Proceedings home preface contents authors keywords copyright reference ©2012 Civil-Comp Ltd				Paper 134 Modeling Shakedown Plastic Strains of Subballast and Subgrade Materials in the Concrete Slab Track System of High-Speed Trains Y.H. Jung1, C.Y. Choi2 and E. Nsabimana1 1Department of Civil Engineering, Kyung Hee University, Republic of Korea 2Infra-System Research Group, Korea Railway Research Institute, Republic of Korea Keywords: shakedown, subgrade, concrete slab track. full paper (pdf) - reference Recently, the Korean Government is driving a research and development project for a high-speed railway system which is capable of operating at the maximum speed of over 400 km/h. Besides the vehicle system, the track and railroad system should also be built properly to cope with the sustainable operation of the high-speed trains. The concrete slab track system is being introduced to reduce the cost of frequent maintenance in the conventional ballast track. This introduction also demands a new geotechnical assessment of the performance of the subsoil materials. It is important that cumulative plastic strains in the total operation period can be estimated and controlled. The stress distribution in the subsoil materials beneath the concrete slab track becomes more sophisticated than the ballistic track system. The shakedown phenomena, in which the permanent deformation rate at a number of load cycles has become negligibly small and the cyclic response has become elastic, should be understood for better design of railway track. This study, presented in this paper, investigates the pattern of the development of the shakedown plastic strains of the subsoil materials subjected to dynamic loads induced by high-speed trains on the stiff concrete slab track system. A shakedown plasticity model that captures only the envelope of the maximum plastic deformations generated during the cyclic loading process was developed. The model parameters were estimated using the empirical relationships based on the experimental data. The accumulated plastic displacement measured in a series of full-scale model tests was compared with the predicted results using the proposed shakedown model. The predicted plastic displacement shows a reasonably good agreement with the measured values. Experimental investigation, is still required, into the shakedown plastic behaviour of geomaterials used in a high-speed railway track to enhance the proposed model.