ORIGINAL PAPER Numerical Analysis of Multi Layer Geosynthetic-Reinforced Granular Bed over Soft Fill Kousik Deb Æ N. Sivakugan Æ Sarvesh Chandra Æ P. K. Basudhar Received: 6 September 2006 / Accepted: 5 July 2007 / Published online: 25 July 2007 Ó Springer Science+Business Media B.V. 2007 Abstract In this paper, considering the plain strain conditions, a numerical study has been conducted to investigate the behavior of multi layer geosynthetic- reinforced granular bed overlying a soft soil using the Fast Lagrangian Analysis of Continua (FLAC) pro- gram. The granular fill, soft soil, and geosynthetic reinforcements are considered as linear elastic mate- rials. The geosynthetic reinforcements are modeled as cable elements fully bonded with the surrounding soil, thus neglecting any slip. The results obtained from the present investigation showed very close agreement when compared with the results of finite element analysis and lumped parameter modeling. The distri- bution of vertical, lateral and shear stresses in the soil are greatly affected as the number of reinforcement layers is increased. If the tensile stiffness of geosyn- thetic layers increases and its value is no more than 4,000–5,000 kN/m, the settlement of the reinforced foundation decreases significantly. The reduction in settlement is insignificant when the tensile strength of the geosynthetics exceed the above value. Keywords Geosynthetic reinforcements  Granular bed  FLAC  Multi layer  Soft soil Notations B Half width of uniform surcharge load (m) E s Elastic modulus of soft soil (N/m 2 ) E gb Elastic modulus of granular fill (N/m 2 ) E g Elastic modulus of geosynthetic layer (N/m 2 ) H s Thickness of the soft soil (m) J Axial stiffness of the geosynthetic layer (N/m) k s Modulus of subgrade reaction of the soft soil (kN/m 3 ) L Half width of geosynthetic-reinforced zone (m) q Footing pressure on the top granular layer (N/m 2 ) t Thickness of the geosynthetic layer (m) w Vertical settlement (m) W Nondimensional vertical settlement (w/B) (dimensionless) x Distance from the center of loading (m) X Nondimensional distance (x/B) (dimensionless) Present Address: K. Deb (&) Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee 247667, India e-mail: kousik_deb@rediffmail.com K. Deb  S. Chandra  P. K. Basudhar Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India K. Deb e-mail: kousik_deb@rediffmail.com S. Chandra e-mail: sarv@iitk.ac.in P. K. Basudhar e-mail: pkbd@iitk.ac.in N. Sivakugan Civil & Environmental Engineering Department, James Cook University, Townsville, QLD 4811, Australia e-mail: siva.sivakugan@jcu.edu.au 123 Geotech Geol Eng (2007) 25:639–646 DOI 10.1007/s10706-007-9136-5