IMPROVEMENT OF GROUNDS SUBJECTED TO CYCLIC LOADS

Abstract

Due to rapid industrialization, large scale infrastructure development is taking place worldwide. This includes railways, high speed highways, elevated roads etc. To meet the demands of society and industry, many innovative techniques are being developed. Some new materials have also been developed. For railways applications in USA and Japan, new material like geocells, geogrids are being used successfully to enable fast movement of vehicles. The research work aimed to develop design methodologies for improvement of grounds subjected to moving loads caused by trains, vehicles, movement of aeroplanes on taxiways etc. In the research work, model tests are made to simulate the field conditions using newly developed materials like geosynthetics, geocells etc. Since the grounds subjected to moving loads are under the impact of cyclic loads, hence the same type of test was conducted under dry., and saturated condition. The model tests results have been validated by numerical modeling, using FLAC3D. The ballast and its engineering behavior have a key role to govern the stability and the performance of railway tracks. Deformation and degradation behavior of ballast under static and cyclic load tests was studied based on strip footing test. The report presents a study of the effect. of geo-synthetic reinforcement on the (cumulative) plastic settlement, of point loaded strip footing on a thick layer of granular aggregate overlying different compressible bases. Furthermost, the prospective use of different types of geo-synthetics to improve the performance of fresh and recycled ballast was investigated. The research findings showed that inclusion of geo-synthetics significantly improves the performance of ballasted tracks and reduces the foundation area. If the area is kept same more (higher) speed trains can be allowed to pass through the same track. Similarly, area of machine foundation may also be reduced where geosyntheics is provided in foundation.