Standard Penetration Values less than 10 blows/ft
Standard Penetration Values less than 10 blows/ft
(OP)
Our geotech expert has taken another position and hard to get a hold of. He recommended that a geotech expert be in contact if the soil report shows standard penetration values less than 10 blows/ft. What should we be doing on these areas of the site to work around or correct this problem. There will be a wall and column foundations as well as traffic and parking potential.





RE: Standard Penetration Values less than 10 blows/ft
RE: Standard Penetration Values less than 10 blows/ft
RE: Standard Penetration Values less than 10 blows/ft
I firmly believe that you can get a good one-man band to work with that will be reasonable. But, rightly said, you should have some background. I would suggest, as a first step to obtain the following texts - Terzaghi and Peck (1967 version), Peck Hansen and Thornburn (geared a bit to structurals), Tang, Tschebotariof, and Tomlinson Foundation Design book (pre-Eurocode version). These are all good practical books that can give you a good basic understanding. Where are you located?
RE: Standard Penetration Values less than 10 blows/ft
I am Located in Ohio.
RE: Standard Penetration Values less than 10 blows/ft
http://www.vulcanhammer.net/download/
www.SlideRuleEra.net
RE: Standard Penetration Values less than 10 blows/ft
Where in Ohio are you located? I might be able to recommend some geotech companies depending on where you are.
Since you mention traffic and parking, the Ohio DOT will improve the soil for roadway subgrades if the blow counts are less than 10. The type of improvement will usually consist of excavation and replacement with compacted granular material, or cement or lime stabilization. Which method used will depend on how low the blow counts are and what the moisture contents are.
Regarding the wall and column foundations, I believe geopiers have been used successfully for a lot of commercial-type buildings. I have not used them myself however. You might try contacting the company at www.geopier.com and talk with one of their engineers.
RE: Standard Penetration Values less than 10 blows/ft
RE: Standard Penetration Values less than 10 blows/ft
I am really concerned at the trend of folks in structural engineering practice not fully appreciating the level of risk they take by trying to solve geotech problems without expert input. Although fees for geotech advice is relatively low, inadequate geotechnical interpretation often results in very expensive, and sometimes embarrassing, consequences. If reading those foundation references BigH suggested was meant to be a replacement to seeking professional geotech advice, I would leave leaving reading them to the experts.
As Panars has suggested, there are several good geotech firms in Ohio.
RE: Standard Penetration Values less than 10 blows/ft
RE: Standard Penetration Values less than 10 blows/ft
I think for the basic sites, it is great to see the structurals learning more, it helps everyone including the client, but the more complicated projects require the specialization of all parties. I would be concerned with any geotech making a blanket statement that uses N<10 as a guideline .... is it a "N", an N1(60) value, as pointed out above, in clays standard penetration is essentially meaningly except in specific applications, etc.
I am not sure why the "one-man" operation recommnedations ... find an experienced geotech that should be involved anyway ! The cost is cheaper than the attorneys fees or the contractors change orders.
Good luck.
RE: Standard Penetration Values less than 10 blows/ft
RE: Standard Penetration Values less than 10 blows/ft
I do agree that the books you discussed are excellent, and refer to them regularly. However my point is the application of the concepts is not always direct and there are nuances ...
I refer to Das and Bowles frequently and have found aspects to be excellent. I had never thought about it from the practical problems perspective.
Thanks BigH for the feedback.
RE: Standard Penetration Values less than 10 blows/ft
This is what happens when non geotechnical engineer makes soil decision. I did a bottom of foundation probe on a residential lot, and recommended undercut depth, removal/replacement and footing dimensions. The client agreed and everything worked out. I also advised him, that the adjacent lot(15 feet away) will be very similar, but more likely a little worse. The client decided it was too expensive to pay my $300 fee and built a house without a soils report. Then he called me to see if we can ok-"they forgot to call you last month ///"! I insisted on an $1100 investigation and once I reviewed the data-They had 6 foot of compressible soils. The client paid for the teardown, investigation, hauling of concrete debris, their client falling behind 2 months and yes he still paid me the $300.
Another note, soil engineering is a combination of science and art and takes many years to develop. The books will give you the fundamental knowledge, but you need years of lab, field, and senior engineer supervision and sometimes input of an engineering geologist before you can design.
A Member of
www.civilvillage.com
RE: Standard Penetration Values less than 10 blows/ft
To everyone else, before I spend next week getting zapped, let me say that the people who take the time to participate in this forum seem to be the sharp questioning people the profession needs, However, as someone who sees a lot of reports, the trend to get the report out and not spend a lot of time addressing what makes the site unique and how to deal with it is hurting the profession and I felt I should say something.
RE: Standard Penetration Values less than 10 blows/ft