soil boring & testing alternative

[TomTX]

Because soil boring and sample testing are relatively expensive for determining how deep drilled piers should be, contractors sometimes drill a test hole as a cheap alternative. The correct depth is estimated by simply noting the type of soil coming up as a function of drilling depth.

Is this practice effective? It would seem that much information is missing and that there is much at risk.

 

[SperlingPE]

I would agree that this is risky.
Soil testing in my area runs from $2000-$5000 for most of the buildings I am involved with. The higher prices are for larger buildings (require more test holes) or for buildings that fall into the essential type category (hospitals, etc.). These projects run from $500,000 to $15,000,000. The cost of doing soil exploration is negligble when compared to the overall cost.
If I was in a position that I would have to follow the procedure you are asking about, I would find the geotechnical engineer who has done explorations in the vicinity and this still would make me very nervous.

 

[ctmtwilliams]

Perhaps your question would work better on the Soils Testing Engineering Forum: Soils Testing Forum

I wouldn't let the contractor engineer a project that required piers, why would I let him do the geotechnical?

 

[MotorCity]

Soil borings are cheap insurance and money well spent (i.e. cheaper than a lawsuit). I would never take on a foundation design without this information, not even a residential structure. If it means that I don't get the job, so be it.

Good luck

 

[eric1037]

If contractors do this they are taking ALL of the risk for the performance of the foundations. If that is a risk they are willing to take, then go for it. If not, they should hire a qualified professional geotechnical engineer to perform a geotechnical evaluation.

 

[TomTX]

Thank you all for your replies. I agree. At least one city in our area requires that a PE design the corrective measures for a slab foundation repair permit to be issued to the contractor. A contractor should not be allowed to install a belled pier system without it being designed and installed properly. The design should be based upon a geotechnical evaluation.

 

[Lutfi]

I would not design a structure without a soils report. Man, soils are tricky even if you get soil borings. In a case near me, tank designer/builder only took one boring to 100-foot depth under a 5 million gallon tank. The tank is sinking and if more holes, and deeper, would have revealed a layer of clay!!!!

Cost of drilling is peanuts compared to cost of litigations and trying to fix structures.

My two cents worth


Lutfi

http://www.cdeco.com