Dynamic characterisation of a ballast layer subject to traffic impact loads using three-dimensional sensing stones and a special sensing sleeper

Spectral analyses, based on field measurement of dynamic response of the ballast layer subject to traffic loads, evaluated the dependency on frequency regarding attenuation effect and strength of ballast layer. The measurement was conducted by using high-performance three-dimensional acceleration sensors and a special sensing-sleeper, which was assembled to assess the dynamic response loads acting on the sleeper bottom at a wide frequency domain. The measured results confirmed that for impact-load components over 100 Hz, the ballast layer resists because of its high rigidity and can reduce the impact loads substantially. However, the ballast layer is almost non-resistant to the low-frequency load components, which are not reduced enough. The finite element vibration analysis of the ballast aggregate, whose ballast stones are expressed as a polyhedron model using a three-dimensional discrete element method, examines frequency characteristics up to high-frequencies and clarifies the stress distribution of the ballast and the wave propagation of the ballast stone.