Architecture/Technical Issue- Piling Construction
Introduction to the Issue - Piling
Project consists of Bored Piles with percussion methods. Number of piles is around 800. Type of Contract is Measure and Pay. Piling was designed by the Contractor and design tip levels were proposed based on the available bore holes tests.
Meanwhile there was a design requirement of socketing piles to a minimum depth of 1.5m as per the specification given by the Engineer.
I already realized that previously proposed design tip levels could be changed in line with the actual rock levels found and the requirement of 1.5m socketing depth. For an example, even though the Contractor had proposed a design tip level of (-10.00) based on the predicted rock level at (-8.50) during the design stage; the actual tip level should be (-11.00) if the actual rock was found at (-9.50) instead of originally predicted rock level of (-8.50)
(1) Therefore, my issue is not the design level changes due to the changes in rock level in actual situation. My question is whether it is possible to precisely terminate the boring at the required level? Referring to the above example, is it practical to exactly stop at (-11.00) level. Otherwise, can we consider any tolerance level at the tip level and thereby to terminate the pile boring at (-11.10 or -11.20) instead of exactly at (-11.00) level.
(2) Above question was related to the Pile Boring with Percussion methods. So, how is it differed (the above answer) in considering the Pile Boring with Rotary type and
(3) Driven Pile
I am really interesting to have your answers on this
Thanking You Very Much
First off, I want to be clear, I am not a geotechnical or structural engineer. I can only speak from experience. I have been a Construction Administrator on both driven steel piles and auger cast concrete pile buildings. There is no way you can terminate either based upon a prescribed number of feet.
The number of feet prescribed by the design engineer is based upon soil samples of test cores done on a few spots around the building footing and slab areas. It would be too expensive to do the number of tests required to understand the underlying soil conditions enough to make precise PREdetermination of length.
Typically a resistance of driven pile during installation is what determines ultimate length. In other words once you hit the pile and it only goes down a X inches in Y number of blows (determined by the site engineer for each project).
Typically it is the condition of the soil that the auger brings up that your site geotechnical engineer or installer will observe and use to determine length.
Hope this helps!