Concrete Piling proceedure - re platform fill level

[swazimatt]

I am currently doing a platform design for a piled building and need some clarity.

the piles have concrete pile caps that will be about 1.1m deep. The platform level for the basement (tree sides retained, fourth side open) will be in fill now since i have never worked on a piled site i need some clarity for the piling process.

The platform fill will be made up of about 600mm rockfill and then G6 fill material

My current thinking is that i set the top of platform at the same level as the top of the pile caps, the contractor will then carry out localized excavations of 1.1m deep for the piles and pile caps and do the piling with the rig standing 1.1m above the top of pile. Is this the correct procedure? or does the piling rig need to sit at the same level as the top of the piles (1.1m below top of pile cap)

and will they be able to pile through the rock fill?

 

[BigHarvey]

The thickness of your working Platform will be determined by the weight of the piling rig and the mechanical characteristics of the underlying soil.

The lecel of the Platform might be determined by the phreatic level : for cast in situ piles Under bentonite, the level of the Platform must be at leat 1.5 m above natural groundwater level.

600 mm diameter rockfill is definitely a bad idea from a piling contractor's point of view whichever piling technique is used.

 

[swazimatt]

thanks.

I was a bit concerned about the rock fill as well, that can be changed easily enough, my main concern was that the rig would sit 1.1m above the proposed top of pile, and this is my main question

For those that have worked on sites with piles it may be a no-brainer, but i do not want to instruct a fill level only to have the piling contractor arrive on site and say that we need to drop the fill level by 1.1m so he can work (at the same level as the top of piles)

In this case the fill level is determined by the building levels. The upper floor has to tie in with the street level. There will be enough fill above the water table - in fact i would think the rig could drive onto site as it is now

 

[hokie66]

Why are you deciding this? Why not leave it to the contractor? Oh, right, separate contract for bulk earthworks. If the piling can be done without/before the fill, then that is probably the best way. Then they can form the pile caps and fill between.

 

[BigHarvey]

You did not mention the type and size of pile you are planning. Drilling rigs can prove very heavy and you must have a competent soil underneath the tracks if you don't want to see it overturning.

A low cut-off concrete level will just imply a safety margin on the level of the concrete at the end of the session which means a more important trimming operation. Otherwise ther is no big point in having a cut-off level 2 or 3 meters below GL. Just make sure you protect the holes one way or another (backfill, steel cover...) so that nobody gets injured by falling in the excavation.