Typical drilling production rate, continuous sampling
Typical drilling production rate, continuous sampling
(OP)
I'm trying to negotiate a contract for a drilling job that has continuous sampling for a depth of 20'. Just curious if anyone out there has a rule of thumb for continuous sampling. I typically use 5' spacing, and I don't have a great feel for how much continuous will slow down the process.
The borings will be drilled through med to stiff clay soils.
Thank you much!
The borings will be drilled through med to stiff clay soils.
Thank you much!





RE: Typical drilling production rate, continuous sampling
Using solid stem augers, our drillers would do a hole like this in about 1 to 1.5 hours in the Toronto area till plains. Set-up and moving time extra. If you are using thin-walled tubes instead of split spoons, you probably should add on an hour or so for handling and waxing - and you would have a hard time pushing into a stiff clay.
RE: Typical drilling production rate, continuous sampling
RE: Typical drilling production rate, continuous sampling
I will assume you are not using the CME Continuous Sampling system with hollow stem augers. The quality and anticipated use of the samples will open and close your options.
For good quality samples, assuming the soil conditions allow, I have sampled with:
1) 1st a Shelby Tube (12"+ as possible) followed with a SPT (24"), cleaned with auger to near bottom of SPT, followed by the Shelby Tube & SPT combination, to total depth. The SPT will fit in the Shelby Hole with minimal sample disturbance. The Shelby which follows the SPT will include the soil disturbance in front of the SPT and should continue into relatively undisturbed soils.
For good to atrocious quality samples, assuming the soil conditions allow, I have sampled with:
1) 1st a Dames & Moore Spoon(24") followed with a California Spoon (24"), followed with a SPT (24"), cleaned with auger to near bottom of SPT, and repeat until the driller's arm falls off.
RE: Typical drilling production rate, continuous sampling
RE: Typical drilling production rate, continuous sampling
Ron - with good drillers and a per foot rate! Let's see - 1-1/2h per hole for 20 at 8hr/day = 5.3 holes/day x 20ft/hole, say 5 holes = 100 ft/day!
RE: Typical drilling production rate, continuous sampling
This approach would give you complete soil profile, a complete SPT profile and a pretty good estimate of the soil shear strengths.
The CPT/auger sampling approach will cost more on a daily basis but you should be able to get 180 feet of production in single working day. After you have looked at the CPT data you could go back and get a piston tube or vane test at any critical zones.
Using the CPT approach will negate any hammer/energy and borehole correction factors.
Of course, the availabilty of CPT contractor might be a cost issue. I guess it also depends on if you prefer analyzing CPT data or lab testing data.
RE: Typical drilling production rate, continuous sampling
RE: Typical drilling production rate, continuous sampling
For Geotech borings, you can take undisturbed samples alternated with spt samples for few borings and if you feel comfortable that you determined your parameters with the undisturbed sample testing and once you have your engineering properties you could correlate with SPT (if clay is consistent through site and you know where G.W. is through site)
For Environmental the most important thing would be avoiding cross contamination... The contractor must have couple of spoons for SPT and decontaminate them in between testing. Or you could use a macro core for testing also.