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  • Effect of rock-water interactions in Calabar area

  • The study area, Katsina town and its environs, is located in Katsina State, northwestern Nigeria. It is defined by longitudes 7° 30'E to 7° 45'E and latitudes 12° 52' 10"N to 13° 07' 10"N with a total area of 625km2.\r\n\r\nThe objective of the project was to study the hydrogeochemical characteristics of water in the area and the impact of waste dumps on the water quality. The methods adopted for the project were geological mapping, geophysical studies, hydrogeological mapping and waste management assessment coupled with laboratory analyses of water and soil samples.\r\n\r\nThe area is underlain by both Crystalline Basement rocks and sedimentary rocks and it lies at the eastern periphery of the Iullemmeden (Sokoto) Basin. The conglomeratic sandstone of Gundumi formation constitute the aquifer in the sedimentary area while the weathered overburden, fractured and jointed zones constitute the aquifers in the basement underlain areas as revealed by geophysical studies.\r\n\r\nThe water type in the project area is earth-alkaline (calcium and magnesium) and predominantly chloride (Cl-) and bicarbonate (HCO3-) water species.\r\n\r\nThere is no officially-designated waste dumpsite(s) in the project area, which resulted in indiscriminate dumping of wastes in unapproved sites such as road sides, drains, streams and river channels. Handdug wells, hand pump boreholes and deep boreholes are located indiscriminately close to dumpsites, latrines, septic tanks and drains.\r\n\r\nThe physical and chemical parameters of the water samples particularly those of the groundwater conformed with international standards of potable water except groundwater in the vicinity of dumpsites, that had electrical conductivity, total dissolved solids, nitrate, chloride and Coliform Counts exceeding the WHO and SON maximum permissible limits in drinking water, which rendered the water unfit for human consumption, unless treated.\r\n\r\n\r\n

  • Determination of in-situ soil conditions

  • The project area, Enugu and environs, is defined by Latitudes 60 14' 15" to 60 31' 20" North of the Equator and Longitudes 70 22' to 70 35' 20" East of the Greenwich Meridian. It covers towns and villages such as Ngwo - Enugu, Ukana, Oriemba and Ninth Mile Corner with Enugu urban at the Centre.\r\nThe cuesta is the dominant physiographic feature that trends North-South west of Enugu town. It acts as water divide for groundwater and surface water between the Anambra Basin to the west and the Cross River Basin to the east. The project area falls within the Anambra Basin and is geologically underlain by Agbani Sandstone, Enugu Shales, Mamu, Ajali and Nsukka .Physico-chemical interpretation of groundwater in Enugu

  • The study area is approx 625km2, which includes Kaduna town at the centre with large settlements like Tudun Nupawa, Kurmin Mashi, Mondo and Rigasa to the west, Kabala and Burnawa to the south; Maliali and Unguwan Rimi to the east and Unguwar Kanawa, Badarawa and Rigachukun to the east. The major river channel is the river Kaduna which cuts the area from the west. Other rivers are river Gora to the south and river Kura to the North.

