The city is in the process of replacing part of our street.?ÿ They are tearing up and repairing one side of C/L at a time so we have some access.?ÿ
The old concrete was 8" on top of clay.?ÿ The new is 8" on a 1 ft bed of crushed concrete perhaps 1" pieces.?ÿ That will let the plentiful water flow better - we often have water coming out of the cracks even when the lawn is dry. There must be small channels eroded in the clay under the concrete to let it flow.
Unfortunately, they are not doing a total replacement. They have marked to replace the section on both sides of C/L in front of my driveway but not the next slabs downhill.?ÿ This is going to leave a clay dam for the water that is trying to flow down the hill in the gravel for half a block with a fall of several feet.
When that freezes, will it raise the pavement?
Fortunately, the level run I did some years ago shows that the bottom of my sump pit is about 2 ft above the top of the gravel at the "dam", but the underground flow may be unpredictable and that's a lot of possible head on the water from the top of the hill.
When they get done, I'm going to be mightily tempted to drill a hole through their new concrete at the lowest corner.
Stop in and ask them.?ÿ The cheapest fix is before there is a problem.
What head of water does it take to lift a slab of concrete?
If concrete is 2.4 times as dense as water, 2/3 ft of concrete weighs as much as 1.6 ft of water. Any head beyond that will work against joint friction, etc.?ÿ So 10 ft of head will create an outlet somewhere. Will it punch out the soil at the sides or lift the slab?
I expressed my concern to the crew chief, and he just said the gravel was to give the water somewhere to go. When I pointed out that it couldn't flow well under the slab he was standing on, he didn't have an answer.
So 10 ft of head will create an outlet somewhere. Will it punch out the soil at the sides or lift the slab?
Both, and if your luck is anything like mine all the water will flow towards your lot. ?????ÿ
Perhaps would make sense for them to drill a hole themselves (perhaps install a pipe flush with the top...a sort of relief valve)?
If it was me, I would ask to see the geotechnical report, then direct a formal email to the project engineer at whatever municipality and reference the geotechnical report. The guy in the field is unlikely to have any idea.
The hole would have its own problems, like icing up the street in freeze-thaw weather.
Railroads will install slotted pipe below road crossings in cases similar to yours.?ÿ That provides the exit.
Did they put under drain in at the edge of undercut?
I don't see them putting in anything but crushed concrete with a thin layer of finer rock on top, then the new pour.
They use a small roller machine.
Looks like 24 or 30 inches, 2 rollers.
Why not a stick of perforated pipe wher rock meets clay and run it to a storm drain??ÿ
The basic problem deteriorating the street to begin with was that there is no storm drain on this street nor where it meets the cross street at the bottom of the hill, and they aren't adding a drain in this project.
I used to work in Engineering designing roadway reconstruction projects.?ÿ Many of the streets I worked on were concrete with curb.?ÿ Many of the original streets were on clay in areas of high ground water that would bubble through cracks in the concrete slabs, failures and at the curb line.
Using crushed concrete with the idea that water will flow through it is a bad idea.?ÿ The fines in the mixture will rebind after being exposed to moisture, that will block the water from flowing through.?ÿ The drainage method I used was to install under drains (6" perforated pipe) in a stone trench 4' deed where possible with the stone wrapped in filter fabric at the back of curb on both sides of the street.?ÿ The underdrains collected the water from underground and strained it to storm sewer structures.?ÿ The water never got a chance to reach street level.?ÿ Roads that were wet are now dry.?ÿ
Wondering what came of this...?ÿ Too old a thread for any input on the construction phase, but curious how the project wrapped up.?ÿ Any outlet to daylight ever provided for the water under the slab?
We now have a nice smooth street with water seeping out of the joint for most of the width where new meets old. Gonna be fun making the turn into the driveway during freeze-thaw weather.
There is no place else for the water to go, unless it has formed a channel through the clay.