Journal of Numerical Mathematics

Odewumi S.C.

Mousavi Z., Jabbarzadeh M.

Khashman M.A., Shirazi H., Al-Dujaili A.N.

Ahanda B., Yolcu T., Watson R.

Oishi M., Yamamura T., Yamagishi R., Suzuki K., Koshiya H., Sakuno K., Akimoto R., Okada J., Abe S.

Kovalevskiy O., Cancelliere M.

Adeoye J.A., Yusuf I., Obaje N.G., Usman A.A., Okoro U.C.

Bienibuor A.K., Preko K., Aning A.A., Menyeh A., Wemegah D.D., Appiah M.K., Gyilbag A.

Stutter M., Baggaley N., Lilly A., Mellander P., Wilkinson M.E., Ó hUallacháin D.

Okewale I.A., Grobler H., Mulaba-Bafubiandi A.F.

Ogbuagu K.M., Ehirim C.N., Dagogo T.

In this study, a Clastic reservoir in the Y oil field located in parts of the Niger Delta was characterized geomechanically using suits of well log to estimate and evaluate its geomechanical properties. The study aims to use the estimated properties to infer the rock strength and probable mechanical failure mechanism using the cross-plot method. The estimated average value of these properties is 5.4135GPa, 1.534GPa, 6.053GPa, 0.3478, 0.653GPa−1 and 27.457GPa for Young's modulus, Shear modulus, Bulk modulus, Poisson's ratio, compressibility, and unconfined compressive strength respectively. The result of the cross plots of these evaluated properties colour-coded with porosity for the reservoir 2 intervals distinguished three lithofacies: hydrocarbon sands, brine sands, and shale with varying sensitivities in the reservoir interval. The cross plots of Poisson's ratio versus elastic moduli and UCS show that the porous hydrocarbon sands exhibit high Poisson's ratio, low elastic moduli, and low UCS, while brine sands and shale exhibit moderate Poisson's ratio and medium to high elastic moduli and UCS respectively. These suggest that the hydrocarbon sands are brittle and are said to be more prone to lateral deformation being less stiff, rigid, and having less strength than the other lithologies. At the same time, shale is ductile the stiffest, and the most rigid rock in the reservoir. These observations are indications that the hydrocarbon sands are friable and unconsolidated compared to the consolidated brine sands and shale. Thus, the low strength hydrocarbon sands are prone to mechanical failures and are likely to deform easily under the influence of overburden in the reservoir interval during production.

Ojo O.T., Ike C.J., Aladeboyeje A.I., Olaseeni O.G., Adewumi O.F.

Abstract Borehole water plays a critical role in providing drinking water in Effurun, Delta State, Nigeria. However, concerns about potential contamination from both natural and anthropogenic sources necessitate regular groundwater quality assessments. This study evaluates the hydrochemical properties of borehole water to ensure public health safety and to understand the groundwater's suitability for consumption. The aim of this study is to assess the quality of borehole water in Effurun by analyzing major ions, trace metals, and other hydrochemical parameters, and to compare the findings with WHO and NSDWQ drinking water standards. Ten borehole water samples were collected from various locations across Effurun. Hydrochemical analyses were conducted to measure cations (calcium, magnesium, sodium, potassium), anions (chloride, bicarbonate, sulfate, nitrate), and trace metals (lead, copper, zinc, manganese). Statistical analysis and spatial mapping were employed to evaluate the distribution of ion concentrations and identify areas of concern. Calcium levels in the boreholes ranged from 29.95 mg/L to 64.50 mg/L, while magnesium levels were more consistent, ranging between 9.50 mg/L and 14.20 mg/L. Sodium and potassium showed moderate correlations with calcium. Chloride levels varied widely, indicating potential contamination from seawater intrusion or industrial discharge. Elevated sulfate and nitrate concentrations pointed to agricultural runoff. Trace metals, particularly lead, exceeded safety limits, with lead concentrations ranging from 0.092 mg/L to 0.127 mg/L, posing significant health risks. Spatial analysis revealed varying ion concentrations across Effurun, with higher calcium and magnesium levels near water bodies, suggesting local geology's influence. The central area exhibited moderate ion concentrations, while the southeastern region had the highest calcium levels, possibly due to geological formations rich in calcium or human activities. The study highlights diverse hydrochemical characteristics of Effurun's borehole water, with some areas showing contamination beyond acceptable limits. Regular monitoring is essential to ensure safe drinking water and address potential health risks. The findings stress the need for improved water resource management and contamination control. This study provides a comprehensive spatial analysis of groundwater quality in Effurun, identifying specific areas at risk of contamination and offering data-driven recommendations for public health and sustainable water management.

