Reza Babaie - M.Sc. of Geotechnical Engineering, Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Rouzbeh Dabiri - Assistant Professor, Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran

Liquefaction in sand and silty soil layers due to earthquake is one of the important phenomenon in earthquake geotechnical engineering. During the earthquake pore water pressure increases in saturate soil layer until equal to total stress. Then, effective stress decreases and equal to zero. In this condition soil layer loses shear strength and bearing capacity. The results of this phenomenon happens in soil layers are instability, wide settlement in ground level and underground. Main idea in this research is improvement of liquefiable soil with using stone columns. So that, diameters of stone column is 0.6, 1.2 and 1.8 meters and length equal to 9 meters were considered. Also, distance of between stone columns equal to 0.6, 1.2 and 1.8 meters assumed. Overburden amount due to building weight effective on soil layers equal to 5 and 15 stories were selected. FLAC 2D program used for dynamic analysis and analyses results in liquefiable soil layers were evaluated in 1.5, 4.5 and 6 meters depths. Results of this study showed that in terms of rate of exceed pore water pressure, in 60 cm distance between stone columns and both 5 and 15 story building (Overburden), in all of diameters liquefaction happens in soil layers. While, distance between stone columns increased 60 to 120 cm, drainage system in saturate soil layers worked properly and in deep down liquefaction no observed. Although, stone columns with 1.2 meters diameters and distance value 1.2 meters between each other’s in two overburden have suitable performance in soil layers improvement against liquefaction. So that, rate of exceed pore water pressure during dynamic loading decreased and settlement values declined too. One of the important issues in liquefaction is vertical settlements. Based on data analyses, it was observed with increasing diameter of stone columns and decreasing interval between them settlement due to liquefaction in saturate soil layers is reduced.

Liquefaction, Stone column, Soil Improvement, Settlement, FlAC 2D