Abstract
Soils with highly gypsum content signify known as soils that exhibit collapsibility and sudden failure when being submerged to wetting. Many of the constructions built on this soil showed cracked and/or collapsed at some parts as these soils immersed or leached with water. The utilization of extremely fine materials, for example, Microscale or Nanoscale, is generally utilized these days. This research compared the use of Silica fume (SF) (micro material) and Nano Silica fume (NSF) (Nanomaterial) to explore the capability of these very fine materials to mend the shear strength and collapsibility properties of highly gypseous soils. The soil as Poorly Graded Sand (SP) was used, with a gypsum amount equal to 62%. A succession of direct shear tests and double odometer tests were carried on dry and submarined specimens of soil at various percentages of SF and NSF. The obtained results indicate that mixing the highly gypseous soils with SF or NSF improved the engineering properties of these soils, especially for the wet condition. The average increment in apparent cohesion when adding SF (5-20) percentage varies between (140-310) % in dry soil and (20-40) % in soaked soil. Same results obtained when mixing the gypseous soils with (1-5) % of NSF. Also, the Nanomaterial provided an improvement of the friction angle in dry and submerged cases respectively. Considering that, the SF gives adverse results upon the friction angle of the soil. The SF and the NSF both condensed the dangers of gypseous soil collapsibility. Consequently, the use of NSF can be assertively suggested to improve the engineering characteristics of highly gypseous soils when compared with SF, where only mixing of 3% of NSF gives the best results.
Highlights
Some soils are often relatively hard and suffer small deformation under normal foundation loads
The physical implies that the soil properties are improved by utilizing mechanical methods, for example, compaction, stone columns, pre-wetting, dynamic compaction, and so on, [5], while the chemical improvement methods means that the soil characteristics are improved with some chemical additives, such as chloride, dehydrate calcium, lime, cement, bentonite, cutback asphalt, etc. [6], [7], Whereas the synthetic improvement implies that the soil properties are improved with some added substances, for example, dried out calcium chloride, concrete, lime, bentonite, reduced black-top, and so on
The Silica content was used in four trails (5, 10, 15, and 20) %; the results show the increment of unconfined compression strength (UCS) as an increase of Silica fume (SF) percentage until 15% after that UCS is decreased
Summary
Some soils are often relatively hard and suffer small deformation under normal foundation loads. Soils with high gypsum content can be considered as collapsible soil These soils distribution covers about 18% of the United States, 16% of Europe, 15% of Russia and Siberia, and twenty percent of the total area of Iraq. Instances of collapsibility of gypseous soils and loosening of shear strength had been documented extensively in many parts of the world. These cases are typically associated with saturation of soil by water, broken pipe water, another kind of artificial flooding from the land, or upward water saturation from perched water, [3] [4]. The physical implies that the soil properties are improved by utilizing mechanical methods, for example, compaction, stone columns, pre-wetting, dynamic compaction, and so on, [5], while the chemical improvement methods means that the soil characteristics are improved with some chemical additives, such as chloride, dehydrate calcium, lime, cement, bentonite, cutback asphalt, etc. [6], [7], Whereas the synthetic improvement implies that the soil properties are improved with some added substances, for example, dried out calcium chloride, concrete, lime, bentonite, reduced black-top, and so on
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