Geotechnical guidelines

The Energy Pipelines CRC engages in a wide range of projects from (for example) sophisticated computational fluid dynamics investigating transient flow phenomena through to preparation of simple practical guidelines.  Two guidelines on geotechnical aspects of pipeline design and operation have recently been released:

  • Vibratory compaction over existing pipelines
  • Buoyancy control by backfill alone

If your company is a member of the APIA Research and Standards Committee (RSC) then you can download these reports from the EPCRC website [1].  You’ll need to contact your RSC representative for the login details.

These two topics may be slightly esoteric to many, but for those who need them the guideline documents should help resolve the substantial uncertainty that has surrounded these subjects for a long time.  There is no new research here, just guideline information from geotechnical specialists for the assistance of pipeline engineers who don’t have a strong geotechnical background.

From the summary of the vibratory compaction report:

Information on compaction loads on pipelines has not been readily available to pipeline engineers. Previous approaches tended to be extremely conservative and may in fact have lead to exposure to other risks (e.g. during construction of protective measures).

Better understanding of loads applied to existing pipelines by construction processes means that appropriate protection can be provided, if it is necessary at all. It is expected that this improved understanding will lead to reduced risk of pipe damage, lower costs to the pipeline owners and better relationships with third parties who need to do work above existing pipelines.

The purpose of this report was to investigate the effects of compaction of soils overlying ground containing buried pipelines, and provide guidance to industry on incorporating these effects into the current methods for assessing stresses in pipelines from external loads using API RP1102.

A literature review of published research into the effect of compaction on earth pressures has been carried out. Methods for assessing vertical and horizontal pressures from compaction loading are outlined, but they do not provide immediate solution for assessing stresses in the pipe in the way API RP 1102 is set out.

A calculation procedure adopting the method in API RP 1102, by converting the compaction loading to an equivalent highway traffic loading, is proposed. The method is applicable for both static and vibratory compaction plant.  …

And from the summary of the buoyancy control report:

Methods for calculating restraint of pipelines against buoyancy forces have not been readily available to pipeline engineers.

A readily available method of determining whether buoyancy control is needed will allow better optimisation of the design of pipelines subject to inundation, and hence lower construction costs (by avoiding buoyancy control measures where they are unnecessary) and/or improved pipeline safety (by providing buoyancy control where it really is necessary).

The purposes of this report were to discuss the effect of buoyancy on buried pipelines and provide guidance to industry on the depth of cover to buried pipelines to resist buoyancy. A literature review of published research and guidance on designing pipelines to resist buoyancy forces has been carried out and is discussed.

This report discusses the principles of buoyancy and its effect on buried pipelines. A method for checking the minimum depth of cover to pipeline to resist the buoyancy force is presented, with suggested parameters for design.  …

[1]  The EPCRC project management website is still being developed and navigation isn’t yet wholly intuitive.  Once you’ve logged in, go to the Project Management tab, select Projects, scroll down the resulting page until you find (10-02) Geotechnical Guidelines and click the arrow at left.  The reports can be downloaded from the bottom of the resulting page.

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