BEHAVIOUR OF FOOTINGS RESTING ON REINFORCED FLYASH

Abstract

Compacted Flyash has been satisfactorily used in embankments, road sub-bases and also for structural fills but the main limitation of such embankment is that of their limited load carrying capacity and poor settlement characteristics. The performance of such materials can substantially be improved by introducing reinforcement elements in the direction of tensile strain in the way as in reinforced concrete. The present dissertation deals with the behaviour of footings resting on reinforced flyash. The objective of the dissertation is to study the effect of a single layer of geogrid reinforcing material on the improvement of bearing capacity and settlement characteristics of square footing. A square footing of size 100 mm2 in a tank size lm x lm x 1m have been used for the model test and is tested on flyash at Optimum moisture content and submerged condition in case of un-reinforced flyash and reinforced flyash. As flyash is a material of low bearing capacity it is necessary to reinforce it. Geogrid has been used to reinforce the flyash. The size of the reinforcement is kept as 1B, 1.5B, 2B, 2.5B and 3B (Where B be the width of footing). The Geogrid is placed below the footing at 0.25 times the size of footing. A specially designed loading device is used for the application of eccentric-oblique loads. The load on the footing is applied at the eccentricities of 0, 0.1, and 0.2 and the inclination with vertical is kept as 0°, 10°, 20°. The pressure-settlement, pressure-tilt and pressure-horizontal displacement curves has been plotted for different load combinations and the ultimate bearing capacity, settlement and tilt are obtained for both un-reinforced and reinforced flyash. Further, from this data the non-dimensional charts are developed to evaluate the ultimate bearing capacity, settlement and tilt of footings.