EFFICACY OF SODIUM CARBONATE AND CALCIUM CARBONATE IN STABILIZING A BLACK COTTON SOIL
The problem of damage to structures in expansive soils is world wide. These soils are very often referred as black cotton soils. The properties of black cotton soil may be improved to make the soil suitable for construction purposes. There are several techniques to improve the soil properties like sand cushions, CNS layer techniques, sand columns, stone columns, vibration techniques and by adding chemicals etc. Among these, chemical stabilizing is more expensive than other types of stabilization methods. But the main advantage of it is that setting time and curing time can be controlled. The efficacy of sodium carbonate and calcium carbonate is stabilizing a black cotton soil is presented in this paper. The efficacy of calcium carbonate is much better than sodium carbonate from strength and stability point of view.
Evaluation of the swelling pressure for expansive soils
The interaction between light structures and expansive soils as mainly active clays was studied since the 1950’s. The first stage in foundation design on this problematic soil is the evaluation of the swelling potential, based on which one identifies the clay’s activity and its correlation with the value of the swelling pressure (ps) for the decisional support of the geotechnical design (p effective > ps). In the literature there are many formulas that can be used to predict the swelling pressure based on the correlation between various geotechnical parameters. This paper provides the swelling pressure as correlation with the consistency index (CI) and the liquid limit (LL), by linear regression of the experimental results for the 56 active clays from seven countries. Using the analytical methods, one can predict the total heave of a floor slab founded on expansive clay. The validity of the proposed correlation has been tested in the prediction of the total heave in the centre of a floor slab for a light industrial building in North-Central Regina, Saskatchewan, Canada.
Significance of amorphous material relative to sensitivity in some Champlain clays: Discussion
In considering the significance of amorphous materials to the sensitivity of Canadian clays the authors have made an informative contribution to the sensitive-clay literature. The authors have established a comprehensive framework for analysis that other researchers would do well to follow in subsequent studies. In the writer's opinion these analyses should be considered in the light of all research into amorphous materials and a brief review of Norwegian work would be appropriate. The Norwegians led sensitive-clay research into the 1960's and some aspects of this work, augmented by work recently performed by the writer, are relevant to the paper under discussion. The presence of amorphous compounds in sensitive clays has been recognized by several Norwegian workers (Moum 1967; Bjerrum et al. 1969; Lerken 1970). The amorphous matter appears to be insoluble-iron and aluminium compounds, which are liberated from mineral phases by in situ weathering. Other soluble cations, notably K+, Ca2+, and Mg2+ also are liberated by mineral disintegration; these do not form amorphous precipitates but they can have an important electrochemical influence on the clay. It is evident from laboratory observations that mineral disintegration becomes active when the leaching process introduces fresh waters, which result in a change of pH and oxidation capacity (Bjerrum 1967; Moum 1967). The interaction of these released cations with the clay system has been summarized by Lerken (1970); the cations may be leached out with the remaining salts in the pore water, enter adsorbed positions by displacing more weakly adsorbed cations, or precipitate as insoluble amorphous compounds. From work concerning chemical additions to quick clays Lerken (1970) concluded that there is a fundamental differ-