  • Fifty-four (54) bulk samples were taken from test pits dug to a minimum depth of 1.5 metres for Atterberg Limits Test, Grain Size Distribution analysis, Compaction, and California Bearing Ratio determination.\r\n\r\nTwelve (12) shell and auger boreholes were drilled using the Pilcon Wayfarer 1500 percussion rig. The boreholes were advanced to 10 metres depth. Undisturbed samples were collected in Shelby tubes at selected intervals of 1.5metre from each other for Triaxial Compression Test, Consolidation test and Grain Size Distribution analysis.\r\n\r\nTwelve (12) Dutch Cone Penetrometer Sounding Tests were carried out at 10 metres depth or to refusal. The resistance of the soil was measured by means of a dial guage attachment to the penetrometer machine. Readings obtained and the graphical plots of the soil resistance were used to determine the allowable bearing pressure of the soil.\r\n\r\nResults of the grain size distribution analysis show a consistent increase in grain size with increasing depth. The soils classify as very fine sands, silty to clayey fine sands, or clayey silts with slight plasticity (ML), and gravelly clays, sandy and silty clays (CL) according to the Unified Soils classification scheme (USC).They have good to poor, and good to fair compaction characteristics respectively. They show high compressibility, moderate permeability and are excavatable and stable as fill material, but would be unsuitable as base course.\r\nTheir bulk density showed a range from 1.95Mg/m3 to 2.19 Mg/m3, their natural moisture, a variation from 12% to 21%, while their optimum moisture content ranges between 9.5% and 19.8%. Cohesion values range from 28 kN/m2 to 60 kN/m2, and maximum dry density ranging between 1.09 Mg/m3 and 2.17 Mg/m3 were recorded. The soaked and unsoaked California Bearing Ratio (CBR) values of 5.1% to 11.2% and 7.6%to18.9% were registered respectively. No ground water was encountered during the operation.\r\nFor design of strip/square footing 1.5metres wide founded at 1.5metres depth, the average allowable bearing capacity of soil would be 25 kN/m2 from cone, while the sleeve gives 50 kN/m2, allowing maximum differential settlement of 25mm (1 inch), using a factor of safety of 3.\r\nFor the same footing, under same conditions, the average allowable bearing capacity would be 125 kN/m2 for Standard Penetration Test, while the average allowable bearing capacity of 279 kN/m2 was computed for same footing under same conditions from the Undrained Triaxial compression Test. \r\n\r\nTherefore, it is recommended that the Dutch Cone Penetration Test average bearing capacity of 25 kN/m2 be used for design. However, it must be ensured that no ingress of water be allowed into the foundation. Alternatively, a raft foundation may be necessary for design. If a pile foundation is adopted, it must be imperative to carry out a pile loading test.\r\n

  • Determination of in-situ soil conditions

  • Determination of in-situ soil conditions

  • Determination of in-situ soil conditions

  • Thirty-seven (37) bulk samples taken from a depth of 1.5 meters were analyzed for the determination of Atterberg Limits, Linear Shrinkage, Grain Size Distribution, compaction, and California Bearing Ratio (CBR).\r\n\r\nSixteen (16) borings were made to a depth of 10 meters or to refusal. Standard Penetration Test (SPT) was carried out at every 1.5 meter depth interval and undisturbed samples were collected at the same depth or change of material for Triaxial Compression Test, Grain Size Distribution analysis, and Consolidation. All boreholes stopped at between 1.1m and 5.3 m except borehole 16, cell 056 at NYSC Zonal Office, which went to a maximum depth of 10 meters. \r\n\r\nTen (10) Dynamic Cone Penetrometer (DCP) tests were carried out using a 25mm thin walled pipe with 600 cone. Due to the fine grained nature of the dominantly clayey material, particle size distribution analysis by hydrometer method was employed.\r\n\r\nResults of field and laboratory tests reveal that the entire area on the average is overlain by a 2.5m thick sand, silt, and clay, with spot clay deposits notably at cells 056 (NYSC Zonal office) and 047 (Railway quarters). Soils of Gombe can be classified into nine groups, A-3, A-4, A-5, A-6, A-7, A-1-b, A-2-4, A-2-6, and A-2-7. Of the 37 samples analyzed, 18 are sands and hence non-plastic, 2 are silts and plotted below the A-line on the plasticity chart, while17 others are clays and plotted above the A-line.\r\nResults of SPT tests at cell 001 to 060 gave blow count (N) values of between 2 and 100 with calculated corrected N-values (N?) of between 2 and 58, at 0.5m, 1.5m, 3.0m, with maximum depth of 10m at NYSC Zonal Office. Apart from the boring at NYSC Zonal office, all borings terminated at between 1.1m to 5.3m.\r\nFrom the bulk samples recovered at 1.5m depth, bearing capacity computations based on Triaxial Compression test gave values between 277kN/m2 and 2545 kN/m2. \r\nConsolidation test results show that the materials are of medium to high compressibility. About 90% consolidation occurred within 40-120 metres, indicating secondary settlement upon application of load. The 24-hour soaked California Bearing Ratio (CBR) values between 5.1% and 11.2% shows the materials are good to be used for road subgrade. Values of maximum Dry Density (MDD) ranging between 1.09Mg/m3 and 2.17Mg/m3 with optimum moisture content (OMC) ranging from 9.5% to 19.8% were recorded. Linear shrinkage test shows low shrinkage for the sandy material, and shrinkage of up to 14% for the dominantly clayey materials. \r\n\r\nCivil constructions in Gombe require strict adherence to building standards and the findings of this work in the light of the thick clay that underlies most part of the state capital. This can go a long way in reducing incidence of multiple cracked buildings that are scattered all over the area. \r\n