Interesting Footing retrofitting situation - Extending Existing retaining wall pier foundation under earth

[rb192]

Hello everyone,

We need to increase the footprint of an existing footing under a retaining wall to support additional loads. Access is limited to one side due to 20 feet of retained earth on the other side, which complicates excavation.

We plan to enlarge the footprint on the southern side and sides, as shown in the attached sketches, through underpinning and constructing a new footing below the existing one.

While extending the footing south is feasible, we face challenges extending it sideways because of the 20' retained soil. The loads on the footing are not concentric, creating moments, as we consider the wall part of the column transferring approximately 900 kips of the load, so extending it further south make matters worse.

If you have experience with similar projects or any ideas on how we can effectively address this situation, please share your insights

Thank you!


PLAN

SECTION - PLAN HORIZONTAL



SECTION - PLAN VERTICAL

 

[LittleInch]

Can't actually see how you're going to do that without the wall collapsing.

Could you not extend the existing footings on the accessible sides by doweling in bars?

But suspect the only way is to remove all the surcharge and re-build the foundation.

 

[JAE]

Do you have room for something like this?
(avoids messing with the existing retained earth)

 

[HTURKAK]

Apparently you are planning only to increase the footprint of the pier footing and IMO , it is not good idea . I would consider the following two options before increasing the footing sizes ,

- The use of tieback anchor block for each pier . If slit trenching and installation of anchor tendons is possible ,
- Or preloaded anchors (e.g dywidag threadbar or similar )

My opinion

 

[PEinc]

There may be more to this problem than was indicated. How does the wall retain 20 feet of soil with only the small wall footing shown in Section 2-2? How many column footings need to be made larger? What is the column spacing?