Recurring settlement
Recurring settlement
(OP)
I am located in northern Alberta, Canada. I have been approached by someone with a peculiar problem on his property. Over the course of the winter, the front of his property subsides, anywhere from 10 to 30cm. This settlement then starts to disappear in spring following the thaw, and by mid-summer the ground has completely recovered. Started happening approximately five years ago. This past winter he tried to keep the snow off the yard, and the settlement was less pronounced (~10cm instead of the typical ~30cm). House was constructed in 1996. The location of the lot services doesn't coincide with all of the area of settlement, so I'm hesitant to suggest that's the cause. He feels it may be related to the neighbor's concrete driveway (which is adjacent to the settlement) being poured on bare clay instead of gravel, and is reportedly pinned to the house. While the driveway does show some cracking, nothing suggests to me there is significant heave there, and I find it unlikely a concrete slab would cause a settlement.
Any suggestions? I'm rather stumped by this one.
Any suggestions? I'm rather stumped by this one.





RE: Recurring settlement
RE: Recurring settlement
RE: Recurring settlement
RE: Recurring settlement
RE: Recurring settlement
RE: Recurring settlement
The grass is cut fairly short on the right, and the ground seems to be a similar elevation to the driveway and sidewalk. I do find it odd no adjacent properties exhibit the same behavior, though I suppose if there was imported material (the white mark on the sidewalk aligns with the CC for the property) it might explain different material being present. Any theories as to why expansive clay (if that's what it is) would only start doing this 5 years ago, when it would have been placed 19 years ago?
RE: Recurring settlement
Those trees do not look sufficient large to be of consequence for affecting expansive soil.
That CC trench might have been backfilled with clean sand. That material does not heave.
Looking at the two pictures, I'd say the sidewalk is higher in the winter with respect to that pole. And the low area only slightly up.
RE: Recurring settlement
RE: Recurring settlement
Where snow is present, that serves as a form of insulation. So, paved and areas clear of snow will heave more than those covered with snow. So removing snow from the site of "sag" results in less "sag". That is explained by you allowing that "sag" to heave more than the nearby snow covered area, but heaving some, appearing to be less sag. So, the "settled" or "sagged" areas really just have not moved, while uncovered driveway and walks heave in winter. In Wisconsin we have that same situation.
How do I collect on the bet???
RE: Recurring settlement
Two small items that are keeping me from buy-in: no other yard in the neighborhood seems to exhibit the same behavior, and this yard didn't exhibit it for at least 5 years (current owner has had the place for 10).
RE: Recurring settlement
Trying to figure what went on during construction as to soil conditions at other lots, is unlikely to be of use here. Backfills to trenches Amy or may not be done per specifications
Anyhow use that light pole for a reference and see what happens in the future. A carpenter's level along with a straight board should suffice.
RE: Recurring settlement
RE: Recurring settlement
The rise of water from below with respect to what may come from, above can be quite variable. While the use of the term capillary rise for part of it is not totally right (formation of frost lenses is tied to mineralogy of the soil more so than capillary rise), that's good enough for us here. My measurements of heaving, etc. show that a water table within 5 feet of grade has an effect, but not much if it is lower. That also is a variable from year to year.
RE: Recurring settlement
With snow on the ground and not melting, there is little liquid water for uptake in the tree. The tree needs water even though its growth might be dormant as there is dehumidifying with the cold. Therefore, the tree takes as much moisture from the soil as it can.....resulting in loss of volume in clayey soils and, thus, settlement.
RE: Recurring settlement
http://treephys.oxfordjournals.org/content/16/1-2/...
Here is a funny story. A friend of mine used to work in a nursing home in Lansing, Iowa. One day we took a trip back for him to see his old buddies. I noticed two of the rooms were unoccupied. The manager indicated he was contacting a geotech firm in Iowa to come and see what is wrong, since the floors had settled and the exterior wall was cracked.
I noted a pretty large tree sitting just outside the wall and related how watering the ground alongside the old high school auditorium at Menash, Wisconsin brought back that settled wall and closed the cracks. Trees outside were drawing water. All noted in summer, by the way. That's one of several I've seen work.
A year later we made the visit again and I see the rooms were occupied and the tree still there. Asking the manager what the geotech firm did to fix it. He said he didn't call them, but decided to try watering the tree. Sure enuff, it did the job and one of my competitors lost a job. I shudda billed him.
RE: Recurring settlement