CHARACTERSTICS OF GYPSEOUS SOILS TREATED WITH CALCIUM CHLORIDE SOLUTION

Abstract

الخلاصةAbstract Gypseous Soils are distributed in many regions in the world including Iraq, which cover about (31.7%) of the surface area of the country. Existence of these soils in the west part of Iraq, some time with high gypsum content, caused difficult problems to the building and strategic projects due to dissolution and leaching of the gypsum slates by the action of water flow through soil mass. In this study, compressibility and shear strength characteristics are studied for three gypseous soils brought up from Al-Khalidiah, Heet and Al-Ramadi areas with gypsum content (38, 53 and 72%) respectively. The results of the tests are indicated that these soils consider as high collapsible soils. The shear strength parameters (c and 􏰀) are decreased upon soaking in water. The main reduction is in cohesion intercept (c), whereas there is a slight reduction in (􏰀) value. The effect of treatment with Dihydrate Calcium Chloride (CaCl2.2H2O) as water solution on compaction, compressibility, leaching, permeability and shear strength characteristics of Heet soil is also investigated. It is found that the maximum dry unit weight increase and optimum moisture content decrease with increase the concentration of calcium chloride in the molding water. It is concluded that the engineering properties of the samples are highly improved when the samples are soaked in calcium chloride solution at (20%) concentration. Where, considerable reduction is observed in compressibility, collapsibility, coefficient of permeability, percentage of dissolved gypsum and leaching strain. Also, the treatment minimizes the reduction in cohesion component (c) upon soaking in water and slightly decrease the angle of internal friction (􏰀). Analysis of the tests results are showed that the using of calcium chloride as solution in improvement the gypseous soil is more efficient than using it as powder.