Prairie Boy
Civil/Environmental
- Jul 9, 2024
- 1
Hello:
We have a boathouse built in NW ontario that was installed on 22 helical piles, most of them 4.5" pipe w/24" helicals. The piles are topped with a steel I-beam frame.
The structure is light wood-framed, 24'x28', standing seam metal roof and fibre cement siding, so very low loads. The water depth is about 5' on the lake side and 1 foot or less (depending on water levels) on the shore.
The structure has experienced major shifting since it was built in 2013 - with shoreline piles appearing to heave (up to 9"), and water side piles appearing to sink several inches.
Unfortunately the pile company took very poor records so we only have a very general, anecdotal idea of pile depths.
Their attempts to stabilize the structure includes adding 6 more piles on the lake side, including 3 piles down to "resistance", which we assume is Canadian Shield rock, at a depth of 70'!
Wondering if anyone here has an idea of why a foundation that should theoretically not be failing be experiencing so much movement. I suspect the shore piles are heaving, as some may have only been driven to 8-10' and locals have indicated that frost in our sandy silty soils, especially where snow cover is poor, can be as deep as 8-10'. However - the dropping on the lake side is a real head scratcher.
Thanks in advance!
We have a boathouse built in NW ontario that was installed on 22 helical piles, most of them 4.5" pipe w/24" helicals. The piles are topped with a steel I-beam frame.
The structure is light wood-framed, 24'x28', standing seam metal roof and fibre cement siding, so very low loads. The water depth is about 5' on the lake side and 1 foot or less (depending on water levels) on the shore.
The structure has experienced major shifting since it was built in 2013 - with shoreline piles appearing to heave (up to 9"), and water side piles appearing to sink several inches.
Unfortunately the pile company took very poor records so we only have a very general, anecdotal idea of pile depths.
Their attempts to stabilize the structure includes adding 6 more piles on the lake side, including 3 piles down to "resistance", which we assume is Canadian Shield rock, at a depth of 70'!
Wondering if anyone here has an idea of why a foundation that should theoretically not be failing be experiencing so much movement. I suspect the shore piles are heaving, as some may have only been driven to 8-10' and locals have indicated that frost in our sandy silty soils, especially where snow cover is poor, can be as deep as 8-10'. However - the dropping on the lake side is a real head scratcher.
Thanks in advance!