Tunnel boring machines TBM

The expansion of today's transportation infrastructure necessitates the building of extremely lengthy tunnels, which makes tunnel boring machines, or TBMs, more and more important.

Tunnel boring machines TBM



In today's busy times, it is crucial to be able to avoid natural barriers and reduce travel distance, which is made possible by tunnels.

A tunnel boring machine (TBM), commonly referred to as a "mole," is a device used to drill tunnels, mostly in solid rock but also in soil and softer rock. The revolving roller head, whose diameter spans from one metre (micro-TBM) to 19 metres, is the most significant component. Rock fragments are crushed by the knives and cleavers on the skull. Hydraulic cylinders are used to advance the entire machine up against the sidewalls of the tunnel profile. Belts or mud are used to convey the excavated material.

The machine also has a system for drilling and putting anchors, as well as a system for automatically installing substructure components. Their length may reach 200 metres.

geotech tbm


Names of machines that drill tunnels.


The legendary Bertha is in first position because some names have gained greater notoriety than others. Bertha was a 17.5 m diameter tunnel boring machine created especially for the Seattle, Washington, United States, Alaskan Way Viaduct Replacement Tunnel Project. The primary bearing seal system had pieces that were broken when tunnelling started in 2013, which led to the bearing overheating while it was in service. A pit was excavated from the surface for the following two years in order to repair the device. In 2019, the tunnel opened to traffic. Large expenses emerged as a result of the machine's two-year delay, exceeding the budgeted amount.

The Gotthard Base Tunnel, the world's longest rail tunnel, reduces the distance between Milan, Italy, and Zurich, Switzerland, by an hour. The 57-kilometer-long tunnel's last section was broken through using the machine known as Sissi.

England and continental Europe are connected through the well-known Channel Tunnel (France). The underwater portion of this tunnel is the longest in the world at 37.9 kilometres, while the overall tube is 50 kilometres long. Although both English and French workers contributed to the tunnel's construction, the English side completed the bulk of it. All French drilling machines were given feminine names, such as Brigitte, Europa, Catherine, Virginie, Pascaline, and Séverine, as opposed to English equipment, which were given numerical names.

TBM Virginie, tunel Channel

TBM Virginie, tunel Channel


Which method of tunnel construction will be chosen.


The features of the future tunnel, the presence of groundwater, the geological structure, and the availability of machinery all have a role in the type of tunnel construction that is chosen. TBMs are incredibly effective, but they need a substantial upfront investment, and because of their size and complexity, transportation is challenging and occasionally not economical. They are frequently created especially for a given tunnel construction site because of these factors.

The majority of the tunnels in our region are found along motorways. Construction is most frequently done using the flexible, adaptable "New Austrian Tunnel Method" (NATM), which has minimal investment costs.

Due to Croatia's relatively small tunnel sections (up to around 6 km), compared to other nations, it is assumed that tunnel boring equipment are not employed there (eg Norway - approx. 25 km). It's important to consider the high cost of TBMs as well as the shortage of competent staff.


Lighting effects in the longest road tunnel in the world – the Lærdal tunnel.


It is not unexpected that Norwegians create tunnels that not only run through hills and mountains but also connect fjords because their nation is famed for its fjords and high mountains.
The Laerdal Tunnel, measuring an amazing 24.5 kilometres between Aurland and Lrdal on the new major route between Oslo and Bergen, is the longest road tunnel in the world. To avoid creating a road on unsuitable and unstable terrain where there is a great risk of landslides, it was decided to construct a tunnel rather than repair the current routes.

Lighting effects in the longest road tunnel in the world


Beginning in 1995, work on the tunnel's construction was done simultaneously from three different places and included drilling, blasting, loading and removing materials, and anchoring the rock mass.

The tunnel was dug using both traditional drilling and blasting techniques and a computer-controlled drilling equipment. The drilling and blasting procedures have to be executed with extreme accuracy in order to guarantee geometric correctness. The permanent measuring sites in regard to which measurements were taken inside the tunnel were determined using the GPS system.

For each blasting, around 100 boreholes with a diameter of 45 to 51 mm and a depth of up to 5.2 metres were bored. During each blasting, 500 kg of explosives were utilised to split the rock mass into smaller pieces. It was necessary to secure the tunnel's walls and vault before continuing to drill. Rod anchors and a particular kind of shotcrete with a reinforcing mesh were put to the rock's face for this reason.

The tunnel's external look and inner layout received particular consideration. The interior of the tunnel was designed by a special team of psychologists to prevent boredom when travelling through it.

The tunnel is broken into four sections: the primary section and three galleries spaced six kilometres apart. All areas of the tunnel now have a lighting setup that mimics dawn's natural light. In order to simulate daybreak, the galleries are illuminated with blue-yellow lights while the main area is lit with white light.

One of the safest tunnels in the world, the Laerdal tunnel is shut down entirely if the ventilation system fails if there is an excessive amount of exhaust gas present.

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