How does glued ballast work?

[ETMbloke]

How does glued ballast work? When is the glue applied and how much is needed?
Once applied, does it means that the ballast can't be tamped and how is it disposed off?

 

[Russel]

Hmm, not something I've ever thought about, but now I'm interested in knowing the answer myself!

 

[E27007]

Normally the four-foot of the track is not glued, only the shoulder of the track is glued so to stabilitise the track and constrain sideways creep-movement of the track.
The "glue" is a resin and very strong, no idea how it is disposed off, many a railwayman has looked at glued ballast thinking "I wish I could have some for my garden" you do not see weeds in the ballast of glued sections.

 

[ikari2006]

Do you mean something like XiTrack (Balfour Beatty)? As I understand it they inject polyurethane to fill about 20% of the voids in the ballast creating a kind of cage to hold the ballast, whilst the 80% voids allow the ballast to continue to free drain. Glue itself probably wont work due to stresses/loads generated by trains so something semi-flexible is needed. Given it dries to act like a geotextile, I would surmise you cannot tamp it as it'll break/get stuck in the tines. Very difficult to excavate (like geotextiles), probably counts as contaminated ballast and ends up in landfill as costly to clean/treat for recycling. Application could be with new track or on existing (retro treatment; sprayed on/injected) as was done near Keadby Drawbridge. A search engine can give several case studies where Balfour has carried out such works and includes a bit of the theory behind it. Quantity wise I'd expect it to be similar to grout but I'm sure they do calculations on a site by site basis to suit local conditions.