Pile Capacity Assessment - PDA

Theres plenty about this procedure on the internet.

In practiceit can be as crude as this or as sophisticated as this

I have been involved in design and fabricating a unit similar to that shown in the second video for a civil engineering consultant here.

A calibrated blow is what's required. The civil engineer calculated the subsequent blow increments and knew what to measure with each blow.

I've seen it done in the UK and they put tons of weights on top of the pile, leave it for up to a week with measuring devices attached to see if there is any movement,I would think that dropping a weight on the pile has a fair chance of damaging it.

Bazzer

Dropping a big weight is what they do. Sure it buggers the top of the pile but this gets busted off and the bars bent out to engage the pier cap anyway.

A week is a long time to wait for a result. Are you sure about that? You'd need a lot of dummy mass to load up a pier for a static test.

Are you sure you didn't see this?

They only do it to one in a particular area ,If the ground is the same over the whole site thats all they need, also work doesn't stop, they carry on with piling, I've seen a load measuring 10ft square x about 8ft high balanced on top of a pile I don't know what the weight was but these were concrete blocks so had to be some considerable weight.

Bazzer.

That's quite a balancing act!! I'd like to see that being stacked.

Hammer, topple, DOH!!

This FWHA website link will be most useful for you regarding the PDA test procedure:

http://www.fhwa.dot.gov/publications/research/infrastructure/geotechnical/05159/chapter4.cfm

Additionally, here is a link to an US Army Corps of Engineers (USACOE) Engineering Manual (EM 1110-2-2906, Chapter 5) pertaining to PDA testing of driven piles:

http://140.194.76.129/publications/eng-manuals/em1110-2-2906/c-5.pdf

In my experience with this testing method, it is used for analysis during the driving process, i.e. dynamically as the name suggests. A series of sensors are attached to the pile shell and various data is collected as the pile is driven. On the projects that I was involved with, it was used as a means of separating the driving force actually applied to the pile shell from shell wall compression and rebound. The process would permit verification of the presumptive driving criteria, i.e. hammer blows per unit penetration, and suggest any need for modification of that criteria.

The projects that involved the use of this testing method were usually in areas where there were several strata of loose soils with denser strata intermingled in the soil profile. In these cases, it was desirable from an economic standpoint to use the thinnest wall section and the shortest length of pile to satisfy the ultimate capacity requirements. Certainly, if cost were no concern, heavier piles and longer lengths could be used without any finesse to obtain the desired capacities, but that is not typical nor economical.

If you intend to test piling that is already in place with pile caps, there is no alternative to a static load test, which will involve the application of a load large enough to satisfy the criteria for the pile(s) in the cluster. The geotechnical or structural engineer of record on your project should be able to provide the necessary loading criteria and details to permit a contractor to provide a quote for the work.

Great information. thanks Doogleass.

The static load test option may not be feasible as the existing two-storey building's column is seating on the pile cap.

If the pile length can be estimated using geophysical test (ie parallel seismic or borehole radar) and the pile diameter can be physically measured via trial pit. Would it be reasonable to estimate the pile capacity using these pile dimensions in conjunction with the soil data freshly obtain from borehole (used for geophysical test) adjacent to the pile?

Would it be reasonable....?

Of course it is reasonable to conduct a structural audit. Expensive as a first step but reasonable. You will need the services of a licensed geotech engineer and a civil engineer.

Is this building also in Singapore? Have you checked the city records yet?