Unlike deep excavation, trenchless techniques such as microtunnelling bypass surface obstructions and have minimal impact on the surrounding environment. In the case of water and sewer pipeline installations, this has multiple benefits for the community and environment, and reduces risks during installation.
Benefiting the community
The impact of construction on the community is a key consideration when a pipeline installation method is chosen. Microtunnelling has become a popular choice as it causes minimal disruption, resulting in fewer community objections and making it more likely that projects can start without issue.
Traditional installation methods that involve large trenches can disrupt the everyday lives of community members. Microtunnelling only requires an entry and exit pit to be excavated, saving time during construction and rehabilitation, and drastically reducing disruption to the community.
Equipment like the Vermeer AXIS guided boring system also has the benefit of a modular design, which means it can be configured in a number of ways for jobsite footprint and transport considerations to accommodate customer preference and minimise traffic disturbance.
Additionally, in many circumstances with traditional installation methods, you can’t store excavated materials on site so you would require a truck to move the materials around. This costly and time consuming task is virtually eliminated through microtunnelling.
Reducing risks during installation
When tunnelling in urban areas there is a risk that the ground in the vicinity of the installation will move, which can result in costly structural damage. The AXIS system enables one controlled deep excavation that allows keyhole-like installation of a pipeline. With keyhole installations pipe can be installed through one small incision meaning the surrounding ground is left in harmony and existing infrastructure is left almost untouched.
Minimal disruption is particularly important in high density areas where there is a higher chance of damage to structures or underground infrastructure. Whenever deep excavation is involved there’s a risk the ground pressures will become out of balance, causing the ground to move. This movement can result in damage to existing infrastructure or utilities. With deep excavation, you have to maneuver through the underground infrastructure which increases the risk of damage to these assets.
Reducing ground disturbance
Microtunnelling also mitigates the chance of sinkholes forming in the future, which could cause structural damage or injure someone. Sinkholes are not uncommon, and in instances where sinkholes occur, it’s the result of a pipeline being installed – possibly incorrectly – and the ground being disturbed around it.
Sinkholes are most common where there is a leaking water pipe installation. The water finds its way into the ground, the ground moves in with it and you end up with a big void.
By microtunnelling, two things are happening, not every layer of ground is getting disturbed and only the minimum amount is getting cored out. That means the rest of the ground remains unaltered, drastically reducing the risk of sinkholes forming.
The reciprocal advantage
Another advantage of using microtunnelling to install water and sewer pipelines is the use of jacking pipe. Compared to standard pipe, jacking pipe is better to use as it is less likely to have the same joint issues that open cast pipes have. The reason being, if you excavate into the ground to lay a new pipe, you make a new bed and then you have to put the material around the pipe to ensure it won’t move.
You’re then trying to layer up and compact, and rebuild the surface. Because everything has essentially be interfered with there will be a settling period where things will move. As they move, there is the potential that everything will become structurally less sound than it originally was.
When you core a pipe through the ground, the ground is still the guide for the pipe but it is left, for the most part, unaltered, meaning the pipe fits snug in the ground with little environmental disruption.
As microtunnelling is becoming more widely used we are starting to see the short-term benefits it provides for water and pipeline installations, and while the longer-term benefits of microtunnelling will be seen over time, we are certainly finding the results to be positive.