Stabilization of Organic Soils Using Lime

Organic soil is one of the important problematic soils in construction industry. The effect of organic materials on engineering features of soils is variable depending on the type and content of organic matter. The main purpose of this study is to investigate the effects of organic matter on the strength and physical properties of organic soils and its improvement. One of common improvement methods in this type of soils is chemical stabilization with lime, cement, etc. For this purpose, organic matter (peat) was added to inorganic clayey soil at three levels (3%, 6%, 9% by weight). The physical properties of the mixtures were determined by conducting a series of laboratory tests including Atterberg limits, compaction, unconfined compressive strength, and swell characteristics tests. The results showed that with increasing organic matter content, the percentage of lime required to modify the soil, changed too dramatically. Also results indicate that by increasing three percent in organic matter, the amount of required lime increases by two percent. The study of plasticity and swelling in each three soil types shows that these parameters are decreased after stabilization, but with increasing amount of organic matter, the rate of reduction can be reduced. To evaluate the mechanical properties of these soils, unconfined compression strength (UCS) test was carried out on lime treated samples. The results show that in all samples after 28 days of curing, the UCS has been increased noticeably. This growth in strength decreases with increasing organic matter content. pH of all samples has been reduced after 28 days of curing and the amount of reduction has been increased with higher organic matter. Considering the results, with increasing organic matter content from 0 to 9%, only soil with organic matter of 3% suitably stabilized.