Numerical Analyses on Cellular Mattress–Reinforced Fly Ash Beds Overlying Soft Clay

Abstract

This paper presents the results of large-scale numerical modeling of cellular mattress–reinforced fly ash beds overlying soft clay using a finite-element program. The cellular mattress was a honeycomb structure consisting of interconnected multiple circular cells. The influence of the height, diameter, and tensile stiffness of the cell and the width of the entire mattress on the pressure-settlement response of footing, surface deformation during footing settlement, and mobilization of hoop tension in the cell walls are illustrated. Results from the numerical analyses indicate an improvement in footing capacity of approximately1.4 times greater over fly ash bed by inclusion of a single geotextile separator representing jute geotextile in between the fly ash bed and underlying clay. The cellular mattress–fly ash composite bed produced an approximately sevenfold increment in the footing capacity compared with the unreinforced fly ash bed both in presence of the jute separator. The mattress-reinforced beds produced better footing capacity with an increase in the height and width of the mattress and the tensile stiffness of the cell wall. It is satisfactory to acquire the optimization for the height and width of mattress and the tensile stiffness of the cell wall. For a particular mattress width and height, the footing capacity increased with a reduction in the cell diameter. The cell at the mattress center mobilized maximum hoop tension that was lesser in the cells successively toward the mattress periphery. Also, more hoop tension was mobilized with an increase in the tensile stiffness of cell wall. Small-scale finite-element models were created using the same material models and properties as those used for the large-scale modeling to validate the program with laboratory small-scale model tests comprising the same model conditions. The finite-element results were found to be in good agreement with the experimental results.