An old dilapidated jetty by a lake is to be demolished and a new similar one built in the same place and at the same height.
The water depth varies but is currently 0.5 - 1 meter at the far end and almost reaches the jetty. At low water, there's about half a meter of air under the jetty, but the outer anchoring will always be underwater.
I haven't examined the bottom yet, maybe there's bedrock underneath, but what is visible is a variety of stones in different sizes.
I haven't worked much underwater before, so what I'm pondering is the anchoring on the outer edge.
* Drill with a long rock drill (so the machine is above the water surface) into large stone or bedrock at the bottom. Use a bracket and then a pressure-treated post or metal beam?
* Concrete form and cast a footing?
* Fill with stone?
- Is there chemical mortar that works underwater?
- How do you cast a small footing underwater?
I am leaning towards making two small stone chests, one in each corner of the dock (at the outer edge). I will get back to you after I have examined the bottom and how much it slopes and what lies beneath 🤔
A stone pier is certainly a good option when there is so much rock and stone nearby. Another option could be to have the stone piers as support further in and then fix the inner part of the pier in the ground (and have a longer overhang outside the support/stone pier). Perhaps it is possible to avoid having support in the water.
A stone box is certainly a good option when there is so much rock and stone nearby. Another option might be to have the stone boxes as support further in and then fix the inner part of the dock to the ground (and have a longer overhang outside the support/stone box). Perhaps it's possible to avoid having support in the water.
Smart idea. Though it's water all the way in, the dock will extend up to 2.6 meters at most. I'll probably have to place the stone boxes where the bottom allows it, and hopefully with some overhang. And on land, it should be anchored anyway, so I think this little beauty can be made stable no matter how you do it.
I'm considering casting in the stone box with that water-resistant concrete. But then you need something around the box. I read about someone who placed the entire stone box in a one-cubic meter water tank with a sawn-off lid. But if you're not casting, there's hardly any point in it.
Another thought, if the bottom slopes, is to drill some holes down there and insert stainless steel rods of some kind. But that's probably only good if you're casting a bit at the same time.
What are the conditions at the location? Is it accessible by car? Is there electricity? Should it be expensive or cheap?
The best option is to ensure that all anchoring points are out of the water, as it becomes more sustainable this way. The next best option is a stenkista. Why not just make the whole dock a stenkista and top it with decking?
What are the conditions at the location? Can you drive up to it? Is there electricity? Should it be expensive or cheap?
The best is if you can make sure all anchor points are out of the water, it's more sustainable that way. Next best is a stone crib. Why not just make the entire dock a stone crib and top it with decking?
There is electricity, and you can get about 10 meters away by car. But a bit steep the last few meters so a bit tricky with an excavator or similar.
And the idea is to keep costs at a reasonable level, whatever that entails?
Stone is heavy and would be nice to avoid bringing stone there and also avoiding an excavator. That's why I'm considering having two smaller stone cribs instead. But we'll see where we end up in the end. The dock is 6.5 meters long, so a stone crib 6.5 x 1 meter and let's say 0.6 meters deep would mean 4 cubic meters of stone = 6 tons. Not impossible but maybe a bit unnecessary? 🤔
How did you solve this in the end? I have a similar situation where one outer corner of the dock stood on a pillar until last winter when the ice pushed it away. The pillar doesn't seem to have been attached to the stone it stood on.
I was thinking of replacing it with a similar solution but attaching some iron as anchors in the bottom of the pillar. Right now, the water level in the lake is low and the stone I intend to cast on is 5-10 cm below the water surface, but more normally 30-40 cm.
How did you resolve this in the end? I have a similar situation where one outer corner of the bridge was standing on a pillar that the ice pushed aside until this past winter. It seems the pillar was not attached to the rock it was standing on.
I was thinking of replacing it with a similar solution but with some metal anchors at the bottom of the pillar. Right now, the water level in the lake is low, and the rock I'm planning to cast on is 5-10 cm below the water surface, but more normally it is 30-40 cm.
To cast underwater, you should use a 110 mm drainage pipe sealed at the end with a cloth. Fill a little concrete in the lower part of the pipe. Then tilt the pipe slightly underwater and quickly turn it down to the bottom/anchoring. The pipe should stand firmly against the ground and be filled with concrete. Getting the concrete out is easy, but only a little at a time. It spreads out at the bottom and gets a bit slushy. Just keep adding more, and it's enough to shake the pipe gently.
The pipe must be filled with concrete, otherwise, water will enter from below and ruin the concrete. The weight of the concrete holds back the water, so the water pressure won't push up. I've cast at a depth of 3 meters in a concrete ring. If you have concrete rings, seal the gaps against the bottom/rock by pressing cloth into the gaps, then pour a bit of concrete onto the cloths. Wait a few hours or until the next day for the concrete to set. However, many cloths are needed. The smallest gap allows the concrete to rush out quickly under a concrete ring, and it's unstoppable once it's started.
The concrete should come out under the existing concrete and spread out; otherwise, the concrete becomes like water, and the cement leaches out immediately.
I don't have any pictures here now, but the solution was to build crib docks with pressure-treated lumber of the highest quality, placed a bit out in the water. Around 1 x 1 x 1 meter that we filled with LOTS of stone.
On the inner side, I drilled with a rock drill and attached post bases with anchor adhesive under the water.
Then beams between the crib docks on the outer edge, and between the post bases on the inner edge.
There was a bit of height adjustment since it's difficult to get the crib dock's wooden beams to align exactly in height.
Finally, we framed between the beams and put decking on top as usual. I've heard nothing other than that the dock is still in place 😜
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MathiasS said:
tommib said:
