抄録
This paper describes two newly developed techniques. The first measures the dynamic pressure distribution on sleeper bottoms induced by running trains with frequencies as high as several thousand Hertz using a special sensing sleeper equipped with ultra-thin impact force sensors. This sensing unit consists of a concrete sleeper fitted with a large number of sensors. Attached to the sleeper's whole undersurface is a solid mass made up of 75 thin impact force sensors using piezoelectric film (PVDF). The second technique enables measurement of the three-dimensional (3D) motion of existing ballast stone using a special sensing stone containing piezoresistive triaxial acceleration sensors that can detect frequencies as high as approximately 1 kHz. To achieve this, two accelerometer chips are embedded separately in crushed stone. The average value of the two acceleration measurements indicates the translational acceleration, and the difference between them yields the rotational acceleration. We tested these sensory performances in a full-scale field experiment performed on a railway line. The results confirmed that the newly developed techniques are beneficial for measuring dynamic interaction within the boundary layer between a sleeper and an assemblage of ballast grains, and for assessing 3D ballast motion.
