[Didn't know which category to put this in - feel free to move it if there's a more suitable place!]
I'm going to build a small bridge this summer and I'm considering the foundations. Based on previous foundations (cement-filled oil barrels with railway rails) and existing natural stones, ice is not a major problem, but it should, of course, be taken into account. The bottom consists of natural "crushed stone" which is stable and good. About 40 cm down, it's possible to dig without needing to use a pickaxe. I thought the bridge should be about 1.5 m wide, and the foundations should then be about 1.2 m wide.
I wish to cast the foundations elsewhere to then transport them to the water with a tractor loader. Weight is therefore of some importance.
Option 1:
This idea consists of a larger concrete block that is buried and two round posts (200mm diameter) that stick up and support the wooden bridge. Weight about 680kg if I've calculated correctly. Would it be possible to use pre-cast posts instead? The price is almost exactly the same as casting them myself, but it saves some work. Reinforcing pre-made posts could be problematic, though.
Option 2:
This variant is larger and heavier (about 980 kg) and is buried just as deep as the above, but does it offer any advantages over option 1 that justify the higher production cost?
I'm unsure how best to proceed and hope to get your opinions!
