Iseki Poly-Tech MBM wins new machine award
Japanese tunnel boring machine (TBM) manufacturer Iseki Poly-Tech was awarded the New Machine Award for a micro-tunnel boring machine (MTBM) designed with the ability to retract and be redeployed in the same bore.
The advancement, which the company expects will become highly sought-after, could revolutionise the microtunnelling industry.
The new machine, a slurry-type MTBM, was developed by Iseki Poly-Tech as a solution to the problems that come with operating in confined spaces. It’s unique feature is its ability to pull-back and redeploy in the same bore.
During this process, the soil at the face of and around the machine is stabilised and paths of water in-flow can be ‘cut-off’ using chemical grouting.
The geological condition and any unknown obstructions in the tunnel face can be observed via a charged coupled device camera which can be inserted through observation ports.
In addition to this, for extended drives in hard rock or gravel with boulders, using the pull-back mean that the cutter heads can be replaced during the drive.
Iseki Poly-Tech developed the machine after it found that the diameter of the closed-face MTBMs is often so small that it is extremely difficult to continue boring when facing unforeseen obstructions on the intended alignment.
This issue has been solved through the addition of the feature which allows the machine to be pulled back and redeployed easily after the removal of obstructions.
Reducible machine allows pull-back and cutter-head changes
When the MTBM is pulled back, the dimension of the cutting wheel needs to be reduced because the outer diameter of the face is slightly larger than that of the pipe diameter.
To accomplish this, all the cutter bits of the outer periphery are folded inward to reduce the diameter by pulling back the centre-axis rod of the MTBM.
This feature allows the MTBM to arrive at an existing building or pipeline without the need for an arrival shaft as it can be pulled back to the starting shaft after a drive.
The MTBM can be reset into the same bore or can be used for other drives or projects.
When the MTBM is pulled back, the collapse of the tunnel face and the surrounding ground can be prevented through the use of chemical grout which is injected from inside and around the machine, known as the over-cutting area, which aims to stem water inflow and improve the ground.
The chemical grouting, at the face and on the sides of the machine, normally uses silicate based grouts.
When starting the next drive, the outer diameter of the cutting wheel is expanded to the original size by pushing in the centre-axis rod.
The machine has the ability to be deployed on steel pipes, but also on thicker walled reinforced concrete pipes too.
With the design of this machine, Iseki Poly-Tech has anticipated for the future, when conditions are anticipated to become more severe.
It has created a machine that is suitable for a smaller construction space, undetectable obstructions and no possibility for arrival shafts will be increasing.
The development provides an economic solution to meet the modern challenge of underground construction and is expected to be used widely in the not too distant future.
For more information visit the Iseki Poly-Tech website.
This article was featured in the Winter 2017 edition of Trenchless International. To view the magazine on your PC, Mac, tablet, or mobile device, click here.
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