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Re: Tank settlement

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Bhavin,

As Paul suggested, this may be an application for a flexible connection.  For small deflections, this could ve as simple as 2 Dresser-type couplings separated by a short length of pipe.  For your case of 200 mm, I think that you need a specialized product specifically designed to allow for settlement.  One product that I am familiar with is Flex-Tend by Ebaa Iron (http://www.ebaa.com/Products/Flex-Tend/index.htm ).  Be warned, these are not cheap, but they do work.  They have models for 30" pipe that have settlement capacities from 430 mm  to 840 mm.  These will also allow axial expansion and contraction along the pipe axis.

For the record, I have no stake in Ebaa Iron, or any of its subsidiaries, associates, or representatives.

--Kipp Martin
  Carollo Engineers
  Portland, Oregin




>>> "Bhavin Shah" <bhavin.design(--nospam--at)gmail.com> 9/26/2008 9:28 AM >>>
Thanks for the reply.

Can you give any reference for the flexible pipe coupling for 200mm of
the differential settlement ?

Thanks
Bhavin

On 9/24/08, Paul Blomberg <paul.blomberg(--nospam--at)gmail.com> wrote:
>
> 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
> >
>

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