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Materials Sciences and Applications 2021年第6期12卷 263-275页

作者： Ferland Ngoro-Elenga Atipo Itoua Ngopoh Hilaire Elenga jean-romuald mambou Jude Novelgi Ngakosso Ngolo Timothée Nsongo Faculté des Sciences et Techniques Université Marien Ngouabi Brazzaville Congo Groupe de Recherches sur les Propriétés Physico-chimiques et Minéralogiques des Matériaux Université Marien Ngouabi Brazzaville Congo Centre de Recherches Géologiques et Minières Brazzaville Congo

In this work, the authors made aquatic filters according to the formulation “clay stabilized at 4% of cement mixed with 4% of kambala sawdust and 10% of white sand” then heated to 1050°C to decontaminate the waters of gutters and wells. The authors carried out geotechnical, geochemical, thermal, infrared spectroscopy, and scanning electron microscopy that analyzed the clay material. Geotechnical analyzes have shown that this material is made up of 22% thin sand, 22% of silt, and 56% of clay with 26 plasticity index. The geochemical analysis showed the presence of trace elements shared out as follows: 3% of alkaline metals, 24% of alkaline earth metals, 46% of transition metals, 10% of metal, 16% of lanthanides, 1% of actinides. The most abundant trace elements are barium (19%), vanadium (12%), chromium (11%) and zinc (9%). The thermal and microscopic analyzes revealed the kaolinitic nature of materials. The chemical depollution studies have shown elimination yields of 50% - 52.38% of sulphates;77.33% - 85.19% of phosphates;34.85% - 88.49% nitrates;91.3 - 100 of sulphides;The removal of bacteriological pollution are 92.8% - 98% of total germs;94% - 97% of total coliform and 95% - 98% of E. coli.

关键词： Clay Characterization Chemical Depollution Bacteriological Depollution Gutter and Well Water Makoua

Redistribution and magnitude of stresses around horse shoe and circular excavations opened in anisotropic rock

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International Journal of Mining Science and Technology 2015年第4期25卷 615-621页

作者： mambou Ngueyep Luc Leroy Ndop Joseph Ndjaka jean-Marie Bienvenu Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundéré Douala Institute of Technology

In this paper numerical analysis of underground structures, taking account the transverse isotropy system of rocks, was done using CAST 3M code by varying the shape of excavation and the coefficient of earth pressure k. Numerical results reveal that the anisotropy behavior, the shape of hole and the coefficient of earth pressure k have significant influence to the mining induced stress field and rock deformations which directly control the stability of underground excavation design. The magnitude of horizontal stress obtained for the horse shoe shape excavation(25.2 MPa for k = 1; 52.7 MPa for k = 2)is lower than the magnitude obtained for circular hole(26.4 MPa for k = 1; 59.5 MPa for k = 2).Therefore, we have concluded that the horse shoe shape offers the best stability and the best design for engineer. The anisotropy system presented by rock mass can also influence the redistribution of stresses around hole opened. Numerical results have revealed that the magnitude of redistribution of horizontal stresses obtained for transverse isotropic rock(12.1 MPa for k = 0.5; 25.2 MPa for k = 1 and52.7 MPa for k = 2) is less than those obtained in the case of isotropic rock(27.6 MPa for k = 1;48.6 MPa for k = 2 and 90.81 MPa for k = 2). The more the rock has the anisotropic behavior, the more the mass of rock around the tunnel is stable.

关键词： Horse shoe excavation Stress Strain Transverse isotropy Finite element

Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第1期7卷 101-108页

作者： Luc Leroy Ngueyep. mambou Joseph Ndop jean-Marie Bienvenu Ndjaka Laboratory of Sciences Material Department of Physics Faculty of Science University of Yaounde Yaounde Cameroon Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundere Meiganga Cameroon Douala Institute of Technology Douala Cameroon

The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton＇s second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the me- chanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 ~C to 500 ~C, the internal stress and internal strain are weak; whereas above 500 ~C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

关键词： Granite rock specimenHigh temperatureInternal stressInternal strainISO 834 fire

Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

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岩石力学与工程学报 2015年第1期34卷 101-108页

作者： Luc Leroy Ngueyep.mambou Joseph Ndop jean-Marie Bienvenu Ndjaka Laboratory of Sciences Material Department of PhysicsFaculty of ScienceUniversity of Yaoundé Department of Mine Mineral Processing and EnvironmentSchool of Geology and Mining EngineeringUniversity of Ngaoundéré Douala Institute of Technology

The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton's second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the mechanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 C to 500 C, the internal stress and internal strain are weak; whereas above 500 C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fi re reduces the mechanical performance of granite signi fi cantly. Moreover, it is found that after 3 min of exposure to fi re,the mechanical energy necessary to fragment the granite can be reduced up to 80%.

