CMU Block Web Cracking

[Sean_14]

I have a basement foundation wall below grade in an area to be know to have a high water table. The wall is about 15' in length and was starting to bow about 0.5". We removed the top few courses of hollow 12" CMU and noticed that all of the CMU blocking has cracking in the interior webs. No cracking on the exterior parts of the CMU just the interior webs. Does anyone know why this occurs?

 

[jayrod12]

I would say water ingress into the core and then freezing, if that's a possibility for your region. We had something similar but it was the face shells cracking vertically at the middle of the core

 

[Sean_14]

That was my original thought but why is there no cracking present on the face of the CMU?

 

[JAE]

Possibly cracked during your demolition actions.


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[jayrod12]

Again, water intrusion is just a possiblity. But as to why it wouldn't crack the face shell, if the webs cracked first, then the pressure has already found a release. The face shells would then just move as a unit.

 

[GC_Hopi]

The face shell also appear cracked in a few locations. I would explore another section of wall and be careful with the demo. There appears to be damage from demo.

 

[KootK]

That was my original thought but why is there no cracking present on the face of the CMU?

Because pure tension in the webs would be your critical stress prior to fracture releasing the pressure. I'm feeling the frozen water theory.

The only other thing that I can think of is a shear failure under a strange combination of very high shear and relatively low bending. That's hard to phathom given that the wall doesn't even seem to be reinforced.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me:

http://www.eng-tips.com/viewthread.cfm?qid=456235