DCP to Allowable Bearing Pressure
DCP to Allowable Bearing Pressure
(OP)
Im new to this forum so excuse my question if someone has asked the same.
I understand DCP results undertaken for a simple building structure for example a 3 storey RC building can be deduced to obtain Allowable Bearing Capacity (kPa). Can someone tell me exactly how this can be obtained. What formulars exactly would i Use? eg. How do i calculate the modulus or compressibility of the material tested at subgrade?
I understand DCP results undertaken for a simple building structure for example a 3 storey RC building can be deduced to obtain Allowable Bearing Capacity (kPa). Can someone tell me exactly how this can be obtained. What formulars exactly would i Use? eg. How do i calculate the modulus or compressibility of the material tested at subgrade?





RE: DCP to Allowable Bearing Pressure
Depending on the technician and the soil conditions, you may only get as much as 3 to 5 feet below grade with a DCP. Your "simple" 3 storing buildings will likely tranfer loads much deeper than that below the bottom of the footing. In my opnion, DCP's should only be used to confirm that conditions are similar to your initial exploration.
I believe there is an ASTM circular (not an ASTM Standard) that correlates DCP blow counts to SPT blow counts, but this should be used with caution. I've found that different regions (geologic conditions) require different charts to provide comparisons.
RE: DCP to Allowable Bearing Pressure
RE: DCP to Allowable Bearing Pressure
RE: DCP to Allowable Bearing Pressure
The DCP i was talking about weighs 9kg (Australian std) and does require abit of muscle and patience to operate! To thank you all, i would like to share with you how a "careful" and "indirect" approach to converting DCP to Allowable Bearing pressure(ABC) can be attained. This is what ive used over the last 4 years.
Steps as follows:
1) Get DCP readings from site to below founding level
2) Present them in 300mm increments
3) Correlate DCP readings to SPT values by using acceptable standards. The Australian code has this correlation. NZ also does have it.
4) Guess a pad or strip footing width to be used.(i always use 1m and work backwards during design stage)
5) Use "Peck & Hanson & Thornburn, 1974" chart and
6) Presto you have an allowable bearing pressure!!
Conditions of use:
- DCP experience and feel for material required
- Know your codes well
- Apply to shallow foundations only
- Always remember ABC is different for different widths!!
- ABC is not the same as Ult bearing pressure
- have the muscles to do the DCP will help!!
- Note, Strip footings can produce greater settelment for the same width and applied pressure hence ABC should be reduced by 20% for strip foundations.
A spreadsheet over the years of DCP vs ABC for different materials is always helpful!
RE: DCP to Allowable Bearing Pressure
There are recurrent disputes over the use of such tools, but I tend to agree with garretk, it's only to be used as a qualitative tool, its ureliability is strong, and the dataset is very much subject to outliers from rods-to-hole friction.
To be used only when necessary, in otherwise unaccessible areas, and so on, or to give a qualitative estimate of soil strenght only at shallow depths...
RE: DCP to Allowable Bearing Pressure
With a 20 mm diameter probe (which is standard in some areas), I suspect that any coarse gravel will affect the result.
This probably falls into the same subject as using a pocket penetrometer to measure unconfined compressive strength. Much can affect it. However as a rough tool it works, when you consider what affects it.
RE: DCP to Allowable Bearing Pressure
RE: DCP to Allowable Bearing Pressure
Follow this link to find the document abstract: http://ww
Again, as stated above, I've never based calculations around this alone. Always just infilling data spots between the more empirical insitu testing methods.
Regards
Soiledup
RE: DCP to Allowable Bearing Pressure
It sounds like you are referring ot the US Army Corps of Engineers DCP. The FHWA and many state DOTs have numerous studies on this device. It is used almost exclusively for pavement design applications.