A STUDY ON PLASTIC SHEET REINFORCED FLYASH EMBANKMENTS

Abstract

It becomes necessary to construct embankments when it is required to raise the grade line of a highway above the existing ground level. Construction of embankments requires large quantity of material as well as large investments, if the conventional methods of construction are used. The alternate is to use low cost techniques by using industrial wastes like fly ash, available enormously and almost at free of cost, which otherwise causes environmental and disposal problems. At present in India the production of fly ash is about 100 million tonnes per annum and its utilization is 13% only. During the last two decades, some embankments have been constructed using fly ash in India. Embankments of flyover bridges in Delhi (Nizamuddin Bridge and Visvesvaraya Setu), roads at Raichur, Delhi, Kolkotta, Dadri, Ramagundam and Vishakapatnam have been constructed using fly ash. Delhi Metro is also using fly ash for land fill & embankment construction. It is often required to stabilize and reinforce the structurally unsound soil to bear the traffic. Based on comprehensive experimental and research programmes undertaken in developed countries non-metallic materials may be suitable for reinforcement. Geosynthetics are being widely used in highway engineering, to solve a variety of problems related to drainage, separation and reinforcement. Geomembranes are second largest group in geosynthetics, they are impervious thin sheets of rubber or plastic material used primarily for lining and covers of liquid or solid storage barriers. In the present study, a series of lab, field CBR tests and plate load tests were conducted on fly ash in combination with Roorkee soil (locally available soil). These tests were conducted on the above material with and without plastic sheet reinforcement to see the reinforcement effect imparted by plastic sheet. The plastic sheet reinforcement is also kept at varying depth and the tests were conducted. It was observed that the CBR of the above material is improved when plastic sheet, was placed in it. Maximum increment in CBR was achieved when plastic sheet is placed at a depth of 5 cm. from surface. The introduction of plastic sheet reduced the deformation and increased the iii bearing capacity as was revealed by plate load tests. The direct shear test is conducted on fly ash to find out the shear parameters. The triaxial tests were also conducted on fly ash. These tests were conducted on the above material with and without plastic sheet, and to see the reinforcing effect on shear parameters (C and cb). 1