Flexural response of surface strip footings resting on reinforced viscoelastic foundation beds

A generalized method of analysis has been proposed to determine the flexural response of a surface strip footing resting on a compacted granular foundation bed overlying a clay layer of soft to medium consistency with geogrid/geomat/geocell reinforcement at their interface. The footing and the reinforcement are idealized as beams with sufficient flexural rigidity. The compacted granular bed and the clay layer are idealized by Winkler springs and four-element standard viscoelastic Burger element respectively. The rationality of choosing Burger model to represent the time-dependent behavior of compressible viscoelastic medium has been elucidated. A non-uniform variation of the subgrade modulus is assumed along the width of the footing at the soil-structure interface. Governing differential equations, predicting the response of the reinforced foundation bed under the given loading condition, are developed; and solved using the Finite Difference Method (FDM). Based on the convergence study, optimal size of mesh segment is determined; and the correctness of the study has been established by comparing the solution from a degenerated case with the standard solutions available in literatures. Effect of variation in the viscoelastic parameters of the Burger model on the flexural response of the reinforced foundation bed has been discussed. It is shown that the Burger model can be degenerated to any lower order models by proper modifications in the viscoelastic parameters of the Burger model. Significant variation in the bending moment of footing is observed with elapsed time, thus revealing the necessity of considering the effect of time in the design of reinforced viscoelastic foundation beds.