The Effect of Organic Matter’s Content on the Engineering Properties of Expansive Soils

Abstract

The aim of this work is to study the effect of organic matter content on theEngineering properties of expansive clayey soils. Soil from the district ofQadisiyah the second ,in Mosul have been used. Its engineering properties wereindicated. For the resemblance to the organic soils, dry leaves of the wide spreadtrees all over Iraq (Youkaliptous) was used.The crushed dry leaves, passing sieves No.40 were mixed with the soil, withthe amount (5, 10, and 15) % from dry weight of soil, then, samples engineeringproperties were indicated. The study concluded that the presence of organicmatters can cause instability in soil properties generally, so that its decrease theplasticity(more than 35%), shrinkage(25% decreasing at 15% organic content)wellas high compressibility due to gaining low strength. It has been observed, as well,that high organic matters cause decrease in shear strength(more than 50%decreasing in cohesion at 15% organic content) and considerably increase in theoptimum moisture content(25%) with decrease of the dry unit weight.