Geoelectrical and Geotechnical Characterization of Different Types of Soil in Ede, Osun State, Nigeria

Geoelectrical and geotechnical investigations were carried out to characterize soils from different locations in Ede, Osun State, Nigeria for engineering purposes. Wenner electrode configuration technique was deployed in carrying out the geoelectrical survey of about 40m for each profile. The data analysis was approached by plotting the apparent conductivity against electrode spacing (s) and the result was interpreted. The geoelectrical resistivity survey revealed locations 1 and 2 with resistivity values of 25.01-419.22ohm-m (conductivity 0.002 - 0.194 (ohm-m)-1and 5.5-1246.57 ohm-m (conductivity = 0.0002 - 0.001 (ohm-m)-1) respectively could be classified as clay. Sample 3 recorded a resistivity value of 1.00- 22,787.39 ohm-m (conductivity= 0.00004- 1.00 (ohm-m)-1) thus, was classified as silt/sand respectively. Soil from the said different locations in Ede, Nigeria, were tested in the Laboratory for certain properties like Atterberg limits, specific gravities, sieve analysis, compaction test, etc. and the results showed that samples 1, 2 and 3 have specific gravity values of 2.50, 2.13 and 2.40 respectively and could therefore be referred to as organic soil. Samples 1, 2 and 3 have maximum dry density (MDD) of 1.45g/cm3, 1.92g/cm3, 1.95g/cm3 and optimum moisture content (OMC) of 15.40%, 13.36% and 9.61% respectively. The analysis conducted in this study revealed that the soil type found in Ede, Nigeria could be classified as silt-clay, sandy clay, clay and sand

Ground Magnetic Attributes For Subsurface Structural Analysis of Foundation Beds in a Sedimentary Terrain in Southwestern Nigeria: OSUSTECH Permanent Site as a case study

The structural failure such as subsidence, collapse and cracking of the walls of buildings in Nigeria has posed a threat or a significant potential hazard to the community in the affected areas. These hazards include gross loss of valuable lives and properties that always accompany such structural failure. Therefore there is need for subsurface structural analysis. The Stop-And-Go method was used for the acquisition of the data. This method is good for subsurface investigation at depths below 30 metres (100 feet). Data for this study were taken at a 10 metres station spacing which is about half that of the expected depth of target. The method requires the technique of measuring total field components at discrete points along the traverses distributed regularly throughout the survey area of interest. The raw data were processed to remove diurnal variations from the total field data measured from the base station. Interpretation of the ground magnetic data revealed that the study area comprises zones underlain with thin to thick overburden. In all the profiles, the regions A and B are associated with the high magnetic values except in the profile 4 in which only region E is associated with high magnetic values. Thus, the region E in the profile 4; the regions A and B in the profiles 1, 2, 3 and 5 are competent zones for the sitting of structures. It can be deduced that the regions of high magnetic susceptibility and high resistivity are competent zones for construction of high rise buildings and other engineering structures. While the regions of low magnetic susceptibility and low resistivity could pose problem of subsidence of the buildings around the region

Investigation of Sub Soil Corrosion Using Electrical Resistivity Method: Federal University Oye Ekiti Phase II Campus as a case study

Electrical Resistivity survey was carried out with the aim of identifying the degree of soil corrosion associated with the sub soil of the Federal University Oye Ekiti phase II. The sub soil resistivity of the area was surveyed and evaluated using Ohmega resistivity meter. The sub soil resistivity parameters were used to delineate the degree of the sub soil corrosion. Four electrodes were inserted into the soil/rock using the Wenner profiling, vertical electrical sounding and Dipole- Dipole array along the traverses with a spacing of 5m and n =1 to 5.In this method, artificially generated electric current(I) was injected into the ground via two current electrodes while the resulting potential difference (V) is measured by another pair of electrodes. The survey revealed that the Southwest and Northwest regions of the study area were associated with high resistivity (200-500 Ω-m).This implies that the soil structure of the region is not corrosive, while the southeast region was associated with low resistivity (20-80 Ω-m) value which implies that the sub soil structure is corrosive. The degree of corrosion increases from the western to eastern part of the study area which may be due to bedrock topography. Of all the layers investigated, the topsoil layer is highly corrosive compare to other layers

Interpretation of aeromagnetic data over Abeokuta and its environs, Southwest Nigeria, using spectral analysis (Fourier transform technique)

This study presents the results of spectral analysis of magnetic data over Abeokuta area, Southwestern Nigeria, using fast Fourier transform (FFT) in Microsoft Excel. The study deals with the quantitative interpretation of airborne magnetic data (Sheet No. 260), which was conducted by the Nigerian Geological Survey Agency in 2009. In order to minimise aliasing error, the aeromagnetic data was gridded at spacing of 1 km. Spectral analysis technique was used to estimate the magnetic basement depth distributed at two levels. The result of the interpretation shows that the magnetic sources are mainly distributed at two levels. The shallow sources (minimum depth) range in depth from 0.103 to 0.278 km below ground level and are inferred to be due to intrusions within the region. The deeper sources (maximum depth) range in depth from 2.739 to 3.325 km below ground and are attributed to the underlying basement