Flexural response of footing on reinforced granular beds of variable subgrade modulus

Abstract

The paper pertains to the study of the flexural response of a shallow footing resting on a compacted granular bed overlying a deposit of poor granular soil, with reinforcement (e.g. geogrid and geocells) placed at the interface of the two media. The footing and reinforcement are considered as free ended beams. The granular soil media are represented by a series of Winkler springs. Taking into account the effect of confining pressure along the footing and reinforcement at the beam-soil interface, various distribution of subgrade modulus along the length of footing and reinforcement (uniform, linear and quadratic) are considered. Governing equations for the above problem are derived and subsequently normalized, which is then solved by using Finite Difference Method (FDM) in conjunction with Gauss-Seidel Iterative Technique (GSIT). Comparison of the obtained solutions with those available in literature for the case of uniform subgrade modulus exhibited a deviation of 24%-40% in the settlement characteristics of the reinforced foundation bed. Parametric studies were performed to study the effect of various parameters, such as, relative flexural rigidity of beams (<i>R</i>), relative length of beams (<i>l_n</i>), relative stiffness of soils (<i>k_r</i>), relative depth of placement of reinforcement (H'), effect of interface friction and effect of variation in subgrade modulus. The developed method has been found to be realistic in predicting the behavior of reinforced foundation beds.