16. Method for reducing the frequency of maintenance on standard longitudinal sleepers at boundaries with structures

Due to the sudden change in track support conditions, maintenance frequency tends to be higher at boundaries with structures, such as open channels that cross railway tracks and transitions from embankments to girders, than at other sections of line. The use of longitudinal sleepers is an effective way of reducing the labor required to maintain ballasted track.
However, since such sleepers have hardly ever been used at structure boundaries, their effectiveness for this purpose remained unverified.
In light of this, we conducted numerical analysis and full-scale testing to design a method of laying longitudinal sleepers at boundaries with structures, as well as to devise standard longitudinal sleeper structures to suit a variety of conditions (Fig. 1).
At the same time, we verified the effectiveness of longitudinal sleepers in reducing longitudinal level irregularity in a test installation on a commercial line (Fig. 2).

More specifically, we proposed three laying methods—laying longitudinal sleepers before and after an open channel (Method 1); laying them across an open channel (Method 2); and positioning the end of longitudinal sleepers on an abutment (Method 3)—and designed a standard longitudinal sleeper structure for each method.
In this way, once the laying method is determined, the appropriate kind of longitudinal sleeper can be selected without the need for any special design.
The results from a test installation on a commercial line using Method 1 and measurements of longitudinal level irregularity proved that the rate of increase of longitudinal level irregularity with longitudinal sleepers is five times lower than with conventional sleepers, thereby making track maintenance unnecessary for 22 months (track maintenance was omitted six times in two years).
Previously, track maintenance with conventional sleepers was necessary three to four times a year.
Thus, installing longitudinal sleepers in sections that require frequent track maintenance makes it possible to significantly reduce track maintenance costs.