Eurailpool Image Video (dt) 

There is an English version too: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-SlFQQcVnWzU.html

@Jim Jardine These are geotextiles. In railway construction, they are used to protect the base layers of the track bed from the fact that fine components of the soil such as clay try to migrate up into the base layers and the ballast and pollute it and destabilize it due to then higher water holding capacity and resulting sludge. They increase the load-bearing capacity of the soil on which the track body is built, the grid mat, to see @ 03:53, thereby increasing the tensile strength of the underlying geotextile

هيبة العراق 5mio

you con also get al look at the english version