Technical – Milling mole method｜Yasuda Engineering Co., Ltd

Technical Information

High-density slurry type pipe jacking method with compatible type for underground obstruction Milling mole method

It’s okay if there are obstruction in front of TBM
Ultimate pipe jacking method equipped with four special functions!

4 Special Function

Exploration
Ground improvement
Cutting
Inducing

Function01

Exploration

Exploring steel obstruction in front of TBM during excavation!

If there is an obstacle in front of the planning rote, the obstruction will be caught and detected from the TBM. The electromagnetic waves are emitted from the transmitter coil equipped in the TBM to expose magnetism (primary magnetic field)　to the steel obstruction.
The magnetic steel obstruction emits an induced current, and magnetism (secondary magnetic field) is formed. This magnetism (secondary magnetic field) is detected by the receiver coil equipped in the TBM to determine the presence or absence of steel obstruction.

Function02

Ground improvement

Ground improvement around the obstruction from inside the TBM!

It takes time to cut obstruction. During that time, the ground around the obstruction will loosen, and ground improvement will be carried out to prevent the occurrence of subsidence of underground utilities and ground surface. The milling mall machine is devised so that chemicals can be injected from inside the TBM in case it is impossible to improve the ground from the ground level.

Function03

Cutting

Cut steel obstruction into pieces and discharge!

The milling mole method consists of three devices which are TBM, special telescopic pipe, and special injection pipe. The TBM is equipped with a dedicated special bit dedicated to cutting obstruction, and has a built-in transmitter coil and receiver coil for obstacle exploration. The cutter bit also supports in-machine replacement. The special telescopic pipe is used when cutting the obstruction, and the TBM is pressed against the obstruction at ultra-low speed to cutting. The special injection pipe will be mounted equipment to improve the ground in front of the TBM and around obstruction.

Function04

Inducing

Induce the TBM to a predetermined position in the shaft!

It is a system that induces the TBM to the position by installing a receiver coil at a predetermined position in the reception shaft. It measures from about 40m before reaching and calculates and displays the azimuth angle of the TBM in real time.

FAQ Frequently asked questions about Milling mole method

There is a pipe jacking method to remove obstructions, but how do you remove them?
Is it possible to remove anything?
Special bits are arranged on the cutting wheel of the TBM, and a special telescopic pipe is used to cut at ultra-low speed.
It is an image of “scrape”.
Of course, in order to scrape, it is necessary to fix the obstruction so that it does not move, so ground improvement is necessary. It can be used not only for steel sheet piles, but also for H-beam and reinforced concrete structures.

I often hear that the cutter spokes of the TBM bite into obstruction and make it to stuck. Isn’t it the milling mole method for such a problem?
It will not get stuck.
This is because there is a forward obstacle exploration system that is also a feature of the milling mole method.
It was impossible to predict unexpected obstacles with conventional pipe jacking methods.
However, with this milling mole method, obstacles (contains in steel products) can be confirmed using electromagnetic waves, so it is possible to deal with them in advance.
In addition, because it is equipped with a special telescopic device, it is possible to “slide back” the TBM a little.

How do you dispose of the cut obstacles?
Since the cut obstacles are in the form of iron powder, they are transported to the ground by vacuum transportation in the same way as normal high-density slurry type pipe jacking method.
After that, we will dispose of soil as industrial waste.

Is the classification a high-density slurry type pipe jacking method?
What is the applicable pipe diameter?
The classification is high-density slurry type pipe jacking method.
The applicable pipe diameter is φ800 mm to φ3000 mm. In-machine injection performed from inside the TBM is available from φ1000 mm or more.
If the ground improvement cannot be performed from the ground level, in-machine injection is required, so a pipe diameter of φ1000 mm or more is required.

Do you think that obstructions in the ground are not always left at right angles?
Certainly I don’t know how the underground obstacles are left, but Since this milling mole method cuts at an ultra-low speed, the phenomenon of “slipping” against obstacles does not occur.

For details, please check the Milling Mall method website.