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RE: Drilled piers vs piles

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Title: RE: Drilled piers vs piles

Let me give you all just one perspective on this topic. The following is from a State of the Art report on geotechnical engineering issues for residential and light commercial foundation design and construction, approved last year by the Foundation Performance Association in Houston:

 

Void Boxes. About 38% of [geotechnical reports in the past five years] specified the required void box size under the grade beams. Void boxes are recommended by many geotechnical firms in Houston as a way of reducing foundation movements. Expansive soils once swelled up can theoretically move into a void space area (void box) without lifting the grade beams. The discussion on whether or not void boxes should be used under grade beams on residential foundations was conducted by the Foundation Performance Association. It is generally believed that void boxes under grade beams provide channels for water to flow underneath the foundation system. Therefore, the use of them are discouraged. This discussion and idea was developed in 1996.

 

As a result, again I say “In the past five years or so the use of Void Boxes has been seen less and less in the Southwest.” IMHO, those who still recommend them aren’t keeping up with the literature.

 

William L. Polhemus, Jr. P.E.

Polhemus Engineering Company

Katy, TX, USA

Phone (281) 492-2251

FAX (281) 492-8203

email bill(--nospam--at)polhemus.cc