Microtunnelling technology has come a long way since it was first developed, and can now provide projects with significant cost savings. Here, we look at three key areas where microtunneling can help projects save time and money.
Stuart Harrison, Managing Director at Edge Underground, said that while open-cut methods have traditionally been more cost effective, microtunnelling now offers a competitive alternative with several features helping contractors keep the cost of installation to a minimum.
“Having the correct equipment, such as the Vermeer AXIS laser guided boring machine, can greatly reduce project costs as it has been designed to maximise productivity and reduce risk.”
No structural pits
One of the ways that the Vermeer AXIS system helps reduce project costs is that it does not require structural pits in areas where the ground conditions are relatively stable.
Mr Harrison said this was possible due to the carefully designed drill head along with the use of the vacuum excavation method that allows it to core a pilot hole through the ground, and leave a dry and stable pilot hole where the pipe is then installed.
“Because the pilot hole is kept dry, there is no ground swelling which is typical in areas where there are certain clay style conditions,” Mr Harrison said.
“Unlike other microtunnelling systems, the Vermeer AXIS system only requires a low amount of thrust and pullback force to create a bore when ground conditions are stable, so a structural backstop or shaft constructed in the launch pit is not needed. This reduces costs and saves time as there is minimal machine preparation.”
A defining feature of the AXIS system is it has the ability to retract, allowing contractors to perform a pilot line through the ground and retract the drill head if any problems are encountered.
“Retracting allows contractors to inspect the ground and change the drill head to one that best suits the prevailing ground conditions,” Mr Harrison said.
“This increases the chance of a successful installation and keeps costs down as not only are the ground conditions known, but in the case of changing conditions, the drill head doesn’t need to be dug out from above which can make project costs quickly increase.”
Minimal restoration costs
Microtunnelling also reduces project costs as there is minimal restoration required when compared to open-cut methods.
“Unlike open-cut methods which require excavation along the length of the pipeline route, microtunnelling only needs two excavation pits that can serve as manhole locations. This saves additional excavation time and resources, and greatly reduces restoration costs,” Mr Harrison said.
“These cost savings increase the deeper the pipeline needs to be installed. Compared to open-cut installations, the cost of microtunnelling changes minimally with depth, making it more cost-effective after a certain point of depth. There are a number of factors that influence what this point of depth is, including ground conditions, job location and other obstructions. For example in an urban environment in a road reserve area, it can be 2m deep, while in a greenfield environment, this could increase to 5m plus.”
A cost-effective alternative
Mr Harrison said these are only three of the main areas where microtunnelling is proving to be more cost-effective than open-cut methods.
“If we are to look at other areas, open-cut is quickly becoming more expensive due to rising indirect costs of fuel, spoil waste disposal, and environmental and social impacts.
“To put this in perspective, the Louisiana Technical Institute has used bid data to estimate that a total overall saving of up to 75 per cent can be realised on projects where microtunnelling is used.”