الفهرس 
ABSTRACT
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Abstract
In more recent times the population in Egypt went to get out of the narrow valley on the banks of the river Nile to the development of the desert. Some types of desert soil causing problems clearly among these types of collapsible soil. The Problematic soil has been given a great attention by geotechnical engineers and researchers. In general, all of the soils, which may be encountered with some type of damages or difficulty due to the construction of new structures or utilizing existing structures, could be classified as problematic soils. The Problematic soil is found in different shapes such as collapsible. The soil chosen in this research was extracted from a site in Edfu- Aswan, Egypt. These soils have caused many problems in this region and due to the development in water and sewage lines, which led to settlement and cracks in buildings.The main objective of this study is to investigate the effect of blending of collapsible soil with Silica fume (SF) on its engineering properties. SF. Silica fume is a mineral composed of ultra – fine solid, amorphous glassy spheres of silicon dioxide (SiO2) from the metallurgical industries company (E.JS.C) in Edfu.
A series of laboratory experiments had been implemented for samples prepared with different percentage of SF 1%, 3%, 5%, 7%, and 9%. The results show that the blend with silica fume diminishes the collapsible potential. Liquid limits and Plasticity Index decrease with the increase of silica fume content.The unconfined compression strength increases from 1.57 to 2.37 kg / cm2 when mixing with SF ratios of 0 to 9%, prepared at optimum moisture content at zero days.The increase in the unconfined compression strength continued consistently for curing times of 7, 14, and 28 days.The increase in the unconfined compression strength is attributed to the internal friction of silica fume particles and chemical reaction between silica fume and soil. An increase in silica fume content in soil has made the stabilized soil samples more brittle than the natural soil samples, which is the ductile one as compared to all the stabilized samples.
Their max dry density would increase from 1.92 to 2.02 gm/ cm3 at an SF ratio 0 to 9% and the optimum moisture content increased as well from 21.33% to 27.25% at an SF ratio 0 to 9%. At SF, 0-9% due to the fact that silica fume works as a filler material fills the voids in the soil matrix. Thus, - results indicated that by blending Silica Fume and collapsible soil together, the engineering properties of collapsible soils can be enhanced.
Silica fume is a highly effective a pozzolanic material (silicon dioxide, SiO2) reacts with clay minerals of the soil such as aluminum oxide, Al2O3 and produces aluminum-silicate hydrate cement (cemented material) with soil particles.Adding more than 5% silica fume to the collapsible soil had an insignificant effect on the properties of collapsible soil