigation of index properties and rate of consolidations of Nguzu Edda lateritic soil used for road construction so as to give details of soil behaviour in solving engineering and environmental issues. Nguzu Edda lies within the Afikpo Syncline of the Southern Benue Trough, Nigeria. It is located within longitude 7°491 E to 7°541 E and latitude 5°451 N to 5°501 N covering an area extent of about 62km2. Seven (7) samples were collected for the geotechnical analysis. Some geotechnical parameters were used to assess the lateritic soils. All the analyses were carried out in accordance with the British Standard code of practice (BS1377:1990). The results indicated that the particle size gradation for gravel ranged from 58 to 89%, sand ranged from 2 to 10% and fines ranged from 9 to 35%; natural moisture content ranged from 4.95 to 12.03%; specific gravity ranged from 2.49 to 2.64; the bulk density ranged from 1662.1 to 1775.2 kg/m3, dry density from 1498.7 to 1689.2 kg/m3; the liquid limit ranged from 32 to 38%, plastic limit ranged from 21 to 25%, plasticity index ranged from 8 to 13%; linear shrinkage ranged from 10 to 16%; the maximum dry density ranged from 1.78 to 1.95 mg/m3, optimum moisture content ranged from 9.1 to 20%; the undrained triaxial test for cohesion (C) ranged from 130 to 146 kN/m2 and angle of internal friction (O) ranged from 15° to 20°; the values of free swell index ranged from 12 to 30.8%; the California bearing ratio values for unsoaked condition ranged from 51.29 to 87.50% while soaked California bearing ratio ranged from 33.48 to 62.50%. According to America Association of State Highway and Transport Officials (AASHTO) soil classification, all the samples can be classified as A-2 materials which consist of silty or clayey-gravel and sand and can be rated as excellent material for road construction. They satisfy Federal Ministry of Works and Housing requirements for subgrade and subbase materials. Samples S2, S6 and S7 may likely be suitable only for sub base course materials. The soil samples tested from the study area are adjudged suitable for sub grade, sub base and base course materials.