Temporary shoring - anchored sheet pile walls 2

[avolonnino]

Are tie backs legal under neighboring adjoining building foundations? Is there any code criteria or protocol that control this form of construction ? I.e. a construction variance, etc.

 

[Ron]

First of all, you would have to get the adjacent property owner's permission for any encroachment onto their property.

Next, it is not a good idea to undermine an existing foundation to construct a deadman for the tieback (you have to tie it to something).

Don't even consider using the adjacent building foundation as the anchoring for your tieback.

Make sure you do a complete documented condition survey of the adjacent building prior to placing any sheet piling. Put crack monitors on all existing cracks.

Assuming you are using a vibratory hammer for sheet pile placement, you can significantly damage adjacent buildings from the vibration of insertion and extraction. Plan to monitor vibrations in the soil adjacent to the existing building and place accelerometers on the building so that levels of vibration felt by the building and foundation can be recorded, both for protection of later claims and for stopping the process if vibrations are excessive.

 

[avolonnino]

Thanks Ron,

I have a contractor who says this is "standard practice" in our area.

They are using grout injected tie backs under the adjacent buildings.

I was hoping there was code ASCE, IBC etc. I found some code statements for encroachment on infrastructure beyond the limits of the project's property.

 

[Ron]

It's fundamental real property law that you can't encroach onto another property. It's called trespassing.

Suppose their grout injection raises the building foundation, or displaces a pipe, or raises a floor slab. If I were the owner of the property I'd go after the contractor, after you for allowing it, after the building department for improperly protecting the property (yes, I know they can't generally be sued, but there are special cases that allow it)...etc.

Don't let them do it. The only reason they currently do it is because they have been lucky. Don't let their luck run out on your project.

 

[avolonnino]

Believe me Not under my watch.

 

[PEinc]

Tiebacks installed under adjacent property is done every day. You need to get permission (a temporary underground easement). Sometimes the easment will be given free. Sometimes the contractor will need to make a deal with the adjacent property owner. Sometimes permission is refused and you need to install internal bracing.

http://www.PeirceEngineering.com

 

[hokie66]

Agree with PEinc. Negotiation with the adjoining property owner is required.

 

[BAretired]

I tend to agree with negotiating with the adjacent property owner, but be sure that those negotiations consider the possibility where tiebacks must be replaced with alternative lateral support.

BA

 

[Ron]

Have seen one recently where sheet piling driven 8 feet from existing structure. Caused cracking of masonry walls and floor slab. When extracted, lateral soil movement caused foundation to cantilever, then crack.

All done without permission of adjacent property owner.

 

[avolonnino]

IBC has code mandates regarding lateral support not being removed under adjoining foundations unless a foundation is underpinned to omit lateral translation.

Anchored walls will deflect causing lateral movement of soil either during installation or at rest which has to be addressed.

How is this achieved?

 

[hokie66]

Any construction which extends below the founding depth of an existing adjacent structure risks damage to the existing building. Rock anchors or soil anchors reduce this risk as compared with cantilevered shoring, or in many cases, internally braced shoring. Deep excavations should always be preceded by existing condition surveys, sometimes referred to as dilapidation reporting. The report is used in assessing damage and cost of making whole the adjacent property owner.

"Temporary shoring" is not necessarily removed. The anchors are classified as temporary if they are not required for support of the finished retainment. Sheet piling is often left in place as lost formwork for reinforced concrete retaining structures.

 

[PEinc]

Good points, hokie66. Even properly installed underpinning can cause a structure to settle a bit.

http://www.PeirceEngineering.com