Geogrid ripped (stone retaining wall)

[Alan CA]

We have a stone retaining wall (groove-and-tongue), that badly failed. We noticed that the geogrid had ripped an cut all along the roll as if it was nicely cut. What can cause this?
The wall is more than 6.5 ft high, along a road. For the wall to fail, it's understood, but for such a geogrid to be ripped?

 

[oldestguy]

Teen age delinquents with a knife?

 

[Alan CA]

No, it was in soil when it happened. It was not exposed

 

[r13]

Does the cut happen at the connection? Can you provide a photo?

 

[Alan CA]

It was ripped in a straight lone along the long direction of the geogrid roll, 1 foot from the edge (a 1 foot wide strip was ripped off and fell with the collapsed wall). I'll put a photo tomorrow when I go to the office.

 

[oldestguy]

Look for some way for machinery to have done the cut, such-as a roller compacting soil inside a retaining wall (foundation). First off find the purpose of the geogrid. Tensile failure unlikely with only one foot of grip.

 

[r13]

Pay attention to where the tear started. I guess there is a inclined/curved slash at the initiating point, but I've no clue how the damage has occurred at the first place.

 

[Alan CA]

I must correct that it's a retaining wall, not a foundation. Apologies for the mistake and thank you for your replies

 

[Jrit]

A picture would be helpful, but most geogrid should be installed with the long edge of the roll perpendicular to the wall face (cut into pieces rather than rolled out along the wall face). Typically, geogrid used for retaining walls has a much higher tensile strength in the long direction of the roll, as opposed to the short direction.

 

[PEinc]

Jrit makes a good point about the orientation of the geogrid. I was called about a failed wall where the geogrid was installed incorrectly with its strong direction parallel to the wall and the weak direction perpendicular to the wall. The grid was too weak and the entire wall failed as the grid ripped.

http://www.PeirceEngineering.com

 

[Alan CA]

Thank you for your reponses. This helped a lot