Temporary Shoring / Wall System To Support Existing Structure

[RFreund]

What type of retention system do you prefer when a proposed wall is being placed in close proximity and supporting an existing structure?
In this case a segmental wall approx 12' tall will be placed about 10' or so from a structure on the high side of the wall. In order to install the wall system the excavation would be with in 4-5 of the structure. I was thinking that the vibration from driving sheet piling or soldier piles may cause movement/damage to the existing structure. Therefore maybe using drilled soldier piles and lagging would be better?

Any thoughts on this situation or any situation in general when you have a tight area and need to support an existing structure above the wall?

Thanks in advance!

EIT

http://www.HowToEngineer.com

 

[dcarr82775]

Where are the footings for the high side building? Are they in the retained zone, or below it?

Also, I would scrap the MSE wall in this scenario. Why build two walls? Just build a single wall to do the trick.

I have done many drilled shaft walls directly adjacent to existing buildings. Sometimes there is vibration monitoring, sometimes not, but I have never had a problem with the drilled shafts.

 

[RFreund]

dcarr thanks for the response. A few responses and more questions:

This situation is a bit different - it is an old 'stone' foundation that is only 24" below grade. The footing is on the border of the active zone but when excavating they would need steeper than a 1:1 slope. The structure only covers a small portion of the entire wall (maybe 40' of a 300' long wall) so the shoring maybe permanent but they still want the segmental facing as it would be used for the rest of the wall.
When you say drilled shaft walls are you referring to something like a secant pile wall? I suppose a soldier pile wall would need to be top down construction in this situation.


EIT

http://www.HowToEngineer.com

 

[dcarr82775]

I wasn't thinking a secant pier wall, just soldier beams installed in drilled shafts backfilled with concrete. You could use a shotcrete facing attached to the soldier beams and the finish face block could be attached to it.

I would also design for at-rest pressures in this area.

 

[PEinc]

I agree with dcarr82775. Why build two walls when you can build one. It sounds like an MSE wall is the wrong wall type. It takes up too much room and comes too close to the adjacent building. The 12' high wall is 10' away from a building that is founded 2' below grade. Therefore, the existing foundation is 8 foot away from the face of wall and about 10 above the bottom of proposed wall. That probably places the existing wall footing beyond the active soil wedge. A conservatively designed, top down, soldier beam retaining wall with a permanent concrete facing would probably be better than an MSE wall with temporary sheeting. At-rest earth pressure is probably overkill that far from the building but I did suggest designing conservatively. Also, it is usually not wise to support a building with sheeting.

http://www.PeirceEngineering.com

 

[RFreund]

I agree that it is out of the active wedge or very close. I also agree with both comments about building 2 walls as opposed to one. However in this situation the wall is about 250' long varying height from nothing to 12-13' tall. The structure is about 30' of wall length. I think that building 2 walls (SRW wall is facing at soilder pill) is still less expensive than building the entire wall as a soildier pile wall no? I don't have much cost estimating expierence but I have seen Soldier pile walls twice as expensive as SRW. Also SRW walls usually run about $25-30/face square ft.

Also is vibration typically a problem in cases like these with driven piles or sheeting? Is it typically monitored?

Thanks again.

EIT

http://www.HowToEngineer.com

 

[PEinc]

You could underpin the 30' long building and then install your MSE wall in an open cut.

http://www.PeirceEngineering.com

 

[RFreund]

How about vibrating in sheeting? Do u think contractors would be willing to do this given the site constraints

EIT

http://www.HowToEngineer.com

 

[PEinc]

Steel sheet piling is a flexible wall system. Flexibility means deflection. Deflection can mean settlement.
Vibration right next to a building can cause settlement and cracking, in addition to being very annoying.
For most projects, buildings should be underpinned if possible, not sheeted.

http://www.PeirceEngineering.com