faq's

Q1: What are the long-term considerations of owning a DCP?

A1: Estimated 3-year maintenance cost of owning a DCP:

1. Unit is calibrated by the manufacturer. No further calibration is required.
2. There is a one-year warranty on all parts, provided they are used in the manner prescribed in the User’s Manual.
3. Upper and Lower Rods—The DCP is an impact instrument and its longevity is a function of the number of times it is used, the soil conditions, and the operator’s technique. Lower rods have failed at the weld below the anvil (4218 Models) because of fatigue, but most often
because of abuse.
4. The Upper and Lower Rod on K-100 Models (with a quick connect pin) are more durable and last longer. This model uses stronger stainless steel rods and does not have a welded point at the anvil.
5. When used as recommended, the Kessler DCPs have lasted for years. After 13 years of manufacturing the DCP, we are delighted to report that only a few are no longer in service.

Q2: Is the bearing capacity in the Excel Template Ultimate or Allowable?

The bearing capacity is Ultimate (NO Safety Factor is included).

Q3: What is the equation for bearing capacity?

A3: The relationship between bearing capacity and CBR adopted by the United States Corp of Engineers (USACE) was developed by the Portland Cement Association (PCA).

Bearing Capacity (psi) q = 3.794*CBR0.⁶⁶⁴

Q4: How do I measure density with the DCP?

A4: The DCP may be used to assess the density of fairly uniform material by relating to penetration rate on the same material. In this way, under compacted or “soft spots” can be identified, even though the DCP does not measure density directly.

Q5: Is the Dynamic CBR measured with the DCP the same as the lab CBR (3-day soak test)?

A5: A field DCP measurement results in a field or in situ CBR and will not normally correlate with the laboratory or soaked CBR of the same material. The test is thus intended to evaluate the in situ strength of a material under existing field conditions.

Q6: Is there a training film on how to use the DCP?

A6: For instructions on the use of the DCP,click here.
Also Minnesota DOT has developed a video that demonstrates the use of the DCP to their unique specifications.

Q7: Is there an ASTM Standard test method for the DCP?

A7: Yes, ASTM D-6951-03 covers our DCPs with 8 Kg and 4.6 Kg hammers. Our manual is listed as a reference in this standard. The specifications & test procedure in our manual are the same as the ASTM standard.

Q8: Is there a correlation between our DCP and the "N" value?

A8: There is no correlation between our DCP and the "N" value.

The "N" value is determined from the STP (Standard Penetration Test). That test is widely used for deep foundation work. A drill rig is used to drop a 140 lb hammer driving a split spoon sampler. The N value can then be used to determine the bearing capacity in psf (pounds per square foot).

Because many of the foundation equations used by engineers use the "N" value we have had similar requests for a correlation from the DCP penetration rate to the "N" value. I have surfaced this with the Corps of Engineers (who own the patent for our DCP) and they (Jeb Tingle PhD, P.E. overseer of the DCP technology) has said because they have provided a correlation to psf there is no need to have a correlation to the "N" value. If however someone wants to pay them to do the research to get a correlation from the DCP penetration rate to the "N" value, they would take this project on.

By the way, we sell the Sower's DCP which does have a correlation from the penetration rate to an N value. Developed years ago by George Sowers at Georgia Tech for Piedmont Soils, it is very popular but much more difficult to use than our K100 DCPs. One must auger to the depth to be tested and then drive the point down 2 inches. This process can be repeated to a depth of about 11 feet.