Scholarly Publication
Permanent URI for this collection
Browse
Recent Submissions
Now showing 1 - 5 of 139
- ItemGeophysical, Geotechnical and Groundwater Quality Assessment of a Proposed Sanitary Landfill at Gosa Village, Abuja, Nigeria(Journal of Mining and Geology, 2017-08-27) Ige, O.O.; Ojulari, Bashiru AlabaGeophysical, geotechnical and water quality investigations of Gosa dumpsite in Abuja were carried out with a view to investigating the feasibility of upgrading it to a modern sanitary landfill. Nineteen Vertical Electrical Soundings (VES) were carried out for geoelectric characterization of the site. Also, eight soil samples (two undisturbed samples and six disturbed samples) were obtained for geotechnical analysis. Inversion of the VES data indicated 3 to 4 geoelectric layers namely; topsoil, laterite, weathered basement and fresh basement. Depth to basement varied from 4.1 m to 27.2 m. Geotechnically, the soil samples from the study area were classified as well graded clayey-sand to silty-sand. Plasticity of the clay fraction of the samples varied from low to intermediate. Maximum activity of clay (Ac) of 0.6 showed presence of inactive clay. Permeability test showed that the permeability of the sample ranges -7-6 between 5.1 x 10 m/s-1.1 x 10 m/s which makes the groundwater prone to leachate pollution.
- ItemESTIMATION OF RESERVES AND ROCK SUITABILITY FOR CONSTRUCTION USING BASIC GEOLOGIC MAPPING AND GEOTECHNICAL METHODS: A CASE STUDY OF AN ABANDONED QUARRY SITE AT BUARI, SOUTHWESTERN NIGERIA(NSUK Journal of Science & Technology (NJST), 2020-08-27) Alu, O. O.; Bappah, A. A.; Amir, A. W.; Ojulari, B. A.; Agboola, R. O.Assessment of economic viability and rock suitability for construction at an abandoned quarry site at Buari village which lies between co-ordinates 8027’24.1”N to 8027’22.6”N and longitude 004055’36”E to 004055’ 26.4”E in Southwestern Nigeria was carried out by estimating the reserve tonnage at the area of study. This involves gridding, specific gravity determination, reserve estimation and life span determination. The entire area was gridded into 50 regular grids and was labeled 1-50. The elevations of different points on the area were measured in order to produce the contoured elevation map. Rock thickness of each grid was calculated. To ascertain the suitability of the rock from the area of study geotechnical tests was carried out on a sample. This involves thin section analysis, bulk density determination, Aggregate Impact Value (AIV) test and Aggregate Crushing Value (ACV) test. The elevation contoured map shows that the lowest elevation in the study area is 275 m while the highest elevation is 290 m. The 3D model of the rock generated from elevation using Surfer 12 shows that elevation is lowest in the southern part of the study area .The elevation increases northwards from the previous quarry face to the top of the hill. The Specific Gravity (SG) = 2.71, Σ (reserve volume of the each grids (RVG) (m3) = 2457.84 m3and the reserve tonnage of rock in the area of study is 6660.75 tons. This can only support an adopted exploitation rate of 18.25 ton per day for one year. Hence, the rock is considered unsuitable for mining and their economic viability is considered is very low. The specific gravity (SG) of the rock sample tested is higher than the minimum value of 2.60 recommended for rocks that are suitable for construction purposes. Average value of the results of Aggregate Impact Value (AIV) of the rock sample is 22.79%. Hence, this value certified the rock sample for use as concrete and for wearing surfaces, such as runways roads and pavement. Result of the Aggregate Crushing Value (ACV) test conducted on the selected samples is 11.17%. Hence, the rock sample from the study area is suitable for use as concrete for roads and pavements and for other structures.
