5. Ballasted Track with Direct-connect Sleepers

      For reasons of energy conservation and environmental policy, ballastless track with elastic sleepers has been adopted as the track structure in areas such as grade separations. However, this type of track has disadvantages over vibration-reducing slab track, such as higher construction costs and inferior track bed workability. A new ballasted track with direct-connect sleepers was therefore developed (Fig. 1). This type of track combines the advantages of elastic sleeper ballastless track with those of ballasted track. The whole track structure is supported elastically by fixing the track to the track bed using sleeper bottom pads and variable percolation pads, and the horizontal load is supported by ballast spread around. This leads to a reduction in vibration and noise, and simplifies the track bed bar arrangement work resulting in an expected cost reduction of about 10 %. The conventional work of track re-alignment is no longer required.
      To check the reductions in vibration and noise, a test track was arranged on an elevated bridge, and motor car vibration and noise were measured. On ballasted track with direct-connect sleepers, the vibration acceleration level in the rear center of the elevated bridge was about 7 dB less than that of the slab track constructed alongside; a reduction in structure noise can therefore be expected. The vibration level at a point 2.6 m from the elevated bridge was also reduced, at about 6 dB less than that of the slab track (Fig. 2).

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