Hello,
I have read all the good advice in the thread about jetties/cribs.
Our jetty currently stands on 6 larch poles for the past 30 years, but the ice pushes them up, and it's difficult to press them down. There are boats passing in the shipping lane further out creating waves that lift the ice, and the jetty follows despite its weight, it's about 60 sqm.
Now I am going to demolish it and build a crib. The crib will be made of concrete walls with sides about 2x3 meters.
The depth furthest out is only about 1 meter. Then there is 1.3 meters of clay down to the bedrock.
My question is why you often see that the cribs are built with straight sides. Why not make the whole crib slightly conical so that the ice "loses its grip" when trying to lift the whole thing?
Bmrh
I have read all the good advice in the thread about jetties/cribs.
Our jetty currently stands on 6 larch poles for the past 30 years, but the ice pushes them up, and it's difficult to press them down. There are boats passing in the shipping lane further out creating waves that lift the ice, and the jetty follows despite its weight, it's about 60 sqm.
Now I am going to demolish it and build a crib. The crib will be made of concrete walls with sides about 2x3 meters.
The depth furthest out is only about 1 meter. Then there is 1.3 meters of clay down to the bedrock.
My question is why you often see that the cribs are built with straight sides. Why not make the whole crib slightly conical so that the ice "loses its grip" when trying to lift the whole thing?
Bmrh
Yes, the old log cribs on the coast in Norrbotten were often conical so that the ice wouldn't lift them. Now they have rotted away. However, concrete structures remain, which in most cases have either cracked or sunk, making them crooked.
Thanks for the feedback. My contractor says that he usually places the coffins either on ground cloth or on a reinforcement mat. Additionally, there are steel pipes down to the bedrock at each corner. This is far inside Lake Mälaren (Galten), but the waves under the ice from the ships towards Köping still cause issues. As mentioned, it's built from concrete elements that are to be joined at the corners with heavy flat irons bent 90 degrees and bolted through the concrete. What do you think?
Under similar basic conditions, I have participated in quay constructions where we drilled down well casing pipes a few meters into the bedrock and filled them with concrete as a foundation. The pipes are then allowed to protrude through the clay and water. These quays have held up well and were easy to construct. Well drillers are usually available in most locations. The technique should work just as well for a dock.
The foundation is important. Then it depends on whether you want to invest so that it lasts 20 years or a hundred years. Drilling into the rock does sound reassuring at least 