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Oluseun Adetola Sanuade, Abayomi Adesola Olaojo, Adesoji Olumayowa Akanji, Michael Adeyinka Oladunjoye and Gabriel E. Omolaiye

Abstract

This geophysical study was carried out to determine the occurrence of phosphate nodules in the Oshoshun Formation of the Dahomey Basin, Southwestern Nigeria. The electrical resistivity method, comprising 1D vertical electrical sounding (VES; using Schlumberger array) and 2D geoelectrical imaging (using Wenner array), was used to determine the nature and depth of occurrence of the phosphate nodules. Six profile lines were established within the study area, and inverted sections were generated from the apparent resistivity data using DIPRO inversion algorithm. Five VES points were also acquired in the study area, and Win-Resist programme was used to process and interpret the field resistivity data. Four pits were dug along the profiles to verify the interpreted results. The results obtained by both techniques reveal similar geoelectric units: the top soil, clay, clayey sand and clay at different depths. These layers host pockets of phosphate nodules (78–≥651 Ωm) with varying thicknesses. The strong correlation between the lithology profiles obtained from the pits and the interpreted results of the inverted apparent resistivity sections demonstrates the efficacy of the electrical resistivity method in characterising phosphate occurrence within the formation.

Open access

Oluseun Adetola Sanuade, Akindeji Opeyemi Fajana, Abayomi Adesola Olaojo, Kehinde David Oyeyemi and Joel Olayide Amosun

Abstract

A geostatistical approach was used to model porosity of OBA field in onshore area of Niger Delta using simulation technique. The objective is to understand the spatial distribution of porosity and characterize the degree of heterogeneity of underlying formation. Porosity data from twenty-two wells were loaded into SGeMS software. Univariate statistical analysis, experimental semivariogram and Sequential Gaussian Simulation (SGS) were applied on the data. The data was close to normal approximation of Gaussian based of the results of univariate statistics. However, to construct and model horizontal and vertical semivariograms, the data was log-normalized to reduce the coefficient of variation and to get good fit of the model. Parametric semivariogram model shows the range of 72–6480 m, nugget effect of 0.006 and sills of 0.0095, 0.0099 and 0.0111. Six realizations were generated using SGS algorithm and the results suggest that any one of the realizations can independently represents the true picture of the subsurface geology within the study area. Ranking of realizations shows realization 6 as the best and realization 2 as the lowest. This model could

Open access

A. M. Abd-Elnaiem, M. Mohamed, R. M. Hassan, M. A. Abdel-Rahim, A. A. Abu-Sehly and M. M. Hafiz

Abstract

Effect of annealing temperature on the structural and optical properties of As30Te60Ga10 thin film was studied using various techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSC analysis revealed that the As30Te60Ga10 glass has a single glass transition and crystallization peak while XRD results confirmed that the as-prepared and annealed films have crystalline nature. The coexistence of the crystalline phases in the investigated films could be attributed to the formation of orthorhombic As, hexagonal Ga7Te10, and monoclinic As2Te3 phases. It was found that the average crystallite size and optical parameters of the studied films depend on the annealing temperature. For example, the optical band gap decreased from 1.54 eV to 1.11 eV as the annealing temperature increased from 300 K to 433 K.

Open access

A. J. Nagajothi, R. Kannan and S. Rajashabala

Abstract

Chitosan has been successfully incorporated as a filler in a polyethylene oxide (PEO) and lithium trifluoromethanesulfonate (LiCF3SO3) matrix with a combination of plasticizers, namely 1,3-dioxolane (DIOX) and tetraethylene glycol dimethylether (TEGDME). The composite gel-polymer electrolyte (CGPE) membranes were prepared by solution casting technique in an argon atmosphere. The prepared membranes were subjected to SEM, TG/DTA and FT-IR analyses. A Li/CGPE/Li symmetric cell was assembled and the variation of interfacial resistance was measured as a function of time. The lithium transference number (Li+ 1 ) was measured and the value was calculated as 0.6 which is sufficient for battery applications. The electrochemical stability window of the sample was studied by linear sweep voltammetry and the polymer electrolyte was found to be stable up to 5.2 V.

Open access

Marek Grodzicki and Marek Rotkegel

Abstract

The article presents a comparison of the roadway supports currently used in mines in the Soma basin in Turkey with new one proposed by Huta Łabędy and Central Mining Institute (GIG) in terms of resistance parameters and work in conditions of specific loads. The strength analysis of the frame was carried out using the finite element method, using the COSMOS/M program, based on the methodology developed and applied in GIG.

The frame models were built corresponding to their geometry and cross-sectional parameters of the sections used. Beam elements (BEAM3D) were used for building models, which were given cross-sectional parameters of the V36 section. This resulted in three frame models that were loaded in three ways (three load variants). The first option included roof load, acting on the roof bar in a uniform manner, at a length of about 3.0 m. In the second variant, the same load was adopted but the resistance of the side wall was omitted. However, in the third variant, the same roof load was assumed in addition to a side load, acting on the sliding arch, at a length of about 3.0 m, a value corresponding to half the load of the roof. As a result of the calculations carried out, the distribution of reduced stresses in the analysed frames and the maximum load values were obtained.

