There are many treatments for such soils, some of them are physical like earth reinforcement, compaction. The solubility depends on temperature degree, atmospheric pressure, PH of the dissolved liquid. Gypsum salts is one of highly dissolved salts in water. The presence of gypsum in some regions reaches up to 70%. One of the effected problems is the presence of gypseous soil. The engineering problems faces civil engineer in building and construction, is almost foundation problems results from the properties of the beneath soil. The results of laboratory model tests shows that the settlements results from specimens soaked with lubricating oil, Gasoil and Kerosene, are much less than the settlements that belong to soaking with water (reduce settlement to about one third) and considered high improvement of such problematic soil by wetting with oil derivatives. One sample was wetted with water for comparison the settlement was recorded with soaking time at a constant stress level. Three oil derivatives (Kerosene, Gasoil and crude oil) were used for laboratory model tests by wetting Calcareous soil with it. Fix stress system was used which applies 50 kN/m2, the loading frame was manufactured in a way that keeping the weights over footing stable without tilting. A laboratory model included soil with 70% and 50% CaCO3 compacted to 11 kN/m3. This study shines the lights about the behavior of Calcareous soil subjected to three oil derivatives (kerosene oil, crude oil, gas oil and a sample wetted with water to make good comparison ,and study effect of addition of this products on the collapsibility. Oil tanks or pipes may damage from any reason, and the oil products may leak from these structures to the soil and infiltrate through soil skeleton and may cause leaching to CaCO3 salt particles in some regions in Iraq, as example the Baiji Oil Station or Al-Mosel Dam, CaCO3 percent reaches more than 40%.
It is very dangerous for structures when constructing on such soil especially when high stresses are applied on it. Calcareous soil is stiff and very hard if it is in a dry phase it becomes collapsible and very week when wetted with water. The dissolution of salts increases with temperature, atmospheric pressure, in addition to the acidity of the dissolves solution. Keywords: Sabkha Soil, Collapsible, Chemical Additives, Treatment, Improvement.Ĭalcareous or salty soils are the soils which are containing highly dissolved sodium or calcium salts in natural conditions. The collapse potential (S/B%)* reduced 50%, when increasing compaction of sabkha soil model from 17.7 to 19 kN/m3. This study also, shines the light on the effect of compaction on the properties of sabkha soil. While mixing sabkha soil with 3% lime will reduce collapse settlement 47%, On the other hand, mixing sabkha soil with 1% cement slurry increase the collapsibility 3%. Mixing sabkha soil with 5% of cement will reduce collapse potential (S/B%)* upon wetting, 97%. The study includes also the effect cement and lime addition with different percentages(1%, 3% and 5%), on the collapsibility of sabkha soil. Dial gages is attached to the fix table and place on the footing, to record settlement with time. The footing used is 75mm diameter circular steel plate and 20mm thickness and hold fix stress, with the aid of loading frame which in turn is attached to a firm table.
The sabkha soil is prepared by mixing ordinary soil with specified quantities of sodium chloride salt to have different percentages of salinity. A laboratory model, manufactured locally was used for this study. The primary objective for this study is to investigate the behavior of single footing over different percentages of sabkha soil (5%, 10%, 20%, and 40%). The presence of salts in soil may cause severe problems to structures constructed on it, because of high dissolution of salt particles when subjected to water from any source.
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