- ItemGeo-Electric Assessment of Kali Failed Dam Project Aliero, North Western Nigeria(International Journal of Geosciences, 2020-08-27) U. Z. Magawata; Ibrahim Mohammed; B. A. Ojulari; A. I. Augie; Salisu MusaAn integrated geophysical investigation using very low frequency electro magnetic (VLF-EM) and electrical resistivity methods using (VES) technique has been carried out for investigation of possible causes of dam failure in Kali, Aliero Northwestern Nigeria. A total of Three 3 (VLF-EM) traverses and Ten 10 vertical electrical soundings (VES) techniques have been carried out to identify the fracture zones, seepage and possible threat that lead to the col lapse of the dam. The interpretation of VLF-EM data is carried out qualita tively using Fraser and Karous-Hjelt filters and the interpretation of sounding data is done using IPI2 win software. VLF-EM data signifies the exact fracture zones founded on higher values of relative current density that coincide to the subsurface fracture. The survey was conducted on an interval of 10 m interval along traverses at South-North direction ranging from 620 - 640 m in length. The plot of filtered real and filtered imaginary identified noticeable fracture zone close to the surface which was later further delineated by (VES) tech nique. VES soundings were carried out at locations of prominent VLF ano malies presumably typical of basement fracture using AB/2 of 80 m. Results interpreted show layers thickness and their corresponding resistivity, top soil (0.5 m to 3.45 m, 51.9 Ωm to 318 Ωm), underlain by clay to confined clay (4.56 m to 54 m, 7.88 Ωm to 60.2 Ωm) which is underlain by fractured/fresh basement (5.76 m to 73.9 m, 40.3 Ωm to 197 Ωm). The overburden materials underlain are far away to subsurface (bed rock) in most of the area to support the dam. The clay materials which could serve as conduit, exist within the shallow overburden which was not excavated during the construction. Therefore it was concluded that the dam cannot retain its strength to oppose the dam against collapse.
- ItemAssessment of saltwater–freshwater interactions using water samples and borehole logging information in the Lagos coastal region, Nigeria(Environmental Earth Sciences, 2021-07-27) M. A. Yusuf; B. A. Ojulari; K. O. Ibrahim; T. A. AbiyeAn analysis of borehole logs with hydrophysical data from the Lagos coastal belt, Southwestern Nigeria, was carried out to evaluate the subsurface lithological units and geo-environmental impact of seawater intrusion into coastal freshwater. Forty f ive (45) borehole logs, consisting of natural gamma, electrical resistivity log and hydrophysical parameters were integrated to delineate saline and fresh aquifer zones and propose simplified conceptual models for adequate groundwater characterisation and development. The qualitative interpretation of the borehole logs revealed a complex lithology of alternating sequences of sand and clay layers. The study also showed that the subsurface was variably intruded by saline water indicated by low resistivity values with freshwater/saline water boundaries occurrence at depths ranging between 14 and 157 m from west to east. The variation in depths of occurrence of freshwater/saline water interface is dependent principally on the proximity to saline/brackish water source as well as variation in lithology. Complementarily, the average electrical conductivity (EC) of 1770 μS/cm (GW1–7) and 1676 μS/cm (GW8–13) recorded in groundwater at Apapa in the west and Island at the central part, respectively, further confirmed saline incursion of the coastal aquifers in the region. This study demonstrates versatility of geophysical borehole logs in identification and differentiation of the subsurface lithology and its fluid content.
- ItemElectrical Assessment of Aquifers in the Basement Complex of Unilorin: Implication for Existing Boreholes(Journal of Science, Technology, Mathematics and Education (JOSTMED), 2015-08-27) Ojulari, Bashiru Alaba; Saminu OLATUNJISchlumberger 4-electrode array was employed to sound 21 stations. IPI2WIN and surfer12 softwares were used to infer lithological series, aquifer thickness and depth. The aquifer hydraulic conductivity K and transmissivity T were calculated from the VES data using the Dar Zarouk principles. The area shows 3 and 4 geo-electric layers from the computer iteration. The layers were interpreted as the topsoil (130- 1469 Ωm), clayey (wet to dry) (52.6- 8552 Ωm), weathered/fractured basement (46.2-249 Ωm) and fresh basement (454-5022 Ωm). The aquiferious zones lie within the second and third layers. The aquifer depth is between 6.17 m and 24.9 m while the thickness range is 1.89-22.7 m. The longitudinal conductance S ranges from 0.02 to 0.468 Ω-1and transmissivity T varies from 246 to 2419.8 Ωm2. The results conformed with the functional boreholes, such as at VES 3, sited in areas with thickest aquifers and highest transmissivity T. The NE and NW parts were found most suitable for fresh water exploitations. Low longitudinal conductance which implies low protective cover, in the vicinity of the borehole near VES6 confirmed the contamination claim of its water.