where L: the load coefficient which indicates damaging force due to train load conditions (train speed, passing tonnage, etc.)
M: the structure coefficient which indicates track strength due to differences in the track structure
N: the condition coefficient which indicates the track condition (soil content in the ballast, rail age, etc.)
Track deterioration progresses proportionally to the deterioration coefficient.
These coefficients are used to investigate the degree of track maintenance needed relative to future transport, whether the required construction can be performed and what structural strengthening is required.
2.4 Track Economy
Track strength differs according to a combination of factors involving, for example, rail weight, sleeper type and spacing, and ballast type and thickness. These elements act together to effectively withstand train load and deterioration.
Track strength and the amount of track maintenance work are inversely proportional.
Theoretically, the ideal structure keeps the total of capital outlay for the track structure and restoration costs such as material replacement down to a minimum. However, given changing economic and social conditions, this is difficult to realize. It would be advisable to classify railway divisions into grades according to forecast transport volume, and then determine the track structure for each grade. In Japan, railway divisions are classified into 5 grades.
In addition, looking at changes in transport, improvements to the predetermined track structure should be made as necessary.
3 Track Countermeasures
3.1 Strengthening of Track Structures
The three factors of train load damaging force, track structural strength and labor for track maintenance work must be well-balanced. A track structure that is too resistant to deterioration results in increased capital outlay. However, if the structure is too susceptible to wear, repair costs rise. The ideal structure is one in which the sum of both costs are kept to a minimum. Therefore, increases in transport volume, higher speeds and other changes call for improvements to track structure.
An effective and economical method of strengthening track structure should be chosen, looking at one or several of the following.
