BEHAVIOUR OF FOOTINGS ON TWO LAYERED REINFORCED FLYASH

Abstract

The growth in population and industrial development in any developing country needs a sustained supply of electrical energy. Major source of this electrical energy, in India as well as in the entire world, is the thermal power, which constitutes 70 % of the total energy production, which is responsible for the production of enormous quantity of ash, as a by-product, due to combustion of the pulverized coal. In these thermal power stations, the burning of coal at high temperatures produces coal ash as a waste material. The huge quantity of ash being accumulated over the years is like to pose a colossal problem for its disposal and cause environmental pollution leading to health hazards. Fly ash is a versatile material with many applications in the construction industry. However, only about 20 % fly ash produced in the world is utilized in variety of applications and the balance is dumped as a waste material. The main reason is probably the distance, as most of the power plants are located far away from the urban population and the transportation costs overcome the beneficial applications. The fly ash can be used in the manufacture of pozzolona cement, quality concrete, bricks, cellular building block, construction of structural fills, embankments and dams etc. The current excerise is to study the behaviour of eccentrically and obliquely loaded footings on two layered reinforced fly ash and to develop the non dimensional charts to evaluate the bearing capacity, settlement and tilt of the footings, so that fly ash can be successfully used as foundation material. Total 36 tests were performed both on fly ash and reinforced fly ash. For tests in optimum moister content (OMC) condition, tank of size 630 mm x 500 mm x 600 mm is used and for tests in submerged condition, circular tank of size 550 mm x 1000 mm is used. Geogrid of Netlon product is used to reinforce the fly ash. Geogrid material has high tensile strength, non-corrosiveness, temperature resistance and biological resistance. A specially designed loading device is used for the application of eccentric-oblique loads developed by Murty (1967). The values of eccentricity ratio (e/B) to width of footing were kept as 0, 0.1, 0.2 and the inclination with vertical were kept as 0°, 10°, 20°. The pressure-settlements and pressure-tilts curves for different load combinations are plotted and the ultimate bearing capacity, settlement and tilt are obtained both in case of unreinforced and reinforced fly ash. Further from this data the non-dimensional charts are developed to evaluate the ultimate bearing capacity, settlement and tilt of the footings. Comparison of data has also been done with unreinforced and one layer reinforced fly ash,