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Building Failure  My Geotechnical Firm performed a Geoforensic investigation of a School in South Texas. Drilled piers were to be built according to the above design. All piers would be constructed at a depth of 13’. They dug investigation holes at several of the piers and found that they were not constructed according to the design. Pier depths were measured at 10’6” instead of the design depth of 13’. The Bell size was constructed at 36” instead of the design of 78”. The Shaft diameter was constructed at 18” instead of the design of 30”. They also found that the fill under the slab was highly expansive with a PI (Plastic Index) of 32-40. In their review of the expansive soil, they determined that the PVR (Potential Vertical Rise) is 3.6”. Therefore, the original design of a 13’ depth was not sufficient to resist the uplift loads due to the expansive soils. The minimum depth should have been a minimum of 25’. They also found negative drainage on the east and west sides of ...

  A concrete crane collapses at the Texas Medical Center project and injures one worker.   My Geotechnical firm investigated the soil conditions under the crane. They found a loose sandy soil that was not compacted. They determined that the soil bearing capacity was 1,000 psf. The actual loading of the crane and the concrete container was 5,000 psf. They also discovered that the outrigger area of the crane was 2.25 SF, and the wood outrigger was also only 2.25 SF. The outrigger base was too small and therefore insufficient. A summary of the collapse. 1)      Insufficient bearing capacity of the soil underneath the crane. 2)     Outrigger pads are too small 3)     Settlement of the soil under the crane. Perform a bearing capacity check by a geotechnical engineer for any crane or concrete pump truck outrigger used on the project. Meet with your crane operator and review a lifting plan before work commences.  ...

  Crane mishap kills one on Dallas School project My Geotechnical firm investigated the crane collapse. They reviewed the soil conditions under the crane and found that the soil had sufficient strength and compaction. However, for your projects, perform a bearing capacity check by a geotechnical engineer for any crane or concrete pump truck outrigger that will be used on the project. Shifting Center of Gravity The geotechnical investigation determined that the crane was overloaded.  The center of gravity is vital in operating a crane. When operating a crane, a crane operator should always ensure that the center of gravity is maintained within the crane’s body to avoid crane overturn. Meet with your crane operator and review a lifting plan before work commences. Consider all the aspects of the lift; 1)      Weight 2)     Center of gravity 3)     Lifting points on the load 4)     The path that the load will ...

  Industrial Building Slab Failure  My Geotechnical Firm performed a Geoforensic investigation of a recently built Industrial building constructed in the Houston area. They investigated the failing interior concrete slab. They documented over 80 cracks from under 10’ to over 40’ in length and from .02” to .06” in width. They core drilled the slab and performed compressive tests. The results weren’t good. Through their laboratory analysis, they determined that  1) Water was added at the project site, which affected the consistency of the mix.  2) An inferior aggregate was used in the mix.  3) The control spacing was measured from 15’ to 25’ and the depth was .25”. ACI recommends that the control joint be ¼ the thickness of the slab. A 7” slab should have a control depth of 1.75”. Control joint spacing should be twice the thickness of the slab in feet. Therefore, for a 7” slab, the maximum joint distance should be 14’. 4) Based on the forklift that was present dur...