Volume changes of a collapsible soil selected from Hawy Al-Kanissa in
Mosul city were studied. The Influence of addition of (5, 15 and 30) % of low (CL)
and highly plastic (CH) clayey soil were studied. Many variables as: the initial dry
unit weight, water content and applied stresses on volume change were considered.
State diagrams representing gradual volume change due to these variables were also
presented and discussed.
The main results were showed that the collapse potential (Cp) increased
continuously for samples mixed with (CL) soil while there were a maximum value at
(5%) of (CH) soil. At low unit weight, (Cp) for samples mixed with (CL) reached a
highest value at certain stress, then started to decrease, while it increased
continuously using (CH). (Cp) of soils containing (CH) was found to be less than that
mixed with (CL) soil. Concerning soil volumetric changes using state diagrams
presentation, volume change for undisturbed natural soil at low moisture content was
found less than that in disturbed samples, but the inverse was obtained at saturation.
Besides that, volume changes increased with the increase of the clay additive in
different manner for (CL) and (CH) soils.
Keywords: Clay, Collapsible soil, Volume change, unsaturated soil.