ACEE – Volume 02(3), 162-171 Advances in Civil and Environmental Engineering www.jacee.us - copyright © 2013 Jacee.us official website. ENGINEERING PROPERTIES OF STABILIZED SOIL OF GISOOM FOREST AREA USING CEMENT-SAND MIXTURE Mohammad Nikookar 1* , Mehdi Karimi Pashaki 1 , Mahyar Arabani 2 1 M . Sc., Department of Civil Engineering, University of Guilan, Rasht, I. R. Iran. 2 Professor, Department of Civil Engineering, University of Guilan, Rasht, I. R. Iran. * Corresponding author, E-mail: nikookar2006@yahoo.com Abstract Forest Organic Soils are deposits which are extremely soft, wet, and unconsolidated. High compressibility (or high settlement) and low shear strength of such soils can contribute to some geo- technical problems. This encounters construction on organic soils to have high geo-technical risks and costs. Chemical admixture (chemical stabilization) is one of the methods of stabilization that treats the soil by adding some kind of chemical compound for triggering a chemical reaction. In this regard, Cement- which is a sand mixture- is used to improve the bearing capacity and low compactibility of soils. This paper tends to describe the geotechnical characteristics of the cement extracted from Forest Organic Soils of the Northern areas of Iran. This study makes use of Atterberg Limits, Compaction Test, Unconfined Compressive Strength, and CBR Tests for sand mixtures (including cement-treated and untreated soils). The results indicated that an increase in the cement can contribute to the improvement of the geotechnical characteristics of the soils. Keywords: Forest Organic Soil, Cement, Sand, CBR, Unconfined Compressive Strength, Compactability, Atterberg Limits 1. Introduction Based on the definition by ASTM D4427-92 (1997), organic soil is a naturally-occurring and highly organic substance which is primarily derived from plant materials. To be mentioned generally, all soils with higher than 20% organic content are in the category of organic soils. Peat soils are a subcategory of organic soils with more than 75% organic content (Huat, 2004). Compared with other organic soils, Peat soils have lower ash content ( i.e., less than 25% by dry weight) and compared with Phytogenic ISSN 2345-2722