EFFECT OF RANDOMLY DISTRIBUTED FIBERS ON FLY ASH EMBANKMENTS

Abstract

Due to industrialization and rapid economic growth, demand for electricity had risen tremendously. To meet this demand a number of coal based thermal power plants have been set up. Fly ash is a waste material of coal combustion in thermal power plants. Fly ash is causing environmental pollution and requires large areas of precious land for disposal. Due to increasing awareness of the ill effects of pollution, utilization and safe disposal of ash generated at thermal power plants has become an urgent and challenging task. Fly ash can provide an economical and suitable alternative to good earth for construction of roads and embankments. The conventional soil improvement techniques are generally expensive, involving large quantity of costly materials and construction operations. There is need to explore the possibility of strengthening of low cost material by using reinforcements like geogrids, geotextiles and discrete fibres. It is often required to stabilize and reinforce the structurally unsound soil to bear the traffic. This dissertation report presents the effects of inclusion of polypropylene fibres with fly ash. Laboratory CBR tests, triaxial tests, plate load and field CBR tests are selected as the basic engineering tests to investigate the effects of fibre inclusion in the strength and behavior of fly ash. Tests were conducted on fly ash with different percentages of polypropelyne fibres. Laboratory CBR tests were conducted on fly ash in both soaked and unsoaked conditions. CBR value of fly ash increases with increase in fibre content in both soaked and unsoaked conditions. Percentage Increase in CBR value is higher at lower % fibre content. Triaxial tests were conducted at optimum moisture content with 0.7, 1.2 and 1.8 kg/cm2 of confining pressures. Addition of fibres with fly ash there is no significant change in cohesion value, but angle of internal friction increases with increase in fibre content. Based on the CBR values and shear strength parameters 0.5% fibre content gives the optimum results. Plate load and field CBR test were conducted on fly ash and fly ash with 0.5% fibre content. Modulus of subgrade reaction and field CBR values revealed from these tests. Addition of fibre to fly ash there is lot of improvement in CBR value, angle of internal friction and modulus subgrade reaction.