The structure transition zone means the stiffness varied area of substructure which holds up bridge-earthwork, earthwork-tunnel, and ballasted or concrete track. In the structure transition zone with stiffness changes, a sudden ununiform settlement is occurred by stiffness difference. Unusual vibrations and impact loadings break out in train in this zone. Therefore, recently, on the point of view of stability and maintenance of track for high-speed railway system, the transition zone should be

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... reated with careful. In this study, the approach blocks to reduce the difference between the stiffness of the support for the plan were investigated. The research results show that the stiffness of transition zone, such as Lightweight formed concrete is considered to be the most appropriate.