Some Hydraulic, Mechanical, and Physical Characteristics of Three Types of Compressed Earth Blocks

Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 8 (2006): Some Hydraulic, Mechanical, and Physical Characteristics of Three Types of Compressed Earth Blocks. Manuscript BC 06 007. Vol. VIII. August, 2006

3D settlement analysis of underpinning piles under raft foundation subjected to nonuniform vertical loading

Existing rafts under the design loads sometimes experience excessive settlements or confront such a possibility in the future if the modified functionality of building is induced to increase the foundation loading. Differential settlement and deflection may also be observed in case of eccentric loading especially when these structures are built on soft soils. One of such precedents was observed in a silo structure used as a cement plant located in Douala, Cameroon. The structure that is founded on deep, soft clay with high ground water table rests on a raft supporting the storage tanks located at one side of the building conveying non-uniform loading to the existing raft. In one and a half year after completion of the construction, the silo structure had significantly settled and deflected. The underpinning pile remediation system allowing the continuity of cement production is applied from the outside of building using the rigidly connected protruding reinforced concrete section as a capping beam. In this study, the entire foundation system is numerically analyzed using the presented 3D finite element (FE) models. The back-analyses are used for the calibration concurring with the actual measurements of settlement and deflection at the site. The foundation systems with and without the underpinning piles are compared with each other to reveal how the remedial improvement is achieved by the presented underpinning pile system

Contrasted mineralogical composition of the laterite cover on serpentinites of Nkamouna-Kongo, southeast Cameroon

AbstractFour drill cores along a lateritic hill in Nkamouna-Kongo (southeast Cameroon) were studied using microprobe analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and infrared spectroscopy. The main objective of the study was to investigate the occurrence of clay silicates while evaluating the Ni-Co content of the laterite for potential mineral exploitation. The thick lateritic profiles (&gt;40 m deep) developed on serpentinized ultramafic rocks have an Fe-rich clayey fraction, with goethite as the main mineralogical constituent and secondary quartz and relicts of magnetite-maghemite as accessory minerals. Silicate clays are less abundant and occur mainly towards the top of the profiles. At the summit of the interfluve, kaolinite and some gibbsite are associated with goethite. Along the slopes, at the bottom of profiles, the weathered bedrock shows the presence of smectite (Fe-beidellite) and kaolinite, probably due to slower water-flow conditions. Towards the top of the profile in the lower clay, ferruginous and upper clay horizons, only kaolinite remains with gibbsite, after the leaching of silica and soluble cations following repeated remobilization-recrystallization processes. At the summit, where the downward movement of water is rapid, no smectite was identified. As a whole, the mineralogical composition of the material varies in close relationship with the drainage, leading to a contrasted clay mineralogy marked by the presence of Fe-beidellite and kaolinite at the bottom, and that of kaolinite and gibbsite at the summit of the profiles.</jats:p

Genesis of Meka’a Geophagic Kaolin Deposit (In Foreke-Dschang West Cameroon)

Geological, mineralogical and geochemical studies where carried out on Meka’a kaolin deposit located in Foréké-Dschang in order to define the ore genesis. Three kaolin facies (yellow, red and white) and isalteritic components were characterized by different methods including morphostructural description, XRD, XRF, ICP-MS, SEM-EDS, heavy mineral research and organic matter contents. The results show that all these kaolins are based on kaolinite (87–90%) associated with more or less significant phases of orthoclase (1-2%), goethite (0.5-3.5%), quartz (1-1.5%), anatase (1.2-2%) and hematite (1-2%). Small amounts of illite (3.5%) was found only in white facies. The scanning electron microscope (SEM) pattern shows that kaolinite particles contained in these kaolins are very small (&lt;2 µm) and are poorly crystallized due to the impurities they contain. Meka’a kaolin’s are extremely weathered (CIA and CIW ≈ 100) and their organic matter content is considerable (1.82-2.54%) and is explained by the presence of carbonized wood in the ignimbrites. The combination of different analytical techniques points out a meteoric weathering of ignimbrite under oxidizing conditions as being of petrogenetic origin of this kaolin deposit.</jats:p

Geomechanical characterization of lateritic hardpans from Bamendjou (West-Cameroon)

AbstractThis study reports on the physical, mechanical, mineralogical and geochemical analysis carried out on four lateritic hardpan specimens from quarries in the Bamendjou area in the Western Region of Cameroon using common prescribed procedures. The results indicate that values of the bulk density, specific gravity, total and open porosities are very variable from one specimen to another. Meanwhile, the value of the compressive strengths of both the dry and immersed specimens were also very variable from one specimen to another, with the F2 and F1 specimens having higher values than the A1 and A2 specimens. All the specimens immersed in water recorded lower compressive strengths than the dry specimens. The flexural strengths also varied from one sample to another, with the F2 specimen having the highest resistance. The X-ray diffraction patterns reveal that the major peaks were assigned to gibbsite, goethite, and hematite, while the minor peaks were assigned to kaolinite and anatase. The mineralogy and geochemistry influenced the physical and mechanical properties, with the iron rich specimens having higher values in both the physical and mechanical properties than the alumina rich specimens. The results of the compressive strengths obtained were higher than (1–4) MPa obtained in Burkina Faso and India where they have been using latertic blocks for construction. Thus the hardpans of Bamendjou can also be exploited for building purposes conveniently.</jats:p

Ceramic with potential application of ngwenfon alluvial clays (noun, west cameroon) in building construction: Mineralogy, physicochemical composition and thermal behaviour

Our aim is to characterize four types of alluvial clays from the locality of Ngwenfon situated 35 km from Foumban (West Cameroon). X-ray diffraction, thermal analysis, chemical composition, particle size distribution, organic matter content and plasticity were investigated in raw clay materials in order to determine their suitability for building material and firing bricks in particular. Ceramics properties such as linear shrinkage, water absorption, flexural strength, compressive strength, bulk density and mineral neoformations were also investigated by firing specimen bricks at a temperature range of 800 °C–1150 °C. Kaolinite, quartz, goethite, feldspar and illite represent the dominant mineral phases, in addition to minor quantities of chlorite, gibbsite, anatase and plagioclase. The main oxides are; SiO2, Al2O3, and Fe2O3. The physical parameters of the alluvial clays display a continuous and various particles size with a relatively high plastic index (12%–36%) and high organic matter contents (9%–13%). A significant densification has been observed at a temperature of 1150 °C. This was confirmed by the appearance of new mineral phases such as mullite, cristobalite and spinel, which are responsible for the increased mechanical strength and a reduction in water absorption. Most of the alluvial clays from Ngwenfon display suitable ceramic properties at sintering range from 1000 °C to 1150 °C. However, the black clays, with low ceramic properties at temperatures of 1150 °C, are inappropriate for fired brick production. These black clays are characterized by a compressive strength lower than the required value of 20 MPa for the standard reference. © 2018 Elsevier LtdCharacterisation et valorisation des argiles de Foumban (Ouest Cameroun