David: It seems disheartening at first but once you get started I think you’ll find you can fix it up pretty quickly. Looks like the rocks had been on the surface, and either they slipped and pushed the mud, or more likely the mud slipped and brought the rocks skating along on top.
Well, you’ve got to figure exactly what slipped and why and how to put a stop to it.
Since there’s nothing on the other side of the track but a trench, you ought to fill that in because gravity is for sure going to fill it in for you my friend.
Gravity will use whatever is closest, in this case, your rocks, that pile of dirt, AND your tracks. And that’s exactly what it has started to do. Another couple of years and that trench will just disappear by natural action. Dirt is lazy. It slumps.
Well, you’ve got to forsee what will happen and take the necessary steps. Don’t lay your track on ground that will move.
You could
a) fill in that trench, as I said, so then there’s nowhere for that dirtpile to slump into.
b) build a retaining wall above the track to hold back that hill, and create a level area below the wall for your track.
c) install those flat rocks so they won’t skate over the surface of your hill there. They weren’t performing any useful engineering function as they were anyway. They look to me as if the’d be better used as flagstones in a walkway.
d) put your track on roadbed, spline or otherwise, as Bob suggested - that would be the simplest, but your earth would still do whatever gravity commands.
If I were going the roadbed route I’d raise my track well above ground level, that’s my taste - up around waist height.
But if you want it close to the ground, fine, just get it above soil level, not right down on the ground like that, where shifting ground will mess you up every year. I’d want to stop that ground from shifting above my track anyway, but at least give the dirt a way of sliding under your roadbed! That means a roadbed, spline or board, but on stilts.
Now Bob mentioned ballast. He was talking about his own ballast, which he says is just decorative.
Like Bob, I don’t think of ballast as a useful item in a garden railway; it’s just decoration as far as I’m concerned, and I don’t ballast my own track at all! My railroad is laid on bricks which I make level on the ground, but not down at ground level.
Each year for the first 4-5 years I raised the track by a couple of brick thicknesses. I also brought in dirt and fill to fill in under and around, so now my track is above knee height. I’d be glad to get it even higher but in my small garden that’s not practical.
I used recycled concrete building rubble that I got for free from demolition sites round here to build walls around this track - most people look at it all and think it’s fancy rocks. I used the same stuff to build up tunnels and cliffs, and then topped it all with a few nice richly textured limestone rocks on top of the hills and tunnels.
The main point is that it took a few years, but now I’ve got my track high, so I don’t have to bend over, dry, and above any dirt except for the dirt I’ve piled in there to make a couple of “mountains”. These mountains are held in place by substantial rockwork.
When you do any rockwork, consider how water will flow, and set the rocks so it flows in a harmless direction. For more about all this, take a look at a book on building rock walls in your garden. My motto is: Do it once, do it right, and never do it again.
By the way, that gravel you’ve got there for ballast - you should use that for a foundation under any retaining wall you decide to build. It’ll allow water to flow UNDER that wall instead of pushing against the wall. Also, as you fill in behind a wall, place gravel first thing behind it so water can slip down the back. Water loves to flow over gravel, not be held back by mud or clay. Consider where your water is going to flow, and create a path or ditch for it that will keep it from going where you don’t want. That path or ditch for the water can also be filled with gravel. The water won’t mind, it’ll just flow right through the gravel. As long as you’ve given it a slope to go down the right direction in that path or ditch. OK?
Good luck with your railway!
That has always been my downfall.