Loss of Drilling Fluid Circulation 2

[enginerding]

I have been asked to review a boring log to come up with some recommendations on the foundation type. The site is in Florida and the boring shows sand, then sandy clary, then stiff clay, then soft limestone.

The boring log notes loss of drilling fluid in each of the two clay layers. The upper layer of clay has 50% loss of drilling fluid circulation noted and the lower has 100% loss.

Would this make a drilled pier foundation not feasible? i.e. would we loose concrete as well?

 

[civilperson]

Drilled pier or auger cast pier would both work. Use casing with drilled pier and fill with concrete while raising the casing. Similarly, put concrete down the center of the auger while raising the auger. Insert rebar cage after removal of the auger.

 

[motorbiketocrank]

Don't take this the wrong way but you really shouldn't give recommendations on the foundation type if it's not your area of expertise and if you're not sure of all the considerations involved (both geotechnically & geologically).

I think you'd need a better understanding of exactly what occurred with the drilling & fluid loss to determine what happened. First, I'd question whether they were definitely using a drilling fluid during the soil sampling or whether they only starting fluid use to facilitate the rock coring. Also, it doesn't make sense to me that you'd lose fluid in a clay layer unless you encountered a void (sinkhole) that is forming in the material (in which case you should see rod drops, etc?). It would make sense that you could lose drilling water into the limestone during coring.

Foundation selection and considerations in limestone are difficult. Be careful.

 

[PEinc]

Excellent answer, geobdg. A star for you.

enginerding, search for thread 256-195834. It deals with drilling, limestone, pinnacles, voids, and sink holes - all considerations for this thread.

 

[fattdad]

The problem is you have no faith in the "fugitive" information shown on the boring log. During drilling you have the opportunity to collect samples (permenant data) and make observations (fugitive data). Leaving the driller to document what may become critical information can be misleading.

Just an observation.

f-d

p.s., Any opportunity for drive piling?



¡papá gordo ain’t no madre flaca!

 

[thewellguy]

The question that you are asking depends on the driller that did the hole. The first thought that comes to mind is what was he using for "fluid." If he was using mud then that kind of fluid loss seems odd. I guess I would spend some more time investigating the logs and possibly do a new boring to varify the info before moving to the next step.