The proposed roadway supports retain the functionality of the previously used frames in terms of width, height, cross-sectional area of the support and the number of elements. They are characterised by the same weight and at the same time, they have up to 24% more load capacity because of the replacement of straight sections of curved side sections. This treatment was possible by forming individual elements of the arch with two bending radii. The additional load increase was obtained by using S550W steel.

Open access

Krzysztof Sternik and Katarzyna Dołżyk-Szypcio

Abstract

Calculation of pullout capacity of anchoring concrete cylindrical block by finite element method is carried out. 3D model of the block assumes its free rotation. Alternative solutions with one and two pulling forces attached at different heights of the block are considered. Dependency of the ultimate pulling force on the points of its application, the block’s embedment depth as well as contact friction are investigated. Results of FE analysis and simple engineering estimations are compared. The maximum pullout resistance results from FE analysis when the rotation of the block is prevented.

Open access

Tomasz Strzelecki, Anna Uciechowska-Grakowicz, Michał Strzelecki, Eugeniusz Sawicki and Łukasz Maniecki

Abstract

This article presents the results of numerical simulations of seepage through the body of the dam and the reservoir bed. The purpose of this study was to analyse the seepage stability during a flood as well as the impact on seepage stability of the diaphragm wall and gravel columns, on which the dam body is founded in selected segments. Simulations were conducted for three different locations, and the following 3D models of the dum were prepared:

  • a model containing the front and right-bank part of the dam, for which no diaphragm wall, gravel columns and drainage ditch were provided for

  • a model of a segment of the right-bank dam including a diaphragm wall, drainage ditch and gravel columns under the dam (two variants with differing diaphragm wall lengths)

  • a model of the water dam segment accounting for gravel columns and a drainage ditch, but without a diaphragm wall. In the case of founding on gravel columns, the base was modelled as an anisotropic medium in terms of seepage properties, macroscopically equivalent to the actual soil medium.

The numerical model utilises the finite element method. The geometry of the dam and geological substrate was defined in the GIS tools in the form of a 3D model of the terrain and geology of the substrate.

Open access

Zygmunt Meyer and Krzysztof Żarkiewicz

Abstract

This article shows the mathematical method to determine the lateral stress on the shaft and toe resistance of pile using the new approach. The method was originally invented by Meyer and Kowalow for the static load test. The approximation curve was used for the estimation of both settlement curve and toe resistance curve of the pile. The load applied at the head of the pile is balanced by the sum of two components: the resistance under the toe of the pile and the skin friction. Therefore, the settlement curve is compilation of two factors: the skin friction curve and the resistance under toe curve. The analysis was based on the verification of the methods using laboratory experiments, that is, static load tests. The results of the research allowed to determine the relationship between parameters of the Meyer–Kowalow curve. On the basis of the relationships, it was possible to determine the skin friction and the toe resistance of the pile. Mathematical analysis of curve parameters allowed to determine the influence of the toe resistance on the settlement.

Open access

Nikodem Wróbel, Michał Rejek and Grzegorz Królczyk

Abstract

The purpose of this study is to form and test inseparable tight joints, commonly used in the construction of heat exchangers, by crimping operation on designed prototype stand. Crimped joints are made by tools in form of cones with two types of shapes, each of the designed tools have got identical forming angle. This study uses two types of connecting blocks and plates, differing in diameters of hole and flange. Elaboration contains a case study of joints being made by the stand, which in addition to the crimping operations for some cases were glued or brazed. The article presents the features of the formed joints, by examining them by destructive testing: Micrography, tensile strength test, and non-destructive testing: Leakage test. The examined elements have been made of aluminum 6060, which is well suited to indirect or direct operations of forming joints for all kinds of coolers or condensers. Elaborated tests and studies in this study allowed to state, that joining the connection block to plate with the small diameter, was more energy-consuming than in sample sets with bigger diameter, use of glue increasing the strength of the joints by 20%, significant strength increase can be obtained after mechanical clinching with brazing operation or modification of geometrical shape of the jaws

Open access

Łukasz Herezy, Dariusz Janik and Krzysztof Skrzypkowski

Abstract

The study summarises the operating characteristics of the powered roof support (shield) used in an automated plough system. Investigated longwall support units were controlled automatically or by section engineers and positioned in the ‘saw tooth’ configuration with respect to the longwall face (automatic mode) or linear to the face. Shield pressure data have been analysed in order to identify the impacts of particular factors on the pressure increase profiles. The analysis was supported by the Statistica software to determine the statistical significance of isolated factors. Equations governing the leg pressure at the given time instant were derived and the roof stability factor ‘g’ was obtained accordingly, recalling the maximal admissible roof displacement method recommended by the Central Mining Institute (Poland). In the current mining practice, its values are used in monitoring of strata behaviour as indicators of shield-strata interactions, particularly in the context of roof control in longwall mining. It is vital that the method used should be adapted to the actual conditions under which the longwall is operated. In the absence of such adaptations, there will be major discrepancies in results. The conclusions section summarises the current research problems addressed at the Department of Underground Mining, in which the support pressure data in longwall operations are used. The first aspect involves the delineation of deformations of a longwall main gate about 100 m ahead of the face. The second issue addressed involves the risk assessment of roof rock caving or rock sliding in the tail gate. Another aspect involves the standardisation of local conditions to support the methodology of interpreting shield-strata interactions in the context of work safety. These methods are being currently verified in situ.