[Show abstract][Hide abstract] ABSTRACT: Bida Basin is located in the central part of Nigeria, trending northwest southeast. Present study is focused on the claystone units of the Maastrichtian Patti and Enagi Formations in southern and northern Bida Basins respectively, to determine the paleoenvironments, geochemical and geotechnical properties and, assess the economic potential of the clay deposits. At Share, towards the middle part of the Enagi Formation section, cream to white claystone beds are interbedded with cross to parallel stratified quartzarenitic sandstones. In the Patti Formation section at Agbaja, white, massive claystone beds are interbedded with herringbone and hummocky cross stratified sandstones. Gross sedimentological features suggest that the associated sandstone facies were deposited in tidal channel to shoreface environments whereas the claystone probably represent a low energy floodplain sub environment. Geochemical data show that the claystone at Share is composed of SiO 2 content ranging from 45.2% to 64.8% (average of 58.1%) while at Agbaja, the values range from 48.5% to 74.7% (average of 63.3%). Al 2 O 3 value for the clay at Share ranges from 20.3% to 37.9% (averaging 26.9%) while, the Agbaja samples is between 15.61% and 34.23% with an average of 24.6%. These indicate that the clays are essentially hydrated siliceous aluminosilicates. Relatively low abundance of MgO and K 2 O (less than 0.30%) indicate lack of expandable clay mineral in the samples. Plastic limit less than 30% indicates that clays are kaolinitic. Average Plastic Index for the Share and Agbaja clays are 24.29 and 17.7% respectively and the shrinkage limit values (average) are 10.05% and 2.66%. The clays compare favourably with the Plastic fire clay of St. Louis and Florida active kaolinite. Their characteristics are quite consistent with other sedimentary kaolin deposits in Nigeria. They also show low heavy metal concentrations and thus may be beneficiated and suitable as raw materials for ceramic, pharmaceuticals and paints.
[Show abstract][Hide abstract] ABSTRACT: Enhancing the quality of granular layers is fundamental to optimise the structural performance of the pavements. The objective of this study is to investigate whether previously developed packing theory-based aggregate parameters can evaluate the resilient modulus of unbound granular materials. In this study, 19 differently graded unbound granular materials from two countries (USA and Sweden) were evaluated. This study validated both porosity of primary structure (PS) and contact points per particle (coordination number) as key parameters for evaluating the resilient modulus of unbound granular materials. This study showed that decreasing the PS porosity – higher coordination number – calculated based on the proposed gradation model, yields higher resilient modulus. Good correlation was observed between the proposed packing parameters and resilient modulus of several types of aggregates. The packing theory-based framework successfully recognised granular materials that exhibited poor performance in terms of resilient modulus.
Keywords: unbound materials; packing theory; primary structure; porosity; coordination number; resilient modulus
International Journal of Pavement Engineering 10/2013; · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The maximum height for the salt pile in a circular dome with a 4ft retaining wall was determined by two methods. The first method used rigid-body physics; in this model, the critical angel, the maximum angle of inclination allowed while maintaining static equilibrium, was determined using only the external coefficient of friction for salt. Because the static equilibrium also depended upon internal friction, a second model was developed. Development of the second model utilized particle physics, fluid mechanics and soil stress analysis. Mohr's circle, the internal coefficient of friction for salt and its angle of repose were used to determine the critical angle. These results were combined to form our solution model, Model II, which consisted of two submodels:Model II(a) provides a general solution where the front-end loader is allowed to freely travel to any location on the salt pile. This model yields a maximum height of 17.4ft for a symmetric cone with a critical angle of 14.6°.Model II(b) provides a volume-maximizing solution if the loader's travel is restricted. This model yields a maximum height of 23.7ft for a wedge shape with a ramp slope of 14.6° and a back edge slope of 35.9°, where the loader must not cross the peak.Therefore, the authors recommend that Model II(a) be used in the general situation, since the loader is allowed to drive anywhere on the salt pile in this case. When the maximum volume provided is insufficient, Model II(b) can be utilized to increase the capacity of the dome. (Note: The loader must not cross the peak in this model.)
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