You can buy a vane unit from a geotechnical supplier as you are pondering.
Yes, sometimes they can only reach to 5 or 10 feet in depth.
Sometimes the soft clay is located at 20 feet in depth which renders your equipment null and void.
Bear in min the cost comes out of your pocket and you may...
When I run an investigation with continuous SPT tests we always advance the casing before the next test is conducted.
High water table in this area of Canada with interbedded silts/sands/sandy silts etc.
The strecher would not work.
The 24 inch SPT sampler works best I have found.
Yes, we most...
Promken,
Like EirChch mentioned: Look for some kind of hydrostatic Pp response line in the sand or sand layers. Draw a straight line (best fit est)
through all the Pp data in the sand and where it roughly crosses the "Zero" mark would equal the water table. If all the Pp data is very low to...
I agree that 50 and 150 kPa are way too big of difference.
What Nkt value did you use to convert the CPT data to shear strengths? 12 - 14 is common.
The most common Su method involves qt, overburden stress and an Nkt value....did you use that formula?
Did the CPT test show a positive pore...
MKIX
Those are great examples and ideas.
Thanks for posting those links.
A chain driven pulley for lifting and large elastics to accelerate the drop
weight so that it impacts with greater energy.
Very KISS
btrueblood
Yes we are considering the lever arm pendulum design as our most likely option.
The anvil and striker on the pendulum would be sizable so I am not worried about spalling over time and related changes in mass.
Yes, we will make the sealed box with a bolted cover so that we can check...
Thanks everyone for guidance and comments.
Please provide additional comments or thoughts if you can see an alternate idea.
We are really trying to keep it KISS.
hydtools: Yes, I am looking at rock breaker type hammer. They tend to have very fast and hard impacts which is good, but they are...
I am a Geotech Engineer and have become invloved in the design of a hammer impact unit.
We need to build a mechnanical device that will push a rod horizonatlly and hit a
plate horizontally. The striker rod will be activated by a switch and upon activation it will shoot out and strike an anvil...
Talk and coordinate with the GPR operator.
Different GPR antenae can produce different results.
Again, maybe the GPR operator can help in this matter.
Maybe do one quick borehole next to a GPR
alignment in order to calibrate your GPR results.
I quickly tried several different antenae a few...
In the past we had to sample a near surface, very hard clay/silty clay/sandy clay (Su = +400 kPa) at a semi remote location.
On our first attempt we crushed and folded all the shelby tubes.
Then we lost the use of the drill rig so we ended up at the position you are at.
Our second attempt using...
As stated previously, check Dr Mayne's website.
He has some interesting research and informative power point files.
Also check Dr Campanella's web site at Univ of British Columbia.
Many of his CPT related research papers can be downloaded from his home page and web site.
Do a search on Jim...
BigH
That is some great production!
Good value for your site investigation buck.
I doubt any of the drillers that I work with could match that speed.
Of course, the soils we typically deal with are soft and saturated so the solid stem auger borehole would not stay open all the way to the bottom...
I am not sure if a CPT contractor is available in your area?
What about the use of solid stem auger drilling for bulk sampling?
In our area of the west coast almost all of the consultants conduct solid stem augers sampling for bulk samples inconjunction with CPT testing to determine the...
Hank,
When your cone meets refusal and you conduct a drill out are you using casing?
Are you just drilling down with a drill out tool? You will have many problems with cone rods breaking if you are pushing the cone through drilled out soil that is has been disturbed.
On past barge CPT...
In the past we have conducted numerous Nilcon vane borings adjacent to CPT tests in order to determine the site specfic Nkt factor. Some of the tests in very soft, sensitive soils showed an Nkt of 11. Other tests in soft to firm clays showed Nkt values in the 11.5 to 13 range. Recent tests in...
Yes, the pictures show an older "Dutch Cone" or "Mechanical Cone".
These tools were used for soils investigations before the introduction of the electronic cone.
The gauges were used for measuring how much pressure was required to seperately push the tip unit and the friction sleeve into the...
I have seen this issue a few times.
Yes, the sonic drill will disturb the soils at least 1 to 1.5 feet ahead of the casing. A downhole hammer drill will also disturb the soils at least 1 foot ahead of the bit.
Your 30 - 40 blows/ft in sonically disturbed soils might actually be closer to a...
Another approach would be to do CPT testing in conjunction with solid stem auger 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...
Mercycity had many very good points.
Consult a local Geotech Eng. (if one is available?)
The local consultant might have some idea if the soils are poor, acceptable of unknown for a house in your area.
Asking your neighbour about his/her house will also give you an idea if you are on a peat bog...
Paul,
The NCHRP Synthesis 368 guide that was issued in 2007 listed a method for correlating the Vs and qt values from a CPTU test. (for clay like soils)
The formula:
Vs (m/sec) = 175(qt)exp 0.627 (qt in kPa)
To convert your qt values to Su we commonly use the this formula:
Su (kPa) = (qt...
