Keywords: ballasted track, roadbed improvement, full scale test, cyclic loading.

One of the most important functions of ballasted tracks is the ease with which track irregularities can be corrected by using tie-tampers. Good drainage is also an important function for ballasted tracks in order to avoid the occurrence of mud pumping, and to reduce the settlement of sleepers. These functions are ensured by appropriate grain size distribution of ballast material. However, in the aged and degraded ballasted tracks, these important functions disappear.

In particular, on the local railway lines in rural areas in Japan, there are many places where the ballast is not replaced for several decades after the construction of the line. Under such circumstances, it will be very difficult to maintain the degraded ballasted tracks sustainably for further decades. Therefore, new effective maintenance technologies, at a low cost for the ballasted tracks, are demanded.

This paper introduces three different solutions to properly maintain the degraded ballasted track. The first method is a roadbed improvement which recycles the degraded ballast mixed with cement grout together with ballast replacement. The second method is an improvement of the degraded ballast by polymer aqueous solution. The third method is a stabilization of the ballast layer by fine particle cement grout. Which one out of these methods should be selected should be decided considering the condition of the in-situ ballasted track. In this article, results of laboratory tests and application tests at the field are described.

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