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RE: Tank settlement

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I agree with Paul.  I too have used a flex connection.

 

Another option is to do a different type of foundation.  You could do a deep foundation system (helical piers, caissons, or driven piles) to significantly reduce settlement, or you could do a soil stabilization effort after the fact.  You could do a urethane foam injection to densify the soil and negate the initial settlements.  I have heard of this procedure working in the past though have never experienced it.  I have heard the success stories (of course).

 

Dave Maynard

Gillette, WY


From: Paul Blomberg [mailto:paul.blomberg(--nospam--at)gmail.com]
Sent: Wednesday, September 24, 2008 11:46 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Tank settlement

 

150 mm (6") is a lot of settlement.  Talk to the Geotechnical Engineer on methods to lower the settlement.  Alternatives include piles and different soil stabilization techniques.  You might also be able to place overburden on the site to allow the soil column to consolidate, then remove the overburden and place the tank.  This technique might take a long time to be effective in clayey soils.

 

Again, the Geotechnical Engineer is the person to talk with.

 

I have used a flex connection on the tank pipes when settlement was expected over the long haul.  That pipe coupling accommodated the differential movement (200mm) without overstressing the pipe.  I don't know if they are available for a 30" diameter pipe.

 

Paul.

Phoenix, AZ. USA

On Wed, Sep 24, 2008 at 10:18 AM, Bhavin Shah <bhavin.design(--nospam--at)gmail.com> wrote:

This is regarding tank (15.0m diameter & 15.0m height) supported on
ring wall (inside of the ring wall has been filled up with the
compacted sand.) resting on clayey soil.

For design of the foundation total settlement at the tank has been
considered as 150mm (immediate settlement =15mm + consolidation
settlement = 135mm) as per the soil report. However, as informed by
Piping engineer, for pipes (30" dia.)connected to the tank,
permissible differential settlement is only 50mm because of the
congested plant and as per the flexibility analysis.

Kindly advice what measures may be taken so that tank foundation can
be designed for 150mm of the settlement.

Thanks
Bhavin