关键词： Granite rock specimen High temperature Internal stress Internal strain ISO 834 fire

Sedimentology and Mineralogy of Surface Formations of the Mossendjo Area (Republic of Congo): Paleoenvironmental and Paleoclimatic Implications

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Open Journal of Geology 2021年第10期11卷 471-493页

作者： Jude Nogelvi Ngakosso Ngolo Hilaire Elenga mambou jean romuald Malounguila Ganga Dieudonné Malanda Edmond Laboratory of Geosciences Faculty of Science and Technology Marien Ngouabi University Brazzaville Congo Geological and Mineral Research Center (CRGM) Brazzaville Congo

Studies undertaken at several sites in the Congolese basin and in the Chaillu massif are helping to reinterpret the sedimentological formations known as cover formations, which are widely exposed in Central Africa. This article presents the results of granulometric, morphoscopic, mineralogical and chemical analyzes obtained at three sites in the Chaillu. Gronulometric analysis indicates that the sands at the three sites are rated medium to high. The cumulative curves are essentially sigmoidal with regular and spreading slopes. This facies indicates that the deposition took place due to a banal and moderate variation in the competence of the carrier current. The morphoscopy of the quartz grains shows that they are mainly angular and shiny. These data reflect a relatively close source and transport by water. The synthesis of lithological, granulometric, petrographic and geochemical analyzes allowed us to highlight three episodes of deposits in the Mossendjo area: the first is characterized by a channel-type fluvial system marked by deposits from the hospital borehole and from the station;the second, which is alluvial, corresponds to the clogging of the channel. These two alluvial phases are overcome by a third, fluvial, channel-type episode, the end of which is marked by the establishment of the yellow formation. The vertical and lateral organization at the outcrop of this yellow formation has the same characteristics as those described earlier and in the sub-region where it was attributed to the wind-generated cover formation. This study thus highlights the existence of a wet phase during which two fluvial systems of non-contemporary channel types developed which overlap.

关键词： Sedimentology Fluvial System Paleoenvironment Mossendjo Congo

Displacements, Strains, and Stresses Investigations in an Inhomogeneous Rotating Hollow Cylinder Made of Functionally Graded Materials under an Axisymmetric Radial Loading

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World Journal of Mechanics 2018年第3期8卷 59-72页

作者： Elise Rose Atangana Nkene Luc Leroy mambou Ngueyep Joseph Ndop Emma Sandring Djiokeng jean-Marie Bienvenu Ndjaka Department of Physics Faculty of Sciences University of Douala Douala Cameroon Douala Institute of Technology Douala Cameroon Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon Department of Mine Mineral Processing and Environment School of Geology and Mining Engineering University of Ngaoundéré Meiganga Cameroon

In this paper, an analytical and numerical study of strain fields, stress fields and displacements in a rotating hollow cylinder, whose walls were completely made in Functionally Graded Materials (FGM), was conducted. We have considered the rotating hollow cylinder submitted to an asymmetric radial loading. It is assumed that, because of the functional graduation of the material, the mechanical properties such as Young elastic modulus and the density varies in the radial direction, in accordance with a the power law function. The inhomogeneity parameter was selected between -1 and 1. On the basis of the second law of Newton, Hooke’s law and the strain-stress relationship, we established the differential equation which governs the equilibrium for a rotating hollow cylinder. We found the analytical solution and compared to the numerical solution obtained by using the shooting method and the fourth order Runge-Kutta algorithm. The analytical and numerical results lead to the conclusion that the magnitude of the tangential stresses is greater than that of the radial stresses. The changes due to the graduation of FGM does not produce consistent variations in the distribution of radial stresses, but strongly affects the distribution of tangential stresses. The tangential stresses, tangential strains and displacements are much higher at the inner surface of the cylinder wall. The internal radial pressure intensely affects the radial stresses and the radial strain.

关键词： Functionally Graded Materials Radial Stresses Tangential Stresses Cylinder Wall

Density and Strength of Mortar Made with the Mixture of Wood Ash, Crushed Gneiss and River Sand as Fine Aggregate

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Journal of Materials Science and Chemical Engineering 2018年第4期6卷 109-120页

作者： mambou Ngueyep Luc Leroy Keyangue Tchouata Jules Hermann Atangana Nkene Elise Rose Ndop Joseph Fotseu Miyo Christian Dupont Ndjaka jean-Marie Bienvenu Laboratory of Material Sciences Department of Physics Faculty of Sciences University of Yaoundé 1 Yaoundé Cameroon School of Geology and Mining Engineering University of Ngaoundéré Meiganga Cameroon Douala Institute of Technology Douala Cameroon Department of Physics Faculty of Sciences University of Douala Douala Cameroon

The main purpose of this paper is to study the feasibility of using wood bottom ash to partially replace natural fine aggregate or crushed gneiss sand in the manufacturing of mortars. The experiment uses wood ash as fine aggregates, which passes through 5 mm sieve, in proportions of 5%, 10%, 15%, 20% and 25% by weight to replace partially river sand and crushed gneiss, and the both sand of the same size as the aggregate respectively. Experimental results show that density of mortar and the compressive strength of mortar decrease globally with the increase in wood ash content. At 56 days, and for all replacements with wood ash, compressive strengths values of mortar obtained with the mixture of wood ash and river sand is greater than 20 MPa, which is not the case for mortar made with crushed gneiss and wood ash. Moreover, for 5% of replacement with wood ash, compressive strengths of mortar obtained with the mixture of wood ash and river sand and the mixture of wood ash and crushed gneiss are respectively 37 MPa and 32 MPa at 56 days. These values satisfied the strength requirements. Hence, 5% replacement of crushed gneiss with wood ash is suggested and could be benefit for mortar. In addition, the replacement of sand by wood ash is preferable with river sand which contains fewer fines than crushed gneiss. The compressive strength of mortar with 25% wood ash + river sand could be suitable.

关键词： Wood Bottom Ash River Sand Crushed Gneiss Mortar Compressive Strength Density

Sedimentology and Mineralogy of Surface Formations of the Mossendjo Area (Republic of Congo): Paleoenvironmental and Paleoclimatic Implications

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