Indeed, very nicely done, the gentle slope does provide the illusion of depth.
there are only two things I would suggest to improve it.
- Using some sand to make the earth sections look a bit more like spoil rather than spackle.
Placing the wire fence further from the trench.
Unless the Spanish army was particularly daft I'm sure they would have followed the standard military approach that linear obstacles like wire need to be well in front of your positions. In this case, whilst they might slow or impede someone entering the trench they won't protect the blokes in from being shot at by chaps at the fence itself. The modern injunction is that it is always beyond grenade range.