How to seal a conduit with an underground cable?

I put my electrical cable to the garden house, for example, in PE water conduit. It is thus protected from external influences and you wouldn’t scratch the electrical cable right at the first shovel cut. Just as a suggestion: Cost for example 25 meters, 27.00 Euro.

If you can sleep better afterwards, lay an empty conduit. But then immediately KG pipe DN100. Trying to thread an NYY3x2.5² through a 50m M25 is a pain. At the end, the pull wire from LiYCY2x2x0.25 that is usually put in there will more likely tear...

Basically, NYY can be laid directly in the ground; it is designed for that. And they don't just break easily; there are tens of thousands of kilometers of NYY underground all over Germany for decades without problems.

If you hack in full force with a spade or pickaxe, I would be more worried about your health than the cable's. That's why a much, much more important than a protective pipe is an as precise as possible drawing of where and how deep you laid what in your garden.

As already mentioned, put a sealing plug on the end and ideally fix it with construction silicone so that it does not pop out by itself. When laying our 8 empty conduits outdoors, I made sure that the pressure-resistant Kabuflex empty conduit starts as close to the house as possible so that it does not crush the standard conduit during compaction. Then I made sure that there is always a slight slope of the empty conduit away from the house; otherwise, potential condensation water will flow into the house. We then buried the ends of the empty conduits with the opening facing downwards (the lowest point of the pipe) in the ground. Sand on top, then gravel, compacted, done. Oh, and don’t forget the documentation of where the lines run.