Pile foundation retrofit

[cmrdata]

We are dealing with an existing building with its columns supported by pile caps and prestressed concrete piles.
Could anyone direct me to any resources/articles regarding the strengthening methods of such piles to increase their load bearing (both gravity and seismic) capacities?
Thank you.

 

[oldestguy]

It's like re-inventing the wheel. I'd suggest looking to companies that are in the business of soil strengthening, such as compaction grouting. They usually are very innovative and can supply references. A Google search will bring up several.

 

[GeoPaveTraffic]

Hire a good geotechnical engineer to evaluate the conditions and the amount of increase you need. Sometimes specialty contractors like the ones suggested by Oldestguy are great, sometimes not so much so. In my opinion, better to start with an engineer with no skin in the game and then reach out to the contracting community based on what your engineer recommends.

Mike Lambert

 

[humanengr]

Are you able to enlarge the pile caps and add piles?
Obviously you won't be able to add driven piles, but you may be able to use
Drilled Piers, Auger-Cast, etc.

 

[cmrdata]

Thank you all for the suggestions.
The other issue is the thickness of the existing pile cap. Any idea how feasible it is to thicken the pile cap while all the piles below are already in place?

 

[oldestguy]

There was a failure of piles under a section of a bridge at Green Bay, WI that was repaired by adding caisson type piles next to it and extending beams through the pier for carrying the full load on the new piles. It may still have references in the room of "Engineering Failures". Happened a year or two ago. In this case, any chance of getting under the pile cap with beams to carry the load to the added piles? The beams would go between existing piles. Corrosion in future?

 

[aeoliantexan]

I believe it is fairly common to drill through the pile cap, install micropiles, and connect them to the cap with grout. Try companies that install micropiles.

You need a structural engineer to address the cap question, but I would guess that you could thicken the cap from the top if there is room. Maybe roughen the column and bond the new cap to it.

We once added a third floor to a hospital by analyzing the belled piers on which it was founded, determining that they were conservatively designed and could take additional load, and surveying the building to confirm that the present settlement was small. Sometimes a good geotechnical engineer can pay for himself.