Pile Design Using Dynamic Probes
Pile Design Using Dynamic Probes
(OP)
We have been asked by a contractor to design a precast concrete pile (450KN safe working load) However the only information available are dynamic probes. 10 probes were carried out and the N100 values plotted. The average depth is 9 metres for the 25blows/100mm values. The hammer weight is 50Kg, drop height 500mm, Cone diameter 45mm, cone type DCP.
Is there a way of relating these values to SPT's or designing the piles directly from the dynamic probes?. I have asked for a proper geotechnical investigation to be carried out but unfortunately the client is adamant he won't pay for it. I've been told the soil is mainly peat overlaying a bounder clay but as no investigation has been carried out we can't be sure.
Is there a way of relating these values to SPT's or designing the piles directly from the dynamic probes?. I have asked for a proper geotechnical investigation to be carried out but unfortunately the client is adamant he won't pay for it. I've been told the soil is mainly peat overlaying a bounder clay but as no investigation has been carried out we can't be sure.





RE: Pile Design Using Dynamic Probes
I'd suggest walking away. If they client won't pay for a proper geotech investigation what else won't they pay for?
RE: Pile Design Using Dynamic Probes
We option use dynamic probing for establishing pile depth, but I always back it up with one or two boreholes. The boreholes enable me to inspect recovered samples and I can compare SPT to dynamic probe results. I have found that they are usually not too far off the mark of each other. Try get your client to do at least one borehole, next to one of your probing locations, then you can compare SPT/DP results and possibly adjust them. You must establish the peat depth/thickness - depending on the peat type, it could be influencing your probe results quite a bit.
I think they were some German codes of practice (DINS) that enabled one to convert dynamic probing to equivalent SPT values.
Just one more thing, should you decide to continue with this project, warn the client of the problems and what your thoughts are, and most importantly get it minuted in writing! Could prove valuable to you one day.
Hope this helps.
RE: Pile Design Using Dynamic Probes
RE: Pile Design Using Dynamic Probes
I will outline potention problems with site to client and provide set calculations for piles and insisty that all piles are tested.
Kieran
RE: Pile Design Using Dynamic Probes