An underground full-face tunnel can be dug by a tunnel-boring machine (TBM) in a single mechanical operation using drilling. They function in a range of environments, including sandy or clay soils, sedimentary and volcanic rock, and more. Typically, they weigh more over 6,000 tons and span more than 150 meters.
Certain aspects of the terrain and the tunnel that has to be excavated must be met in order to use a tunnel-boring machine. Since the machine is unable to perform abrupt bends, the latter must have enormous radii of curvature. This explains why the machine is often highly priced. Costs for those with a diameter of 4 to 6 meters can reach €11 million, while those with a diameter of 15 meters can go up to €25 million.
Shoring systems, or temporary confinement devices, can also be installed using a tunnel-boring machine to support excavations and structures during building operations.
How does a machine that digs tunnels operate?
Typically, a tunnel-boring machine uses a motor with an electric or hydraulic system to create a hole in the earth while its spinning head completes the excavation work. The tunnel boring machine with cutting components made of various materials and forms. Both rely on the features of the tunnel.
The pushing power of the tunnel-boring machine is produced by perimeter jacks resting on rings, which are then forced up against the tunnel wall by further jacks. By doing this, the machine gains sufficient strength and grip to allow the rotary head to continue drilling.
A platform known as “lagging equipment” or “buck-up” is situated on rails behind the tunnel-boring machine. On this platform are additional pieces of work equipment, including fans, transformers, and a belt to remove the material being dug.
The tunnel-boring machine pauses once the excavation is complete, and the next step is to attach the rings that will stabilize the tunnel construction. To do this, voussoirs—prefabricated, reinforced concrete pieces—are utilized.
What Kinds Of Tunnel-Boring Devices Exist?
There are two major categories into which tunnel-boring machines fall:
- A tunneling machine is made to dig through hard or semi-hard rock without the assistance of a support structure. Through thrust cylinders, its pushing power is transmitted to the spinning cutting head. This kind of tunnel-boring equipment isn’t used for temporary shoring since it doesn’t have steel cylinders behind the cutting wheel.
- Shields: made to dig in areas where building support systems is necessary. Usually, these are soils made of soft rock. In order to assist the construction of the final shoring that secures the stability of the tunnel, the shields are equipped with an exterior metal chassis that serves as a temporary ground support. This chassis is positioned from the front.
Open front, closed front, pressured closure with trapped air, hydro shields, mechanical closure, earth pressure balance shields (EPB), and hydro shields are some examples of the types of shields.
A third set of double-shield tunnel boring devices exists. Depending on the condition of the rocky terrain, this kind of tunnel-boring machine can function as a shield or as a tunneling machine. This option is perfect for areas of terrain that alternates between dirt and rock.
What distinguishes a wall chaser from a tunnel-boring machine?
While there are several techniques for mechanically digging tunnels, wall chasers and tunnel-boring machines stand out the most. Even though they both serve the purpose of excavation, there are notable distinctions between them, including:
- Wall chasers are tunnel-boring machines that run on belts and include an articulated arm with friction spikes in addition to their spinning head.
- Wall chasers are utilized to excavate portions of ground with low to medium resistance, and tunnel-boring machines are employed for terrain with significant strength.
- Wall chasers are utilized for civil engineering and building projects with excavation lengths of no more than two kilometers, whereas tunnel-boring machines are capable of doing projects with lengthier excavations.
What Qualifications Should A Person Operating A Tunnel-Boring Equipment Have?
Operators must fulfill specified qualifications and possess specialized expertise in order to handle and operate a tunnel-boring equipment, such as:
- The Application Of Safety Gear On Building Sites.
- Delivering Supplies To Be Utilized In The Project.
- Drilling Machine Use.
- Protecting The Infrastructure For Services And Avoiding Harm When The Equipment Is Operating.
- Comfortable Work.
- Wearing A Harness, Safety Shoes, Helmets, Gloves For Protection, And Clothes With Reflective Stripes.
- Awareness Of The Appropriate Protocols For Responding In An Emergency.
- Adherence To Construction Site Safety And Health Regulations.
- Wearing Headphones Or Earplugs As A Kind Of Hearing Protection.