Rehabilitation technologies and construction methods
Several useful techniques have been developed by scientists, industry or railway companies to improve or reinforce ballasted rail substructure. These include; cleaning or replacement of the ballast bed; insertion or recovery of the protective layer; and upgrading by lime, cement, mechanical activity or insertion of the geosynthetics). The efficiency of each method greatly depends upon selection of the appropriate method for a particular problem or purpose. For adequate selection factors like geography, geology, climate, type of defect or failure, and the availability of raw materials, costs of planned activities, etc., must be taken into account. It is clear that an integrated approach to selecting the most efficient method is needed.
A key issue for this project is that there is no accepted method of predicting the rate of deterioration of a railway track. Consequently, this means that there is no method of predicting the benefits of any proposed action, which is a very damaging situation in terms of the long-term development of the railway industry. Potential actions which could reduce deterioration rate include: (i) use of geogrid reinforcement; (ii) changing the stiffness of rail seat pads; (iii) use of sleeper pads; (iv) asphalt underlays; and (v) tightening ballast specification. Even without any innovations, there is no method of predicting the effect of changes in subgrade stiffness, nor the effect of axle load, train speed, suspension stiffness, track quality, sleeper spacing or rail section.