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Trench Reinstatement - Embedment of Pipe with Screenings

  • 1.  Trench Reinstatement - Embedment of Pipe with Screenings

    Posted 12 May 2019 20:27
    Hi there,

    We're currently undertaking a staged project of stormwater construction using concrete RRJ pipes through a township area with relatively old residential homes. Our first stage has seen some complaints about their homes cracking, allegedly as a result of the works, through both compaction techniques and some minor rock breaking during excavation. This is being sorted out through insurance claims and the like - no issues here.
    What my question is, has anyone used self-compacting screenings to embed pipes such as these? In a previous life I used this method at the Adelaide Desalination Plant for the GRP pipework as specified by SA Water. I have found a Technical Guideline from them detailing that this is an acceptable method with a minimum Density Index of 80%, but can't find any other specifications other than SA10-7 which is a Department of Planning, Transport and Infrastructure (SA once again) specified material. My direct manager thinks I'm talking black magic but is willing to change his view with acceptable evidence and information. Can anyone assist please?

    Kerri Baker
    Wattle Range Council

  • 2.  RE: Trench Reinstatement - Embedment of Pipe with Screenings

    Posted 15 May 2019 18:04
    Dear Kerri and Earl

    I have been involved in several GRP pipe failures and assessments. From results of inspection and investigation (such as the Dong Jiang Pipeline in HKSAR), the material is very flexible, and requires proper embedment and support. It is the most installation sensitive modern pressure pipeline material I am aware of. Surprisingly, the material also undergoes "creep".

    The issue with flexibility manifests itself with leaking joints - excessive deflection.

    However, one of the biggest problems with the material is that it often fails catastrophically - indeed in a brittle manner.

    Accordingly, I would suggest proper embedment, surround and compaction - whilst maintaining circular profile is essential.

    There are some photographs of DongJiang DN2200 main on our website
    and I co-authored an international conference paper with Greg Moore (formerly with SA Water) in early 2000's.

    Hope this helps.

    Philip Ferguson
    Manager PCA


  • 3.  RE: Trench Reinstatement - Embedment of Pipe with Screenings

    Posted 19 May 2019 18:18
    ​Hi Kerri,

    It sounds like flowable fill (mix of water, sand, and a small percentage of cement) may be an option for this project. However, without knowing the details it is hard to say for sure. Flowable fill is not the cheapest option but if it helps avoid messy liability claims then it may be worth the extra costs. Check with your design engineer to see whether this is viable option.  Also check with Boral or the local concrete suppliers to see if they offer flowable fill. Last but not least check with your councils standards guru to see if they will allow this in lieu of the typical bedding. I have provided a link below that does a better job of explaining flowable fill than I possibly could.  Hopefully this information is helpful!

    :: Flowable Fill | Faster, Safer, Economical ::
    Flowablefill remove preview
    :: Flowable Fill | Faster, Safer, Economical ::
    Flowable Fill | Faster, Safer, Economical, Flowable Concrete, Expanding the Concrete Industry Through Promotion, Advocacy, Education, Leadership
    View this on Flowablefill >


    Earl DuPriest

    Asset Management Program Manager

    Charleston Water System

    103 St. Philip Street | Charleston, SC 29403

    Tel: 843-727-7202

    Mob: 843-214-4310