Keywords

natural gypseous soil –gypsified natural soil -artificial gypsified soil–leaching

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artificial gypsified soil –natural gypsified soil –natural gypseous soils.How to cite this articleW.M.Yaqoob, F.H. Rahiland M.A. Al-Neami, “Characteristics of Artificial, Gypsified and Natural Gypseous Soils under Dry Condition, ”Engineering andTechnologyJournal, Vol. 37, Part A, No. 8, pp. 302-312, 2019.1.IntroductionThe gypseous soils was a collapsibility soil upon wetting because of its unpredicted properties. Gypseous soil introduced several changes in their chemical and physical properties when exposed to water [1]. Gypsum was a type of salts that can be dissolve in water and the particles transported when the leaching process were happen. Gypsum may present in soil as one or combination of the following forms [2]:1.Hydrated gypsum, CaSO4. 2H2O, crystalline form.2.Anhydrite gypsum, CaSO4, crystalline form.3.Al-Baster, non-crystalline form of gypsum. Fine grain –usually massive, light color.4.Secondary gypsum, crystals in surface layers, sometimes crust or re-crystalized from evaporated ground water.Secondary or detritus and pre-precipitated gypsum, crystals in surface layers, sometimes crust or re-crystalized from evaporated ground water.Secondary gypsum which may be formed by, Buringh, 1960 [3]: 1. The primary gypsum rocks dissolved and precipitated in younger formation in both crystalline and amorphous forms.2. Accumulation in the layer above the capillary water zone as a result of evaporation of ground water in arid areas. 3. Windblown secondary gypsum forms the gypseous desert area and deposited on other soils, or precipitated from irrigation water.The main character in dry condition was the bearing capacity of each test under a general shear failure at static and cyclic loading [4] for three types of soils, natural gypseous, natural gypsified and artificial gypsified soils.For the previous studies, some researchers study the gypseous soils with different methods using devices for tests, at dry condition under static or cyclic loads on natural gypseous soil models, but a little deals with gypsified and artificial soil models, some of these studies were shown in this study as follows:Al-Qaissy, investigate gypsum migration process resulting a gypsum concentration with different gypsum content in soils, and its effect on compressibility and shear strength. Simulation of the natural field conditions were furnished to these samples in the laboratory. The testing program was conducted at different ages of 0, 1, 3, and 6 months in order to study time effect. The test results reveal that, migration process of gypsum took place in thesimulated gypsified samples, causing leaching of gypsum in certain zones. The soil exhibited lower compressibility and higher collapsibility characteristics as the gypsum content increased under leaching process, time progression and gypsum precipitation

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