Influence of Physicochemical Interactions on the Mechanical Behavior of Tropical Residual Gneiss Soils

M.M. Futai, W.A. Lacerda, A.P.S. Martins

Article

Soils and Rocks, São Paulo, 38(1): 9-25, January-April, 2015 | PDF


Abstract

When soils are inundated with liquids other than water, a physicochemical interaction takes place and can alter the soil behavior. Depending on the type of soil and on the solution, the soil can become more compressible and lose strength (or the contrary). In this paper, tropical residual gneiss soils are used, namely lateritic and saprolitic soils. The solution used are a mixture of sodium hexametaphosphate and sodium carbonate. Solutions were prepared with different concentrations such that the pH value remained at 10.5. Sodium concentration was used to interpret the results. Oedometer and triaxial compression tests were carried out with samples permeated with these solutions. The lateritic soil behavior was found to be quite distinct from the saprolitic one. While the lateritic soil becomes much more compressible upon the increase in the concentration of sodium, the saprolitic soil swells progressively. However, the compression curve converges at more elevated stress levels. The stress-strain curve also alters in relation to the concentration. The lateritic soil loses strength and its stiffness is greatly reduced with the increase in concentration.


Submitted on August 7, 2013; Final Acceptance on March 26, 2015; Discussion open until December 31, 2015.