Effect of sand column on compressibility and shear strength of fibrous peat

Peat is found in many countries throughout the world where it can be generally seen in thick layers in limited areas. Peat is an extreme form of soft soil and is considered problematic due to the low shear strength and large compressibility. This project presents laboratory finding on the compressibility and shear strength characteristics of fibrous peat with sand column.The peat used in the study is taken from Sakarya region, Turkey. It is classified as fibrous peataccording to ASTM D 1997-91 and due to its low to medium degree of decomposition classified as H_1-H_4 in von Post scale. The natural water content of the peat is 236 % and its liquid limit is 119%. In all tests, the fibrous peat used for the test passing #200 and remain on #100. The rounded sand used for making sand column is poorly graded passing from 2 mm sieve size and retaining on 0.075 mm sieve size. The tests focused on effect of diameter of granular column on shear strength and compressibility of the organic soil.Four different sand column diameters were used for compressibility and shear strength testswere (1.7, 2.5, 3.5and 4.7cm).All tests results showed that; when the ratio of sand column surface to organic soil surface area (S/O) increases; compression index (c_c); recompression index (c_( r)); and volume compressibility (m_v) decreases. Also,sand columns causes increase in (IFA)and reduction in (C) of the organic soil.