ORIGINAL PAPER Axi-symmetric Analysis of Geosynthetic-reinforced Granular Fill-soft Soil System with Group of Stone Columns Kousik Deb • P. K. Basudhar • S. Chandra Received: 30 July 2008 / Accepted: 10 December 2009 / Published online: 25 December 2009 Ó Springer Science+Business Media B.V. 2009 Abstract The paper presents a mechanical model to predict the behavior of geosynthetic-reinforced gran- ular fill resting over soft soil improved with group of stone columns subjected to circular or axi-symmetric loading. The saturated soft soil has been idealized by spring-dashpot system. Pasternak shear layer and rough elastic membrane represent the granular fill and geosynthetic reinforcement layer, respectively. The stone columns are idealized by stiffer springs. The nonlinear behavior of granular fill and soft soil is considered. Consolidation of the soft soil due to inclusion of stone columns has also been included in the model. The results obtained by using the present model when compared with the reported results obtained from laboratory model tests shows very good agreement. The effectiveness of geosynthetic reinforcement to reduce the maximum and differen- tial settlement and transfer the stress from soft soil to stone columns is highlighted. It is observed that the reduction of settlement and stress transfer process are greatly influenced by stiffness and spacing of the stone columns. It has been further observed that for both geosynthetic-reinforced and unreinforced cases, the maximum settlement does not change if the ratio between spacing and diameter of stone columns is greater than 4. Keywords Axi-symmetric loading  Geosynthetic reinforcement  Group of stone columns  Settlement  Soft soil List of Symbols a Radius of circular loading b Radius of geosynthetic-reinforced zone d c Diameter of the stone column E c Elastic modulus of the stone column material E s Elastic modulus of the soft soil G b0 Initial shear modulus of the bottom granular fill layer G  b0 Normalized G b0 G t0 Initial shear modulus of the top granular fill layer G  t0 Normalized G 0t H b Thickness of the bottom granular fill layer H t Thickness of the top granular fill layer K. Deb (&) Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India e-mail: kousik_deb@rediffmail.com P. K. Basudhar Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: pkbd@iitk.ac.in S. Chandra School of Civil Engineering, Surveying and Construction, University of Kwazulu-Natal, Howard College Campus, Durban, South Africa e-mail: Chandra@ukzn.ac.za; sarv@iitk.ac.in 123 Geotech Geol Eng (2010) 28:177–186 DOI 10.1007/s10706-009-9291-y