Cracking the Case: A Geoforensic Investigation into a Building Failure

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 Building Failure 

My Geotechnical Firm performed a Geoforensic investigation of a recently built building. 

The building, constructed in 2015, began developing cracks in its walls and floor slabs by 2017.









Their investigation found that the slab had heaved.

Through a series of Geoforensic tests, they determined that the building had improper select fill that was backfilled under the foundation slab. The Plastic Index (PI) of this backfilled fill was between 25 and 29.  

The Structural Select backfill should be no more than a PI of 20.

A little water under the slab, and it will react with this highly expansive soil and induce the heaving that you see.

Another investigation revealed that they had the building had negative drainage.




They also noticed that the planting vegetation was too close to the building. Their landscape irrigation system was also too close to the building. Area drains were higher than the grade which created ponding in the area during a rainfall.





They also determined that the select backfill was placed at a depth of 5’ under the foundation slab. In their review, this area had a PVR (Potential Vertical Rise) of 3.6”. Their calculations concluded that to achieve a PVR of 1” or less, which is sufficient for this building, they would have had to place 8’ of backfill under the slab.

Reviewing these deficiencies;

1)     High PI (25-29) soil used as backfill under the foundation slab.

2)    The insufficient depth of the select backfill was only 5’. This depth should have been 8” to reduce the PVR to 1”.

3)    Inadequate drainage around the building leads to water mitigation under the building and induces the heaving of the highly expansive soil.

 To eliminate these failures on your next building project, ensure that your Construction Manager or General Contractor has a QC (Quality Control) program and that they adhere to it.

I wish you success on your project.

Shettig Construction Management provides Professional Construction Management services from the inception of your project through completion. www.shettig.com

mshettig@gmail.com








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