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helical anchors

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Hi Michael:


Helical anchors I have used are Dixie.


When installed, one of the parameters is that the contractor achieve a specified torque on the anchor.  If this torque is not achieved, the anchor is installed deeper, or the contractor has the option of using a larger helix, or an extension with a greater number or helices.


The value of the torque is related through testing to the strength of the anchor, both compression and tension. 


If the soil is relatively wet, the torque would be very low, and unacceptable.


For hospital projects we always specify a compression load test on an anchor or a sample anchor.  This would provide additional local assurance of the performance.


This is one of the reasons I like helical anchors.  If loose or wet soil in the particular location of the anchor is experienced, the anchor can be extended through the loose material. 


The soils report is also critical since it will tell you if you have hard layers at the top of the soil which are not adequate to hold the designed load, and which you will want to penetrate.



Bob Freeman, Structural Designer