This thread is related to my post on ruble trench foundations.

I have been in residential construction since 1987 and just learned how complex soil mechanics can be. Since I almost always work on rural, residential buildings, engineers are rarely involved. The contractors may get plans showing a foundation design, but I wonder if these designs are actually based on site conditions (requiring test borings or test pits) or just rely on rules of thumb for typical conditions. Their is a foundation repair industry so their are obviously problems with some concrete foundations. I am sure the foundation engineering and design of some buildings comes down to what the excavation and/or concrete contractor's opinion, which is probably adequate with experienced people under normal conditions.

I am curious how many readers know what problem soils look like and if this is a topic we should find a speaker to address at a conference. I still have questions about soil engineering and rubble trench foundations.

Have you seen settlement problems? What happened?

Thanks;
Jim

Trouble soil around this area, Central Indiana, is peat. Peat is decomposed organic matter, and peat ground is usually lacking in a subsoil or at times even a solid bedrock, thus it is swamp.

The problem with peat is that it is highly compressive. A structure built on peat ground will always settle a lot, no matter how big the foundation. That's why roads and other constructions that go across bog land are very often 'floated' rather than founded.

A good example of this is an old school near me built in 1916. This building is a substantial brick structure, built on peat ground (nearly everything around here is) The foundation has shifted a lot since it was built, and it was determined that nothing can be done about it. It's peat, so it will just continue to settle under weight no matter what you do about it.

The USDA has collected a vast amount of data and developed maps of soils in all the states. It could be helpful to learn about the regional soils, and their suitability for building, that you are likely to encounter.

http://soils.usda.gov/survey/printed_surveys/

Another place to check, Jim, and perhaps you have already is the University of Maine. Dana Humphrey has done a lot of work on soil mechanics. I like the use of chipped tires as fill, specifically in road bases, I wonder how it would function as a fill in a trench under a barn?

http://civil.umaine.edu/faculty/dana-n-humphrey/