Abstract

The aim of this work is to study the effect of organic matter content on the
Engineering properties of expansive clayey soils. Soil from the district of
Qadisiyah the second ,in Mosul have been used. Its engineering properties were
indicated. For the resemblance to the organic soils, dry leaves of the wide spread
trees all over Iraq (Youkaliptous) was used.
The crushed dry leaves, passing sieves No.40 were mixed with the soil, with
the amount (5, 10, and 15) % from dry weight of soil, then, samples engineering
properties were indicated. The study concluded that the presence of organic
matters can cause instability in soil properties generally, so that its decrease the
plasticity(more than 35%), shrinkage(25% decreasing at 15% organic content)well
as 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 the
optimum moisture content(25%) with decrease of the dry unit weight.