Cause of Foundation Settlement?
Cause of Foundation Settlement?
(OP)
I recently looked at a foundation settlement problem at a 40-50 year old house. The house is located at the bottom of a hill and an approximately 6-foot diameter storm water drain passes through the side yard about 25 feet from the side foundation walls. Soil is silt/clay. The only history I have on the house is that the foundation walls were painted after as fire occurred in 1995. Since that time (and possibly before) there has been excessive settlement at the side of the foundation closest to the storm water drain. Based upon limited exploration I believe I hit a layer of weathered rock approx. 5 feet below the basement floor slab. Since the foundation is supporting the house by arching over the settled area there is not much load on the foundation. Erosion or piping seems like a possibility, but I did not think this would be likely with this soil. Of course, owners have little money to spend to evaluate and repair. I have attached a few photos. Any thoughts would be greatly appreciated.





RE: Cause of Foundation Settlement?
If a ruin is not enforced by the council, with a proper assesment, whilst you should recommend any measures laeding to prevent any sudden loss of life at the property. Maybe you can make use of the strong points towards which the arcing action discharges for placement of some micropiles themselves to support a new frame holding everything above whilst the central settlement is dealt with. Then the central part can be injected with liquid grout at the dry season, too dear everything, anyway. Also you can support a new slab on the ground on foams of enough resistance to compression etc.
RE: Cause of Foundation Settlement?
RE: Cause of Foundation Settlement?
Perhaps the owner of the storm drain can be contacted and asked to be responsible for the problem and the fix.
I'd suspect that the storm drain is corrugated steel having lost its galvanizing.
Can you get inside the pipe to view it?
RE: Cause of Foundation Settlement?
I would like it to be due to the storm drain, but have not been able to tie it in yet. The owner contacted the municipality and was ignored so far. The drain is concrete. I walked the drain. Some small signs of infiltration at joints, but not much. There is significant deterioration right below the street inlet, but the pipe is still intact. Some Photos attached.
RE: Cause of Foundation Settlement?
I am wondering if the storm drain is broken allowing the ground to become saturated and increasing the lateral soil pressure, causing the ewall to fail laterally. With clays, if they were dry over a long period and became saturated, they can expand - hence even more lateral pressure.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: Cause of Foundation Settlement?
when was the drain installed and was it before or after the settlement started?
does the fire have anything to do with settlement?
is the soil mostly silt or mostly clay? is it plastic? how does the addition of moisture to the soil affect the strength?
Is the foundation acceptable or under-designed? What is the quality of the house construction?
is the storm drain pipe surcharged (does it flow under pressure), does it flow constantly, how much flow?
could exfiltration through the pipe joints be introducing water near the bottom of your footings? are the pipe joints gasketed?
how about general drainage around the house, is their any concentrated drainage towards the sinking side of the house? where does the water from on top of the hill drain, towards the house?
what level is the groundwater?
any other utilities such as waterlines or sewers?
any settlement over the storm drain itself? how about excessive vegetation over the storm drain?
any excessive large vegetation near the settled side of the house?
RE: Cause of Foundation Settlement?
RE: Cause of Foundation Settlement?
RE: Cause of Foundation Settlement?
RE: Cause of Foundation Settlement?
Is there a drainage basin in between the storm sewer and the house drain pipe (from the down spout). It's not clear at which point the house drain pipe was disconnected. I am thinking is there any chances the silt was washed into the storm pipe/drainage basin due to back-up of the flood dowstream.
RE: Cause of Foundation Settlement?