Rana M.S., Hossain A.T., Hasan M.F., Rahman M.A., Biswas P.K., Zaman M.N.

Sand mining using dredging technology from channel bars is a common technique worldwide. To minimize adverse effects of dredging, geo-engineering nature of the soil should be evaluated before mining. Therefore, the present study deals with the potential risks associated with dredging for mineral sand extraction by analyzing the engineering geological properties of the soil from the Brahmaputra River bar and the surrounding areas, Bangladesh. A detailed engineering geological analysis was conducted using field and laboratory testing methods, including Standard Penetration Tests (SPT), mineralogy, grain size distribution (GSD), California Bearing Ratio (CBR), and direct shear tests. The findings divulge that the soil in the study area is light gray, unconsolidated, moderately sorted, poorly graded, and classified as fine-to-medium silty sand. SPT-based liquefaction potential assessments suggest that the soils are highly susceptible to liquefaction, particularly during dredging or seismic events. The study also identifies the risk of localized slumping and soil instability, which exacerbated by micaceous and quartz-rich sands. The CBR results further classify the subgrade as weak to medium-strong, indicating risks of slumping, erosion, and instability. The non-cohesive granular soil in the area may liquefy or be susceptible to erosion, wave attack, bank slope failures, and seepage development during and after dredging as indicated from GSD and direct shear test results. Thus, proper safety precautions, including soil stabilization techniques, controlled dredging, and slope reinforcement, should be taken before dredging on such river bar to minimize risk. This research offers practical guidance for dredging companies to minimize risks and improve soil stability, contributing to safer and more sustainable river bar dredging operations worldwide.

Ilori A.O., George A.M., Umoh I.C., Eyakndue E.O., Ukpekpe U.U.

The performance of pavement and bridges on a stretch of 21.4 km of Calabar—Itu highway is the focus of this study. Within this 21.4 km section, the pavement structure has completely failed while the three bridges within this section are still in good structural health as there is no failure of both superstructure and foundation. Three groups of shale soils characterize this stretch; these are Ekenkpon Nkporo, and New Netim Marl. The materials were characterized by both geotechnical and geophysical methods at shallow and deep surface. The Ekenkpon and Nkporo classifies as organic silt and clay with high plasticity (OH) and Inorganic silt, (MH) respectively, while New Netim marl classify as lean clay (CL). Geotechnical shear strength properties determined by Direct shear tests for Ekenkpon indicate cohesion value’C, of 36.1 kN/m2, angle of shearing resistance of 36.8°, that of Nkporo shale with cohesion value as 36 kN/m2 and angle of internal friction as 3.6°. Based on the shear strength properties, Ekenkpon shale has a bearing capacity of 3902.95 kN/m2, Nkporo shale has a value of 667.02 kN/m2, and New Netim Marl with a value of 319.75 kN/m2. Within the load range of 50 kN/m2 to 500 kN/m2 the compressibility values for Nkporo are between 0.29 and 0.23 per MPa, while that of Ekenkpon shale for the same load range is between 0.78 and 1.50 per MPa, showing Ekenkpon shale is highly compressible than the Nkporo shale. Shallow seismic refraction survey involving both p and s-waves were also deployed to evaluate the quality of soils at some locations along this alignment. Results indicate the near the surface horizon which serves as the foundation for highway pavement is composed of soil materials that are highly permeable, dispersive, collapsible, easily eroded as indicated by low Slake Durability Index with values between 6.9 and 51.42%; properties which are all dependent on changes in water content. Whereas at depth, the same soil sequence but stable as permeability to water is very low, hence the stability of bridge foundations in them.

Haque M.F., Ahmed I.

The axial force variation along the length of the jointed precast pile is influenced by the hard soil layer properties during construction. For this purpose, this research proposes an innovative concept of spring model of jointed precast pile to evaluate the axial force variations along the length to consider some variable parameters (i.e. soil elastic moduli, soil Poisson’s ratios, hammer loads, compressive strengths and sizes of precast piles). The linear elastic analysis is performed by using finite element-based software ETABS v. 18.1.1 to consider 3-nodded line element of the jointed precast pile. Variable parameters are influenced to increase the normalized axial force of the jointed precast pile because of increasing stiffness, self-weight, etc. The difference in result of 6.84% may indicate a good agreement with the verification of the numerical analysis. The rates of the normalized axial force increments for variable soil elastic moduli, soil Poisson’s ratios, and precast pile sizes are found to be (1 to 2) %, (1.25 to 1.75) %, and (27 to 36) %, respectively. In addition, the maximum axial force increment rate is found to be 0.47% for precast pile sizes of 400 × 400 and 450 × 450 mm.