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RE: "Hydrovac" for pier construction

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Because of the degree of disturbance. In comparison to traditional auger boring, the disturbance is more severe in hydrovac method.  Formulas, currently in use are based on field tests conducted by FHWA's research program. In my opinion, the component of side friction in vertical load capacity may be affected by the degree of disturbance.

The effect of underreaming is accounted for in FHWA formula.

One of the statements, I have seen, in construction specification is "water jetting shall not be used to excavate hole within the bottom  xx feet of the bottom of the hole". This may be for minimizing the disturbance at the bottom of the hole.

Rajendran



"Polhemus, Bill" <BPolhemus(--nospam--at)wje.com> wrote:

From: Padmanabhan Rajendran [mailto:rakamaka(--nospam--at)yahoo.com]
Sent: Wednesday, May 24, 2006 7:46 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: "Hydrovac" for pier construction
 
Daryl,

It appears that you have designed hydrovac constructed piers. Do you have any insight in to the formulas for determining vertical and lateral load capacities of such piers. Intuitively, these piers should have lower capacities than traditionally drilled peirs.


 
I donâ??t necessarily accept your premise. In each case, youâ??re boring a hole in the earth, and then filling that hole with concrete.
 
Both methods â??disturbâ?? the surrounding soils. In fact, very often drilling fluids are used in boring holes using an augur. Underreaming also does its share of disturbing the soil.
 
Why do you think that hydrovaccing would give â??lower capacitiesâ?? than boring?


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