Geotechnical Characterization of Soils in Ahoada Town, Rivers State for Safe Foundation Design and Construction (Published)
A geotechnical investigation was conducted to evaluate the subsurface conditions and assess the suitability of soils for shallow foundation construction in Ahoada town, Rivers State, Nigeria. The study involved field sampling and laboratory testing of soil samples to determine relevant geotechnical parameters such as grain size distribution, Atterberg limits, moisture content, and shear strength characteristics. The geological setting of the area is typical of the Niger Delta sedimentary basin, characterized by alternating layers of sand, silt, and clay deposits. Results show that the near-surface soils consist predominantly of clayey sand and sandy clay layers underlain by more competent sandy strata at greater depths. Results obtained show that the Atterberg limit results reveal that the liquid limit ranges from 53.5% to 97.8%, the plastic limit ranges from 30.1% to 60.0% while the plasticity index values range from 17.1% to 39.5%. The cohesive soils (clays) are highly plastic (CH) in the Unified Soil Classification System (USCS) designation. The natural moisture content ranges from 71.3% to 97.5%. The particle size distribution analysis reveals that the sand is fine to medium to coarse grained and in a medium dense state of compaction and based on its coefficient of uniformity and gradation classifies as poorly graded (SP) by the USCS designation. The moisture content of the sand ranges from 8.9% to 13.0% while the bulk unit weight ranges from 19.6KN/m3 to 20.3 KN/m3. The angle of shearing resistance ranges from 260 to 330. The result of the undrained shear strength of the clay ranges from 16Kpa and 19Kpa. The clay is very soft to soft and exhibit medium to high moisture content. The strength test result indicates a material of low undrained shear strength, the coefficient of consolidation, Cv of the clay soil samples varies between 1.40m2/year and 2.69 m2/year. The coefficient of volume compressibility, Mv, for the same materials varies between 0.215 m2/MN and 0.657 m2/MN, generally indicating clay layers of high to very high compressibility. The high groundwater table and presence of compressible clay layers in the upper strata pose challenges for shallow foundation design. However, with proper foundation design, including soil improvement or adequate footing depth, shallow foundations can be safely adopted in areas with adequate bearing capacity.
Keywords: Groundwater, foundation design, geotechnical characterization, soil stability
Geological and Hydrogeophysical Investigation of Angwan Zakara, Keffi Sheet 208N.E of North Central Nigeria (Published)
The geological and hydrogeophysical assessment of the groundwater prospect/potential in Angwan Zakara and its environs, Karu Local Government, Nasarawa State, North-Central, Nigeria has been carried out in this study. The study area covers 25km2.The area is underlain by the Basement Complex of the North-Central Nigeria consisting of Medium grained biotite granite, biotite gneiss, phyllite and un-mappable muscovite schist with structural features such as joints, veins, foliation, faults, and xenoliths trending NW-SE direction. Forty Nine (49) Vertical Electrical Sounding were carried out in the study area using Omega Resistivity Terrameter, GPS12 Garmix with a maximum cable spread of AB/2=100m and MN/2=5m. The results obtained from the field data were interpreted using IXID Software for quantitative analysis. True resistivity map, piezometric map, basement resistivity map and depth to basement map were prepared and interpreted using computer software for qualitative analysis (SURFER 8). From the IXID interpreted results, five (5) curve types were obtained from the acquired data namely A, H, KH, AH, and HK curve types are the dominant. The study area showed depth to basement ranges from 20-90m. That revealed good groundwater potential. The study area revealed 4-7 lithologic sequences consisting of top soil, laterite, clay, weathered/ fractured basement however the host rocks in the study area are biotite granite, quartzite and schistose-gneiss. The results obtained shows that the direction of water flows revealed five ridges R1-R5 and four depressions D1-D4 with receptacles trends of the ridges are R1 and R2:NW-SE; R3 N-S, R4 : NE-SW and R5; E-W. The geoelectric sections were produced and correlated with the geology of the study area and it was found to be in conformity with the each other. Based on this, the study area is zoned into three namely good, moderate and poor groundwater potential zones.
Keywords: Assessment, Geologic, Groundwater, hydrogeophysical, potential, quantitative and qualitative
Delineating Saline Water Zones in an Inland Brine Area Using Electrical Resistivity Indicators (Published)
This paper presents results of saline groundwater zone delineation using electrical resistivity sounding. The geologic setting of the study area, Awe Town is that of the Biddle Benue Trough, a structure filled with Cretaceous sediments that include Awe Formation. The town is a predominantly rural area plagued with saline groundwater resulting from brines associated with Awe Formation. As a result of this challenge, water supply scheme for the area was situated about 6km away from the main settlement making access to potable water difficult. The present study was prompted by the need to delineate the extent of groundwater contamination by the brines and in so doing identify aquifers close to the settlement for exploitation. Electrical resistivity method has been applied extensively in delineation of saline groundwater zones. Electrical resistivity surveys were done around the town with the sole aim of delineating the saline groundwater and fresh groundwater regions around the settlement. A total of 20 vertical electrical soundings were carried out using the Schlumberger configuration. Geophysical indicators (longitudinal conductance and transverse resistance (S and T respectively) as well as transverse resistivity (ρt) and longitudinal resistivity (ρl)) were used to assess saline water distribution in the aquifers of the study area. Of the four indicators, Longitudinal Unit Conductance and Transverse Unit Resistance clearly demarcated saline groundwater zones. Contour maps showing the distribution of these indicators aided in the identification of fresh groundwater, 1.2km from the main town. Analysis of borehole logs in the fresh groundwater region revealed fresh groundwater aquifers within Younger rocks i.e. Ezeaku and Keana Formations, which overlie the Awe Formation. Geologic setting of the study area is such that Awe Formation is exposed in the Old Town due to uplift and weathering, while younger rocks of Ezeaku and Keana Formations overlie Awe Formation in the New Town area. Aquifers in these formations have resistivity in the range of 150 to 300Ωm, with thicknesses ranging between 20m and 35m; these zones were interpreted to have high yield potential in terms of quality.
Keywords: Groundwater, Saline, electrical resistivity, inland brine
AZIMUTHAL SQUARE ARRAY RESISTIVITY SOUNDING OF SHALLOW SUBSURFACE FRACTURE DISTRIBUTION IN PARTS OF THE EASTERN BASEMENT COMPLEX OF NIGERIA (Published)
Azimuthal square array resistivity sounding method was carried out at twelve (12) locations within Parts of the Eastern Basement Complex of Nigeria. The field data were collected using ABEM Terrameter with other accessories. For square – array, the location of measurement point is the centre point of the square and array size of 28m and 42m, 56m and 70m were used and each square was rotated in 150 increments about the centre point for a total of 3600.Data were analyzed using Origin pro. 8.0 Software. The results of the study showed the presence of fracture zones and seven (7) of the fracture zones were oriented in the NE – SW direction, while six (6) were oriented in the NW – SE direction indicating that the study area is has good potentials for ground water development.
Keywords: Abem Terrameter, Basement, Fracture, Groundwater, Resistivity, Square Array