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Radial joint
Joints in a pre-cast concrete segmental tunnel perpendicular to the circumference.

ramRam
A hydraulic operated thrusting member in a
Tunnel Boring machine (TBM) that assists in moving the TBM forward by shoving off pre-cast concrete segmental tunnel lining.


Rib
Circular or arch support (usually steel I beams) used to support/strengthen excavations, often used in conjunction with timber boards (ribs and logging).

Ring (number, closure, closure distance)
Pre-cast concrete segmental lining of finite length.

Ring beam
This is a ring-shaped structural member usually carrying bending/vertical gravitational loads.

RMR – (Rock Mass Rating)
The sum of six rock quality parameters (unaxial compressive strength of rock material, rock quality designation (RQD), spacing of discontinuities, condition of discontinuities, groundwater conditions and orientation of discontinuities). Scale 0-100.

Road header
Excavating equipment consisting of a boom-mounted cutting head, a loading device usually involving a conveyor, and a crawler travelling track to move the entire machine forward into the rock face. Similar to a profiler.

robotRobot (for spraying concrete)
A robot, attached to the rear of a tunnel boring machine, for spraying a concrete lining onto the perimeter of the tunnel.


Robotic spraying
Spraying of concrete to create a tunnel lining by means of remote or automated control.
(see Robot for picture)

Rock
Materials consisting of the aggregate of minerals, like those making up the Earth's crust that has not been broken down into loose material.

Rock arch
This is the phenomenon of rock around an underground excavation behaving as an arch, transferring compressive loads to either side of the excavation. A self supporting excavation shape where the rock is broken to form a natural and stable arch.

Rock bolt
This a long bolt for stabilising rock excavations by transferring loads into the confined strong rock interior.
running tunnel
Running tunnel
This is the basic section of a tunnel between stations,shafts, turnouts etc.




^{If you think we have omitted a term, email us at tunnels.webmaster@mottmac.com}