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Tail skin
tailskinA rear end shield forming a tail seal and used for building the segmental rings.


TAM (tube a manchette)
A Manchette tube is a PVC or metal pipe in which rubber sleeves cover holes that are drilled in the pipe at specific intervals. The tubes are inserted into holes that have been bored into the "work area" (soil, rock, concrete, etc.) known as the "grout zone". Grout is pumped to a packer that has been slid into the tube, seals on the packer force the grout through the holes in the tube, past the flexible rubber sleeve, and into the grout zone to help stabilize and/or seal it.

Tape extensions
A Tape Extensometer is a portable device, designed to measure the relative distance between reference anchors fixed to the excavation or structure.

Taper
This refers to the gradient across the circumferential face of a segmental lining. Rotation of successful rings allows curves to be negotiated.

TBMTBM – (tunnel boring machine)
A machine for excavating circular tunnels, a rotating cutting wheel breaks the ground, which drops through slots in the cutting wheel for removal.

Thrust load
The total amount of force a tunnel boring machine can apply onto the face of an excavation.

Thrust pit
Pit or shaft located at the beginning of a pipe jacking operation.

Timber packer (mining engineering)
One who builds packs or pack walls. In anthracite and bituminous coal mining, one who fills worked-out rooms, from which coal has been mined, with rock, slate, or other waste to prevent caving of walls and roofs, or who builds rough walls and columns of loose stone, heavy boards, timber, or coal along haulage ways and passageways and in rooms where coal is being mined to prevent caving of roof or walls during mining operations. Also known as packer; pillar man; timber packer; waller. Also known as the thin shins placed between segment joints to covert geometry and aid the negotiation of curves.

Tolerances
Specified parameters for construction or manufacture of a particular item or component.

Top heading
A small tunnel dug ahead of the main excavation, they are dug at the crown of the tunnel. Top headings are used in the top-heading-and-bench method, the main advantage being that engineer can use the heading tunnel to gauge the stability of the rock before moving forward with the project.

tunnelTunnel
An underground passage, open to daylight at both ends. If open only at one end, it is called a drift or an adit. A tunnel is a horizontal or sloping underground enclosed way of some length.


Tunnel lining
Permanent or temporary cover to the rock or soil surface at the periphery of a tunnel excavation.

tunnel ventilationTunnel ventilation
Tunnel ventilation and smoke extraction are essential to the design of safe tunnels; its purpose is to provide a safe and comfortable environment for users during the operational stage of the tunnel and to the workers during the construction phase.


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