Reliability Based Performance Evaluation of Stone Column Improved Soft Ground
The present study considers the effect of variation of different geotechnical random variables in the design of stone column-foundation systems for assessing the bearing capacity and consolidation settlement of highly compressible soil. The soil and stone column properties, spacing, diameter and arrangement of stone columns are considered as the random variables. Probability of failure (Pf) is computed for a target degree of consolidation and a target safe load by Monte Carlo Simulation (MCS). The study shows that the variation in coefficient of radial consolidation (cr) and cohesion of soil (cs) are two most important factors influencing Pf. If the coefficient of variation (COV) of cr exceeds 20%, Pf exceeds 0.001, which is unsafe following the guidelines of US Army Corps of Engineers. The bearing capacity also exceeds its safe value for COV of cs > 30%. It is also observed that as the spacing between the stone column increases, the probability of reaching a target degree of consolidation decreases. Accordingly, design guidelines, considering both consolidation and bearing capacity of improved ground, are proposed for different spacing and diameter of stone columns and geotechnical random variables.
 D.A. Greenwood, “Mechanical Improvement of soils below ground surface.” Conf. on Ground Engg, Institution of Civil Engineers, London, 1970, pp.11-22.
 A.P. Ambily and S.R. Gandhi, “Behavior of stone columns based on experimental and FEM analysis.” J. Geotech. Geoenviron. Eng., ASCE, Vol. 133, No. 4, 2007, pp. 405-415.
 K. Deb and S. Shiyamalaa, “Effect of Clogging on Rate of Consolidation of Stone Column–Improved Ground by Considering Particle Migration.” Int. J. Geomech., 10.1061/(ASCE)GM.1943-5622.0000492, 2015, 04015017.
 J. Alonso and R. Jimenez, “Reliability analysis of stone columns for ground improvement.” GeoRisk, ASCE, 2011, pp. 493-500.
 S.C. Douglas and V.R. Schaefer, “Reliability of the Priebe method for estimating stiffness.” Ground Improvement, Vol. 167 (G12), 2012, pp. 108-121.
 M.W. Bari and M.A. Shahin, “Probabilistic design of ground improvement by vertical drains for soil of spatially variable coefficient of consolidation.” Geotext. Geomem., Vol. 42, No. 10, 2014, pp. 1-14.
 K. Deb and A. Majee, “Probability-based design charts for stone column-improved ground.” Geomechanics and Engineering, Vol. 7, No. 5, 2014, pp. 539-552.
 A. Choobbasti, A. Zahmatkesh and R. Noorzad, “Performance of Stone Columns in Soft Clay: Numerical Evaluation.” International Journal of Geotechnical and Geological Engineering, Vol. 29, No. 5, 2011, pp. 675 – 684.
 J.S Lee and G.N Pande, “Analysis of stone-column reinforced foundations.” International Journal for Numerical and Analytical Methods in Geomechanics, Vol. 22, No. 12, 1998, pp. 1001-1020.
 IS 15284 (Part 1). “Design and Construction for Ground Improvement – Guidelines: part 1 stone column”, 2003.
 Han J. and Ye S.L., “A Theoretical Solution for Consolidation rates of Stone Column-Reinforced Foundations Accounting for Smear and well-resistance effects”, The International Journal of Geomechanics, Vol. 2 No. 2, pp. 135-151, 2002.
 J.K. Mitchell, “Soil improvement – State of the art report.” Proceedings of the 10th ICSMFE, Stockholm, The Netherlands, June, 4, 1981, pp. 509-565.
 J.M. Duncan, “Factors of Safety and Reliability in Geotechnical Engineering.” J. Geotech. Geoenviron.Eng., ASCE, Vol. 126, No. 4, 2000, pp. 307-316.
 G.B. Baecher and J.T. Christian, “Reliability and Statistics in Geotechnical Engineering.” Wiley, New York, 2003.
 M.R. Madhav and P.P. Vitkar, “Strip footing on weak clay stabilised with granular trench or piles.” Can. Geotech. Jrnl., Vol. 15, No. 4, 1978, pp.605-609.
 J.E. Bowles, “Foundation Analysis and Design.” McGraw Hill Higher Edn, 5th edn, 2001.