Settlement calculations for organic soils
Settlement calculations for organic soils
(OP)
A bit about the project: An existing facility in New England located adjacent to a river is looking to build an addition with full basement onto an existing building. The finish floor elevations will be the same, and the new building basement will be accessed via the existing building's basement. In preliminary discussions with the client, we became aware of settlement issues at the existing building. After drilling, we discovered a loose organic silt/sand layer on the order of 5 - 8 feet thick at a depth below the proposed subgrade that makes it impractical to remove prior to construction. Cost is king, and piles are expensive. Add to that the existing building is NOT on piles, and we're left trying to figure out how to determine settlement of the organic layer under both the existing and proposed building sections. Any method / computation suggestions for how to evaluate this potential settlement and differential movement between the two buildings? Thanks in advance for any help!
- 4lbSledge
- 4lbSledge





RE: Settlement calculations for organic soils
Good luck. Others should be able to provide better guidance.
RE: Settlement calculations for organic soils
Our main concern was how to evaluate settlement of organic soils should the client decide against helical piers for some reason. I've seen a lot of information on calculating settlement of high organic content layers like peat, but nothing that suggests how to approach a layer with only 4-5% organic content. The organic content may be negligable in this case, but it never hurts to have calculations to back up that assumption :)
RE: Settlement calculations for organic soils
RE: Settlement calculations for organic soils
If you are building with a similar structural system as the existing (mat/raft slab), you might try to determine how soils under the existing have performed. If there are survey benchmarks for comparison.
Also, you mention being next to a river, so consider that you may lose soil volume due to expression of water under the new weight of the building (or float the new building if too light.) Or, if the building is on soil higher than the river, is there a soil stability issue to deal with?
RE: Settlement calculations for organic soils
Thanks
RE: Settlement calculations for organic soils