Also, where do you get the material from?
Sand would have to be mined on the surface, and good sand can be quite useful for glass & concrete... though I guess dwarves might not have that so easier for them.
Ideally it'd be some inert waste but idk if eg. slag would be any good.
Also, obligatory Practical Engineering https://www.youtube.com/watch?v=RZg1zOKm5wk