maxi-model
UK/US/ROW steam narrow gauge railways 1:1
If you are back filling with earth make sure you have good form of separation between the track bed and bordering earth beds - a "bund". My track is the basic "floating" laid on ballast at ground level. In other words it is surrounded on all sides by earth. Out of necessity the entire track bed, both sides, has a separation using metal or plastic lawn edging. It is left ever so slightly proud of the surface to stop the ballast running away or the soil encroaching. The only little problem is some birds do like to do a little digging around the border area, displacing earth and ballast. Some days you just can't win. Max