RELIABILITY BASED ANALYSIS OF BEARING CAPACITY OF FOOTINGS ON SOFT SOIL STRENGTHENED BY STONE COLUMNS

Uncertainties in geotechnical engineering are inevitable. The soil properties may disperse within a significant range over a domain. Thus, the factor of safety is used in the deterministic approach which account for the uncertainty associated with the soil properties. Deterministic approach does not consider the sources and amount of uncertainty associated with the system. Limit state design of the structure is difficult to estimate using deterministic methods. So, it is reasonable to study the probability of failure of the structure. In this study, a procedure for carrying out reliability analysis of bearing capacity of foundation resting on soil improved by stone columns is described. The procedure requires definition of standard deviation of the undrained shear strength, shear strength of the stone and the surrounding soil. The procedure is an extension of the point estimate method in which the expected values of the standard deviation of the capacity and demand functions are calculated. The probability of failure, the reliability, central factor of safety and reliability index are calculated as appropriate. Two non-linear regression models have been made using SPSS V.20 (Statistic Computer Application) program. Data of experimental work from previous studies are analyzed for building a bearing capacity equation of floating and end bearing stone column group.