Tunnelling and underground construction
Expert-defined terms from the Advanced Certificate in Engineering Geology and Soil Mechanics course at Greenwich School of Business and Finance. Free to read, free to share, paired with a globally recognised certification pathway.
Tunnelling and Underground Construction Glossary #
Tunnelling and Underground Construction Glossary
Anchor Plate #
Anchor Plate
Anchor plates are large steel plates that are used to support the ends of rock b… #
They are designed to distribute the load from the rock bolt to a larger area of the rock mass, preventing the bolt from pulling out.
Backfill #
Backfill
Backfill refers to the material used to refill an excavated area, such as a tunn… #
The backfill material is typically chosen to provide stability and support to the tunnel structure.
Backhoe #
Backhoe
A backhoe is a type of excavating equipment that consists of a digging bucket on… #
Backhoes are commonly used in tunnel construction to remove soil and rock from the excavation site.
Benching #
Benching
Benching is a method of excavation in which the tunnel face is cut back in steps… #
Benching helps to prevent rockfalls and collapses during excavation.
Blasting #
Blasting
Blasting is a common method used in tunnel construction to break up rock and soi… #
Explosives are placed in drill holes and detonated to create the necessary space for the tunnel.
Compaction grouting #
Compaction grouting
Compaction grouting is a technique used to improve the stability of soil and roc… #
Grout is injected into the ground under pressure, compacting the surrounding material and increasing its strength.
Crown #
Crown
The crown of a tunnel is the highest point of the tunnel's cross #
section. It is typically arched to provide structural support and distribute the weight of the overlying material.
Cut and Cover #
Cut and Cover
Cut and cover is a method of tunnel construction in which a trench is excavated,… #
This technique is commonly used in urban areas where space is limited.
Deformation #
Deformation
Deformation refers to the changes in shape or size of a tunnel or surrounding ro… #
Monitoring deformation is important to ensure the stability of the tunnel structure.
Excavation #
Excavation
Excavation is the process of removing material from the ground to create a tunne… #
Excavation methods vary depending on the type of material being excavated and the desired tunnel shape.
Face Stability #
Face Stability
Face stability refers to the ability of the tunnel face to resist collapse durin… #
Proper support systems and excavation techniques are essential to maintain face stability.
Geotechnical Investigation #
Geotechnical Investigation
Geotechnical investigation involves studying the physical properties of soil and… #
This information is used to design safe and stable tunnels.
Ground Freezing #
Ground Freezing
Ground freezing is a technique used in tunnel construction to stabilize the grou… #
Pipes filled with a freezing agent are installed, lowering the temperature of the surrounding soil and rock to create a frozen barrier.
Ground Improvement #
Ground Improvement
Ground improvement techniques are used to strengthen weak or unstable soil and r… #
Methods such as compaction grouting, jet grouting, and soil mixing can be used to improve ground conditions.
Heading #
Heading
The heading is the front or face of the tunnel where excavation is taking place #
It is typically the first part of the tunnel to be constructed and requires careful monitoring to ensure stability.
Inverted Arch #
Inverted Arch
An inverted arch is a type of tunnel support structure that is installed on the… #
It helps to distribute the weight of the overlying material and provides additional support to the tunnel structure.
Jet Grouting #
Jet Grouting
Jet grouting is a ground improvement technique that involves injecting high #
pressure grout into the ground to create a column of soil-cement. This method is often used to stabilize soil and rock mass around tunnels.
Key Block #
Key Block
Key blocks are large blocks of rock that are left in place during tunnel excavat… #
They help to prevent collapses and provide stability to the tunnel structure.
Lining #
Lining
The lining of a tunnel refers to the structure that is installed to support the… #
Linings can be made of concrete, steel, or other materials, depending on the tunnel design and ground conditions.
Microtunneling #
Microtunneling
Microtunneling is a trenchless method of tunnel construction that uses a remote #
controlled machine to excavate tunnels with a small diameter. This method is often used for installing utility pipelines underground.
Needle Beam #
Needle Beam
A needle beam is a temporary support structure used in tunnel construction to pr… #
It is typically made of steel beams and installed behind the tunnel face during excavation.
Oversize Excavation #
Oversize Excavation
Oversize excavation refers to the process of excavating a larger area than is ne… #
This extra space allows for the installation of support systems and provides a safe working environment for construction crews.
Permeation Grouting #
Permeation Grouting
Permeation grouting is a technique used to improve the stability of soil and roc… #
The grout permeates the surrounding material, filling voids and increasing strength.
Quality Control #
Quality Control
Quality control in tunnel construction involves monitoring and testing materials… #
Quality control measures help to prevent defects and ensure the long-term durability of the tunnel.
Rock Bolt #
Rock Bolt
A rock bolt is a long steel rod that is inserted into drill holes in the rock ma… #
Grout is often injected around the rock bolt to anchor it in place.
Shotcrete #
Shotcrete
Shotcrete is a sprayable concrete mixture that is commonly used in tunnel constr… #
It is applied using a high-pressure hose, providing a quick and efficient way to create a durable tunnel lining.
Thrust Boring #
Thrust Boring
Thrust boring is a trenchless method of tunnel construction that uses a drilling… #
This method is often used for installing pipelines and conduits underground without disturbing the surface.
Underpinning #
Underpinning
Underpinning is a technique used to strengthen the foundations of existing struc… #
Various methods, such as micropiles, jet grouting, and compaction grouting, can be used for underpinning.
Ventilation #
Ventilation
Ventilation systems are installed in tunnels to provide fresh air and remove har… #
Proper ventilation is essential to ensure the safety of workers and maintain air quality in the tunnel.
Waterproofing #
Waterproofing
Waterproofing is the process of applying materials to the tunnel lining to preve… #
Waterproofing membranes, coatings, and sealants are commonly used to protect the tunnel structure from water damage.
Excavation Face #
Excavation Face
The excavation face is the front of the tunnel where excavation is taking place #
It is typically supported by temporary or permanent support systems to prevent collapses and maintain stability during construction.
Yieldable Steel Sets #
Yieldable Steel Sets
Yieldable steel sets are support structures made of steel beams that are install… #
The steel sets are designed to yield or deform under pressure to absorb the energy from rock movements.
Zoning #
Zoning
Zoning refers to the division of tunnels into different zones based on the geote… #
Zoning helps to optimize construction processes and ensure the safety and stability of the tunnel.
Conclusion #
Conclusion
This glossary provides a comprehensive overview of key terms and concepts relate… #
By understanding these terms, engineers and geologists can effectively plan, design, and construct tunnels that are safe, durable, and sustainable. Each term is explained in detail, with practical examples and applications to enhance learning and understanding. Whether you are new to the field of engineering geology and soil mechanics or looking to expand your knowledge, this glossary serves as a valuable resource for mastering the fundamentals of tunnelling and underground construction.