Effect of Engineering Properties of Soil on Pavement Failures in Ogbagi - Akoko Area, Southwestern, Nigeria

Geotechnical properties of lateritic soil from 8 failed and 2 un –failed sections of road along Ogbagi and Arigidi Akoko, Southwestern Nigeria were investigated to determine the causes of the road failure. Tests carried out were natural moisture content, specific gravity, grain size distribution, atterberg limits, linear shrinkage, compaction and California bearing ratio. From the test results, natural moisture content ranged between 6.75 and 25.5 %, specific gravity (2.68 and 2.76), linear shrinkage (5.7 and 11.4 %) , maximum dry density (1483 and 1780 kg/m3), optimum moisture content (13.5 and 26.0 %), CBR (14 and 31%), liquid limits (31.1 and 53.5 %), plastic limits (0 and 28.2 %) and plasticity index (0 and 29.5 %). Factors responsible for the failure of the pavement are stress induced associated with high swelling of the soil due to ingress of water through joints or cracks, poor engineering properties of the soil due to high percentage of fine materials or clayey nature of topsoil/sub-grade soil below the pavement, poor compaction and drainage systems of the road. Keywords: Atterberg limits, Engineering properties, lateritic soil, pavement failures, grain siz

Electrical Resistivity Sounding for Subsurface Delineation and Evaluation of Groundwater Potential of Araromi Akungba-Akoko Ondo State Southwestern Nigeria

Electrical resistivity sounding of Araromi area of Akungba Akoko was conducted with a view to delineating the subsurface units and evaluating the groundwater potential of the area. Forty (40) Schlumberger vertical electrical resistivity soundings were acquired with ABEM SAS 1000 Resistivity Meter. The electrode spacing (AB/2) was varied from 1 – 65 m with maximum spread length of 130 m. The interpretation of the data was quantitative, and involved partial curve matching and computer iteration technique using WinResist software. Three to four distinct subsurface geologic layers were identified from the geoelectric layers, aided by borehole lithological logs. These included a lateritic clay/sandy clay/clayey sand/sandy topsoil, clayey weathered layer, partially weathered/fractured basement and the fresh basement with resistivity and thickness values of 3-174 ohm-m and 0.7-1.5 m; 196-472 ohm-m and 3.9-20.1 m; 533-742 ohm-m and 1.8-4.2 m; and infinity ohm-m respectively.. The depth to bedrock varied from 0 to 20.1 m. The bedrock relief was generally uneven, with bedrock elevations that varied between 312 and 346 m above sea level. The bedrock relief map delineated two major parallel basement depressions striking approximately NW-SE as the major groundwater collecting centers. The isopach map of the overburden showed generally thin overburden (< 15 m). The weathered/fractured layer constituted the dominant aquifer units with tendency for low groundwater potential rating arising from the clayey and thin nature of the overburden. Future groundwater resource development in the study area is considered feasible in few places characterized by relatively thick and sandy column of the overburden units. Keywords: Schlumberger, Sounding, Electrode, Resistivity, Thickness, Groundwater, Ratin

Geoelectric Assessment of Groundwater Prospects in Supare Estate, Supare Akoko, Southwestern, Nigeria

Abstract: The geoelectric assessment of the groundwater prospects in Supare Estate, Supare Akoko, Southwestern Nigeria, has been carried out in this study. The study area is underlain by Precambrian Basement Co mp lex rocks of Southwestern Nigeria. These rocks are inherently characterized by lo w porosity and permeability. The interpretation of fourtee