Soils Problem
Soils Problem
(OP)
I have a job where that is on poor soils. This was revealed during the geotechnical investigation. 3 small buildings are going to be placed on this site. The Geotechnical engineer recommended timber piles or PIF to remedy the problem under 2 of the 3 buildings (building #3 can be placed on virgin soil supported by spread footings). The contractor did not like the price of these solutions so he contacted a company that specializes in Rammed Aggregate Piers (RAP). This company came in and did further testing under these 2 buildings and designed their RAP based off of my loads. Construction of the RAP's is now under construction for building #1
We are in the process of designing building #2 of which the contractor is still unhappy about paying to remedy this soil problem. I have just received an email from a 3rd geotechnical engineer (if you count the RAP contractor as geotech #2) stating that he has reviewed the testing borings of the other two and concluded that the building can be supported by virgin soil on spread footings.
Being responsible for the design of the spread footing and building... should I be concerned with the fact that the contractor is "shopping" the geotechnical report around to see who would give him the best results? Where would my responsibility end?
We are in the process of designing building #2 of which the contractor is still unhappy about paying to remedy this soil problem. I have just received an email from a 3rd geotechnical engineer (if you count the RAP contractor as geotech #2) stating that he has reviewed the testing borings of the other two and concluded that the building can be supported by virgin soil on spread footings.
Being responsible for the design of the spread footing and building... should I be concerned with the fact that the contractor is "shopping" the geotechnical report around to see who would give him the best results? Where would my responsibility end?






RE: Soils Problem
RE: Soils Problem
Rammed Aggregate piers are extremely competent if no drilling is done to produce the hole. The surrounding soil is densified and the allowable loads are derived with generous Safety Factors.
RE: Soils Problem
I certainly think you should be concerned. I'm not really sure who would end up liable if the foundation system were to fail.
But I say this is tough because I know from experience that some geotech companies tend to operate so far on the side of conservative that they essentially do not have to do any work. Geotech by nature is uncertain, but the higher the factor of safety they use, the less work they have to do.
It is impossible to tell whether the first company was not doing its job and simply being overly conservative, or whether the last company will be proven to be criminally negligible.
Tough call.
RE: Soils Problem
I'm sorry,I should have mentioned that the owner is very unhappy that he bought a poor site and is driving these changes (he seems to be taking it out on everyone). In a weird situation I am providing engineering services for a steel fabricator who is providing design build services to the contractor.
RE: Soils Problem
RE: Soils Problem
RE: Soils Problem
and i've seen plenty of project where the owner went with the cheap geotech and the geotech gave the easy answer of "put it on piles" where spread footings would have worked assuming that the appropriate sampling, testing and analysis were performed. this also assumes that they were actually looking at all aspects of the issue (doesn't do any good to have a foundation good for 6,000psf if the darn thing settles 5 inches...as with soils here, settlement is typically the controlling factor).
RE: Soils Problem
RE: Soils Problem
RE: Soils Problem
one of the things one has to watch out for is letting the contractors lead the project off in to dangerous territory.
and let's also not forget that soils are by far the most complicated "animal" of all the construction materials. you could have two different geotechs look at a site and come to different (but likely somewhat similar) solutions...just take this discussion board for example: you can post a rather straight forward question about a situation on the geotech pages and you'll see a wide range of opinions that all sort of trend toward a similar answer...you also sometimes have the "out in left field" responses...and sometimes thinking outside of the text book can be the most beneficial approach to a project. so i'm not exactly sure anyone necessarily has any explaining to do...sometimes, the more sophisticated approaches may be out of the expertise of a particular firm. there again, it never hurts to ask.
RE: Soils Problem
RE: Soils Problem
I chose the words "explain themselves" poorly. What you are suggesting makes perfect sense. Perhaps "justify their findings" is a better choice of words.