Contractors and asset managers alike should ask themselves the question – are they selecting or inheriting the right pipe?
CivilCode Managing Director John Bower can help with the answer.
Along with founding and managing the software development company CivilCode, Mr Bower is also a consulting engineer and the Principal of Independent Civil Solutions.
With extensive experience in the industry, Mr Bower offers expert advice for pipe selection that is second to none.
MDG-S Mr Bower said the recent release of the Microtunnelling Design Guidelines for Sewers (MDG-S) has provided an opportunity to revisit some important design fundamentals.
Plus, with the increasing capability of methods of installation often involving installation of relatively low stiffness pipe, it has become even more important to understand what strength of pipe is required for the permanent design loads.
“Whether it is installing a steel pipe under a major highway or a GRP jacking or sleeve pipe in a microtunnel under a railway line, understanding the minimum required strength or stiffness of pipe is fundamental,” said Mr Bower.
“Over the past few years, I have written a number of papers on this subject, and I was verypleased to have been able to contribute to the MDG-S.”
The MDG-S explains that most pipes can either be classified as rigid (such as concrete or clay) or flexible (such as PE, PVC, steel, GRP and polypropylene).
For rigid pipes, the existing design standard provide equations for calculating the relevant permanent design loads for bores or trenchless installations.
“The only difference between the loads for a conventional (trench or embankment) or a trenchless installation, is how the soil loads are calculated,” said Mr Bower.
However, in recent times, more and more flexible pipes are being installed using microtunnelling, particularly for sewerage installations.
“The relevant design standard for structural design of flexible pipes is AS/NZS 2566.1, although this standard does not provide guidance on bored or jacked installations.
“But, as stated in the MDG-S, the commentary to AS/NZS 2566.1 (Supp. 1) does provide details as to how soil loads can be calculated for “bores”.
“Other loads can then be determined using the other sections of AS/NZS 2566.1.”
Mr Bower said, ultimately, the main differences between a trenchless and a conventional trenched installation are how the soil loads should be calculated, what side support can be expected and how the design equations can and should be applied.
“As explained in the MDG-S, effective grouting of the annulus can be an important part of the design to ensure side support from the native soil can be relied on,” he said.
“Although not included in the MDG-S, it is also possible to carry out a design based on the pipe stiffness alone if the grouting is unlikely to be effective or cannot be completed for some reason.”
FlxPipe Software
“If you are thinking that this all sounds a bit complicated, fortunately CivilCode has made it easy for both designers and contractors alike,” said Mr Bower.
In 2020, CivilCode released a trenchless design option for its FlxPipe design software, being an online application for structural design of buried flexible pipes to AS/NZS 2566.1.
The new trenchless option allows for the design of both new pipe installations and pipeline renovation.
With a company-wide aim to produce civil engineering design software to remove the drudgery of manual calculations while retaining transparency at all stages of the process, CivilCode will guide users every step of the way including training on design theory and using FlxPipe.
For more information visit www.civilcode.com.au
This article was featured in the March 2021 edition of Trenchless Australasia. To view the magazine on your PC, Mac, tablet or mobile device, click here.