Investigation of the Impact of Unsaturated Conditions on Mechanical Properties of Stabilized Soils with Hydrated Lime

Changes in surface and subsurface moisture content is one of the devastating factors affecting on evaluating performance of soil behavior such as erosion, swelling, shrinkage, differential settlement, freeze and thaw cycles, liquefaction phenomena, landslides and environmental contamination. In the present laboratory research, stabilization of two artificial soil samples with different combinations of sand and low plasticity clay, with 3, 5 and 7 percent of hydrated lime, was investigated and compressive strength of the stabilized specimens after a curing period of 28 days, on the basis of standard proctor compaction, under saturated, unsaturated and dry conditions have been estimated by unconfined compressive strength tests. The filter-paper method, as a measure of equilibrium moisture content and solution of computing the suction, has been selected for estimation of inherent characteristics of soil suction in the presence and absence of lime addition in the unsaturated condition. Also, hydraulic conductivity of the stabilized and cured specimens for 7 and 28 days was measured. Results of the tests during a drying cycle hysteresis, demonstrated that matric suction of clay soil samples was about 11 times of sandy soil samples, and the lime content intensified pore water retention and estimation of soil suction. The stabilized clay and sandy soil samples lost their average unconfined compressive strength by 87 and 83 percent, respectively, because the lime adhesiveness became unstable in the presence of water. Despite the expected results, factors such as heterogeneity in the fabric of soil aggregates during stabilization, weakness of lime adhesion and changes in the gradation situation from fine-grained to coarse-grained particles during the addition of lime, led to permeability increase over the 7- and 28-day curing period.