Soils Report Language
Soils Report Language
(OP)
Do Geotech's ever put wording in the soils report that deep foundations or some type of soil modifications are "required" or "recommended".
The reason I am asking is I have a report where a building is going on about 13ft of existing unknown fill. The report is worded in such a way that it neither "requires" nor "recommends" a soil reinforcing system be placed instead of typical spread footings. It just says "as a lower risk option to spread footings" a soil reinforcing system may be used. The reason it gives is more that normal settlement might occur if typical footings are used.
I have done deep foundations before, but I don't remember the report being worded in such a way. But I don't remember it saying piles were "required" either. If you know that some soil modifications must be done, what is the standard way of conveying this in the report?
The reason I am asking is I have a report where a building is going on about 13ft of existing unknown fill. The report is worded in such a way that it neither "requires" nor "recommends" a soil reinforcing system be placed instead of typical spread footings. It just says "as a lower risk option to spread footings" a soil reinforcing system may be used. The reason it gives is more that normal settlement might occur if typical footings are used.
I have done deep foundations before, but I don't remember the report being worded in such a way. But I don't remember it saying piles were "required" either. If you know that some soil modifications must be done, what is the standard way of conveying this in the report?





RE: Soils Report Language
If the site has 13 ft. of existing, inorganic fill that looks decent, but does not have documentation regarding method of placement, compaction, etc., there is always a risk of poor performance.
The structural engineer, the general contractor, the geotechnical engineer, and the owner should have a meeting to discuss the budget issues for each alternative and discuss the owner's tolerance of risk of settlement.
If possible, it is probably worth it to try to find any available documentation of the existing fill.
RE: Soils Report Language
If an owner or engineer asked for specific recommendations for a type of foundation that I did not believe was suitable for the site, then I simply would not give them the recommendations.
RE: Soils Report Language
The problem is that there may be a hungry earth work contractor that has their own gravel pit or sand mine that could do a remove and replace significantly cheaper than a deep foundation. The same is true in the other direction.
The only one that really knows the economics of each alternative is the general contractor and his subcontractors.
The architect and the structural engineer are the only ones who know what magnitude of total and differential settlement the structure can tolerate.
The owner is the one paying the bill and living with the final product.
Therefore, I try to come to some kind of consensus among the project team prior to completing a report. Then if things go bad, they are not all pointing a finger at me. They are all involved in the decision. This also reduces the questions and revisions after the report is complete.
RE: Soils Report Language
1) "Based on the variable, non-engineered nature of the fill, the thickness of the fill and the presence of the loose silty sand to sandy silt below, spread foundations are not considered suitable for the support of the roof or head frame structures. It is recommended that foundation support be derived from deep foundations driven to end-bearing in the hard glacial till, the surface of which is approximately 60 ft below existing grade."
2) "From a geotechnical engineering point of view, the most important feature influencing the selection of the foundation system to support the proposed structure is the presence of an extensive deposit of generally loose, heterogeneous fill which extended to depths of about 18 to 22 ft below existing grade. The site is not judged suitable for using spread foundations and it is recommended that deep foundations be utilized to bypass the fill deposits in a positive fashion with a view towards supporting the Addition within the underlying clayey silt till."
RE: Soils Report Language
If the site is not suitable for shallow footings, I say so in couple of areas then give them choice of deep foundation types, depths and geometry.