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GEOLOGICAL REPORT OF PDP SITE BY ESANG VICTOR WILLIAMS IT STUDENT FROM FUTMINNA, DEPARTMENT OF GEOLOGY TO THE PROJECT MANAGER BOUYGUES NIGERIA LTD PDP NATIONAL SECRETARIATE COMPLEX SITE ABUJA, F.C.T NOVEMBER 2010 1 TABLE OF CONTENT TITLE PAGE INTRODUCTION……………………………………………………………………….. 2 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 LOCATION……………………………………………………………………….. 3 GEOLOGY OF THE AREA…………………………………………………… 3 METHOD EMPLOYED………………………………………………………. 3 SOIL…………………………………………………………………………………. 3 THICK LATERITIC SOIL………………………………………………………. 3 DESCRIPTION…………………………………………………………………… 4 USES………………………………………………………………………………… 4 CONCLUSION AND RECOMMENDATION………………………….. 5 REFFERENCES…………………………………………………………………… 6 2 INTRODUCTION The objectives of this geological report is to provide the composition, behavior and usefulness of the excavated soil from the site. This report gives in details information about the soil type. The role of a geologist in soil analysis is to provide details about the origin and history of the rock and soil of a particular area, and to give advice on how to cope with the behavior of the soil, for the safety of whatever structure or construction that would be sited on a particular area. It also includes: The evaluation of earth material for construction purpose and evaluation of waste disposal and hazardous waste on site. Also to help the engineering geologist supply the site engineer with geological info and insures that the geological factors are properly considered. Finally, note that this geological report is not the same as the soil test rather it is aimed at unveiling the usefulness of the excavated soil on the site. 3 1.2 LOCATION The area mapped is located in plot number 243 cadastral zone A00 central business area district, Abuja. The global positioning system is 09 ° 03.000 'north, 007° 29.026' east. 1.3 GEOLOGY OF THE AREA The area is basically underlain by rocks of Precambrian basement complex, comprising mainly of biotite-hornblende granite. The mapped area is covered by thick lateritic soil and traces of kaolin clay soil and no visible outcrops. 1.4 METHOD EMPLOYED The absence of outcrop means that the use of compass clinometer Would not be necessary and the grain size of the soil are visible to the human eyes. Therefore it is described with it physical appearance and it mineralogical composition through geological research and transverse method was used during this mapping exercise. 1.5 SOIL Soil have been defined in different ways according to the field they involved. Generally we can define it as the upper layer of the earth in which plant grows. In engineering, soil is either naturally occurring or man-made and 4 distinguished from rocks because the individual particle is not sufficient bonded together. while in engineering geology, soil is refer to as the entire unconsolidated material that overlies and distinguish it from it’s bed rocks. Finally, it can also be said to be a naturally conclomeration of mineral grains ranging from large borders to single mineral crystal of Microscopic size. 1.6 THICK LATERITIC SOIL This is a red residual surface soil formation rich in iron and aluminum, formed by the leaching of silica, especially in hot and wet tropical areas, developed by intensive and long lasting weathering of the underlying parent rock. Lateritic soil is also said to be a product of a long prolonged process of mechanical and chemical weathering which produces a wide varieties in the thickness grade, chemistry and all the mineralogy of the resulting soil. Nearly all lateritic soil are rusty-red because of its iron oxide content. Lateritic soil are found to be thick on the stable area of the Africa shield. Thick lateritic soil can either be soft or easily broken into smaller pieces of firm and physically resistant. Basement rocks are buried under 5 thick weathered layer and seldom expose. Lateritic soil forms the uppermost soil of the lateritic cover. Lateritic soil may contain clay mineral but tend to be silica-poor because silica is leach out by water passing through the spoil. Typical lateritic soil is porous and clay-like. There are some traces of with colored grain in the area which are known as kaolinite, a product of alteration of feldspar in granite due to chemical weathering. It is one of the popularly known member of clay minerals. 1.7 DESCRIPTION • Chemical composition Chemical composition of laterite depends on their parent rock and They include quartz SiO₂, iron oxide minerals: goethite HFeO₂, Titanium Oxide, Zircon, Iron, Tin Lepidocrocite FeO (OH), Heamatite Fe₂O₃ and hydrated oxides: Aluminum or Gibbsite Al₂O₃.3H₂O. • Specific Gravity: 2 • Hardness: 1.5-2 • Colour: Blackish-brown to reddish brown. • Appearance: Red, Yellow and Brown when fresh. • Texture: fine grained. 6 1.8 USES i. Building blocks: that is normally refered to as red bricks. ii. Building construction: It has been prove in the past that not all soil is suitable for foundation of structures especially clay for a long period of time. Lateritic soil is used to fill such site before the commencement of any foundation work. One good example of this is the present work at B.O.B (Body Of Benchers) site. iii Road Construction: Lateritic soil is recently taking the place of stone base in road construction, in other not waste resources and energy. Lateritic soil is used as a sub-base during road construction before the Hard course material is applied to it, and this act prevents pot holes because when ordinary clay soil is used especially montmorillonite it can lead to shrinkage and expansion during the hot and wet seasons. Iv. Acts like an aquifer : thick laterite layer is porous and slightly Permeable, an aquifer is a geological formation capable of holding Substantial quantity of water that can be drilled out for human consumption. 7 v. Waste treatment: it can be used for the phosphorous and heavy metals at several sewage facilities up to 99%. Percolating columns of laterite remove enough Cadmium, Chromium and this can lead to undetectable concentration at a low cost and technology, efficient for rural areas. vi. Ore: Laterite acts as ore for bauxite, Iron Nickel. An Ore can be a metaliferrous geologic formation from which metal of great importance can be extracted from as listed above. Its has known to be the earliest ore for Nickel and currently account for about 40% of the world Nickel. 8 CONCLUSION AND RECOMMENDATION Base on the mapping carried out on the plot number 243 cadastral zone A00 central business district F.C.T Abuja and the nature of geological data at or near the surface area, it is thus deduce that the formation is a hard rock terrain covered by thick lateritic soil and traces of whitish kaolinite member group of clay mineral. Thus the excavated thick lateritic soil from the mapped area should not be taken as waste but as an important economic construction material which can also act as an economic material especially for brick industry. 9 Fig : Picture Showing Foundation On Lateritic Soil SOURCE: BNL CONSTRUCTION AND ENGINEERING 2010 (PDP SITE 10 REFFERENCES 1. 2. 3. 4. CIE315 Course Materials. Google Geology of Nigeria. Minerallogy. 11