microtunnelling

Time and costs pressures are at the forefront of the minds of project managers, playing a key role when deciding the method of construction, and the contractor and materials selected. However, when something goes wrong delays can occur, causing time and cost blowouts. Here, Stuart Harrison, Managing Director at Edge Underground, looks at some of the common causes of delays on pipeline installation projects and how to avoid them.

Mr Harrison the biggest causes of delays are poor planning and lacking the right information from the start of the project.

“In the past, I have been contracted to complete numerous jobs that were passed onto me from previous contractors and asked to get them done within a fraction of the time. The pattern I’ve noticed is that a lack of information will get contractors into trouble,” Mr Harrison said.

“Having all the information about the prevailing ground conditions at a site, pre-planning for any possible problems, and using the right equipment can all prevent blowouts from occurring.”

Different ground conditions  

While contractors should always be provided the geotechnical survey information about the site, these only provide part of the picture or may not be correct at all. If the contractor doesn’t have the correct details there is a higher chance of the wrong equipment being used, which can result in costly blowouts.

“I was called in on one project where the geotech survey indicated the ground was sandy clay. The problem was, when drilling started, it was discovered it was actually wet sand with clay bits, and because they were using a vacuum style machine with wet ground, the head kept dropping.

“The result was the contractor was unable to complete installation after four weeks and two attempted jacks that only reached around 10m before having to be aborted. This delay, although no fault of the contractor, cost time and money.

“Edge Underground was called in and was able to do a 94m pilot shaft in three days. Using the Vermeer AXIS laser guided boring machine, we were able to complete a pilot line, check the conditions and upon confirming ground conditions, we were able to select the correct drill head and advise the client of the best pipe materials to suit those conditions.”

The importance of pre-planning

If you’ve got a project with a very strict time limit, if you don’t select a contractor with the experience to plan for different scenarios, there is a much greater chance of something going wrong, and time and cost blowouts occuring.

“Edge Underground worked on a gravity sewer installation underneath a railway that needed to be completed in 48 hours. Because of this, planning and organisation of the construction had to be highly effective and closely monitored.

“The project required a high level of organisation, with the most appropriate crews, tools, materials and drilling equipment needed from the very start of the installation. Contingency plans for changing ground conditions, disposal of drilling mud, mechanical failure and supply of materials all had to be prepared before the works could begin.”

These were vital to ensure the project was executed quickly and smoothly, with a clear action plan and backup if something were to go wrong.

“That’s not to say that all projects need this level of pre-planning, but an experienced contractor is able to identify what possible issues could come up on a site and plan for them according to project requirements,” Mr Harrison said.

Versatile equipment

The main problem facing contractors is that most microtunnelling systems lack the versatility to work through a wide range of ground conditions, or to offer a variety of pipes and configurations. This limits the amount of pre-planning they can do, as adaptations are hard to make once a job has started.

“The Vermeer AXIS has been designed to provide contractors with a versatile system that combines high efficiency, productivity and pinpoint precision, allowing contractors to complete microtunnelling jobs with minimal risk, while saving time and money.

“Unlike traditional pilot microtunnelling systems which displace the ground, the Vermeer AXIS installs pilot lines via a vacuum extraction method. This method cuts and extracts the ground as it moves, which eliminates the risk of surrounding assets being affected by the displacement of the ground.

“This also allows contractors to visually inspect the condition of the earth that is being excavated at the face, so they can then adapt the tooling to best suit conditions.” 

Furthermore, taditional slurry microtunnelling techniques rely on the jacking of a product pipe to propel the microtunnel head, but when the ground substantially changes mid-installation, inevitability there will be a need to dig up the head.

“The Vermeer AXIS eliminates this problem as it allows contractors to complete a 345mm pilot line before upsizing and jacking. It also gives contractors the ability to retract, access and change the machine head part way through drilling the pilot line. Contractors are able to configure the cutting tool to test for changing conditions before committing to jacking the final line,” Mr Harrison said.

“There are a lot of microtunnelling contractors out there with fantastic capabilities and machines, but without knowing the exact ground conditions onsite, pre-planning or versatile equipment, even the best contractor can be caught by surprise, resulting in cost and time blowouts.”

This partner content is brought to you by Edge Underground. For more information, visit edgeunderground.co.

Lauren brings a fresh approach to content. While she’s previously written for publications as diverse as Australian Geographic, The Border Watch and Girlfriend, she’s found her true passion in her current role as an editor in the world of energy and infrastructure trade magazines.

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