Collapsible soils are known as problematic soils, which possess considerable strength when dry and lose their strength when inundated experiencing excessive settlements. The soil response to inundation (i.e. landslides or significant soil settlements) could not be predicted beforehand. The irrecoverable volume reduction of collapsible soils takes place fast and sudden and no measurements can be taken to stop the problem once it initiates. The collapse potential increases with time due to soaking and leaching which is attributed to the dissolution and washing out of gypsum.In this paper, a comparison is made between the collapse potential predicted form laboratory standard collapse test with filed collapse (coefficient of resolving slump) estimated from plate loading test. The soil site for investigation was in Rumaila, Basrah Governorate. Results of collapse test carried out on two samples showed that the collapse potential, Ic of the two samples is 5.091% and 3.502%, the soil is considered of moderate degree of collapse. The coefficient of average resolving slump for saline soil was calculated from field plate load test to be 0.94% to 1.2%. The difference in boundary conditions between the two approaches was found clear in the evaluation of collapse potential.

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For construction of structures on soft clay layers, engineers must have to consider the consolidation behaviours of such soil. Due to the viscosity of clayey soils, their organic content strongly influences on consolidation behaviours as well effecting on vertical stress. Laboratory studies on soft soil have offered better understanding and thus better prognosis of these behaviour, and several related tests are performed and presented in this research. Two odometer tests were done, the first being a conventional odometer test for three soil types to find their compressibility parameters, while the second consisted of a series of long term odometer tests to find the creep coefficient for each type of soil. Seven incremental consolidation pressures were applied to each soil sample with different organic content (25 kPa, 50 kPa, 100 kPa, 200 kPa, 400 kPa, 800 kPa and 1600 kPa). A detailed study of the results obtained from this incremental loading was then undertaken. From the consolidation test, the values of different parameters such as the compression index (Cc) and secondary compression index (Cα) were obtained, and it was found that Cc and Cα values increased with increased organic content in the soil. The study also found that, generally, Cα decreases with incremental loading.

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