Bolehole record

[victor923]

The remark of the bolehole record stated that there was no water encountered. However I am designing a pile foundation near the river. Should I assume the water level to be just under the ground to predict the worst case of it?

 

[Ron]

You should get a corrected geotechnical report. Don't assume anything other than if that information on the report is wrong, the rest of the report is suspect as well.

 

[BigH]

Did the investigation not install a standpipe piezometer that could be read during and subsequent to the investigation? If not, I think they did a dis-service.

 

[oldestguy]

It depends on what the job consists of. Pile foundations may or may not be influenced one way or the other depending on what is to be built. It also depends on the soil type encountered. You should inquire of the drillers and see what they really observed. A quick job of get ind get out may not give the water any time to be entering the bore hole.

For a simple bridge job with one span, it may not mean anything. For a multi- span job with piers in the water, it means something different, mainly for construction. For a building construction job it means something quite different yet.

Also, even though it may be near water, with rather tight soil and a water supply well nearby, that may explain it.

In other words, you don't say enough for anyone to properly help you.

 

[fattdad]

Geology is the key factor here. Assuming that this site has some measurable soil column above the bedrock and the abutments are next to the creek, yes, I'd assume the static water table near the water elevation in the creek. Don't rule out some effect from transient flood levels.

I kind of agree with oldestguy, to what extent is this relavent to a pile foundation? (I'm not suggesting it's not, it's just important to consider.) If there is some relevance, you could include your engineering concerns in a post.

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

All - but why would a geotech leave the question open and not install a standpipe - that was an absolute standard for our firm in Canada. At the time of the investigation, one might not know if a pile or spread foundation will be the choice of support - isn't the purpose of the investigation to characterize the site subsurface conditions and THIS includes the groundwater (or piezometric) level. As fattdad said in another post why guess for the cost of a hundred bucks or so . . .

 

[moe333]

Where I am, the expense of installing a standpipe has become non-trivial. There are additional permits and fees required above just performing a boring, and as per the permitting requirements the standpipe ultimately needs to be destroyed which means another drill rig and inspector mobilization. The information from a standpipe can be very important but the cost quickly adds up. Many will base the presence of groundwater on moisture content/presence of wet soil. It's not the best way to do it (due to capillarity, fluctuations, etc.) but at least it gives you some info. if the owner will not bear the cost of installing a standpipe.

 

[fattdad]

Just for the record, I'da fully considered installing a piezometer from the onset.

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

moe333 - what a way to have to run a business - one that puts responsibilty on the geotech if something goes seriously wrong due to changed conditions on site . . .

(in court after a groundwater issue forces a $5million lawsuit:
?: "Did you install a standpipe or other groundwater monitoring device?"
Ans: "No."
?: "Why not?";
Ans: "Too expensive and he client wouldn't pay."
?: "Did you put this is writing that the groundwater level could not be determined due to constraints put on you by the client?" Ans: "No."
?: "Mmmmmm - hope you have really good insurance.")

 

[moe333]

BigH - unfortunately that is the reality sometimes - I wish it wasn't. Sometimes you have to choose what you can and can't live without. This one may have been a case where you couldn't live without a standpipe?

 

[Mercycity]

The time of investigation means a lot. If it was dry seasom probably the water table had going down. If you could also tell the materials encountred generaly up to the end of borehole could help us to comment. The two factors may tell you a lot if water table is expected or not. Otherwise if you are not sure, be conservative and allow the water table because the contractor may charge a lot if during implimntation of the project it happen to meet water table otherwise i concur with other colligue to get a correct geotechnical report