T — Dictionary of Quarrying Terms

TNT: abbr. trinitrotoluene, a military explosive compound used industrially as a sensitizer for slurry-type explosives.

TQM: abbr. see ‘total quality management’.

tacheometer: A surveying instrument fitted with a telescope which measures distance by sighting a levelling staff. In its simplest form the intercept beween the two stadia lines and the vertical angle are read and from these readings the distance between the tacheometer and the staff is calculated.

tachograph: A speedometer incorporating an integral electric clock and a chart recording mechanism. It is fitted into the dashboard of commercial vehicles and permanently records the speed of the vehicle, the total distance travelled and the distance between stops, the driving time and standing time.

tack coat: A thin film of binder to improve adhesion between courses in a road formation.

tail end: The opposite end of a conveyor to the delivery end.

tailings: Waste material which has been rejected in a mineral processing operation. Often occur as a slurry comprising finely divided material in suspension, requiring prolonged settlement.

tamping rod: A rod or bar used for the hard compaction of concrete in the compacting factor, slump or cube tests.

tangent screw: A fine-adjustment screw fitted on both the horizontal and vertical circles of a theodolite for the purpose of moving the line of sight through small angles.

tar: A viscous liquid, black in colour, having adhesive properties and obtained by the destructive distillation of coal, wood, shale etc.

tare: The weight of an empty truck or other container.

tectonics: The study of the structures resulting from the deformation of the Earth’s crust.

temperature: The degree of hotness or coldness of a substance. Temperature is measured on either the Celsius scale or the thermodynamic scale in degrees Celsius (C) and Kelvin (K) respectively. Celcius and Kelvin degrees represent equal intervals of temperature but the Kelvin scale takes as its zero absolute zero which is approximately -273°C.

ten percent fines value: A measure of the resistance of an aggregate to crushing as determined by the ten percent fines test defined in BS 812 now replaced by Los Angeles test.

tensile test: Test carried out on metal specimens of standard dimensions to investigate the ability of the metal to withstand tensile loading.

terrace: An alluvial deposit laid down by an ancient river flowing at a higher level than the present river level.

Tertiary: The era following the Mesozoic, ranging in time from 65 million to 2 million years ago, and the corresponding series of rocks.

tertiary crushing: The third stage of size reduction mineral (less than 20mm or even 10mm).

test cubes: 150mm or 100mm cubes of concrete on which compressive strength tests are carried out. Details of the making and curing of test cubes are given in Parts 108 and 111 of BS 1881.

texture depth: An indication of the state of wear of a road surface and its likely resistance to skidding.

theodolite: Surveying instrument used for the accurate measurement of both horizontal and vertical angles.

thermistor: A semi-conductor the resistance of which is very sensitive to temperature; used to monitor temperature changes in the windings of electric motors.

thermodynamics: The science dealing with the relationship between thermal energy (heat) and all other forms of energy (mechanical’ electrical etc).

thickener: Large circular tank in which solids settle slowly and form a slurry which is continuously removed from below while fairly clear water overflows. Also called a clarifier.

three-cone (tri-cone) bit: see ‘roller rock bit’.

three-phase system: A system of electrical energy generation and transmission in which there are three phases and the phase displacement is 120°.

throughput: The mass of material passing through a specified treatment in a given time; usually measured in tonnes/h.

throw: 1 The amount of vertical displacement caused by a fault. 2 Lateral displacement of a screen or crushing surface in motion.

thrust bearings: Bearings which support rotating shafts loaded axially, ie with a load parallel to the axis of the shaft.

thyristor: A silicon-controlled semi-conductor device for switching between high conductivity and non-conductivity. One of their many uses is in the speed control of dc motors.

tie: A structural member sustaining only a tensile load.

till: Unsorted drift deposited by a glacier and comprising clay, sand, gravel and boulders.

time study: see ‘work measure. ment’.

tine: An excavating point or tooth in the leading edge of an excavator bucket or ripper attachment.

toastrack: A processed aggregate stocking arrangement in bays separated by concrete walls or timber divisions. Aggregate is fed in by overhead conveyor and may be withdrawn by wheeled loading shovel or by belt conveyor via an underground reclaim tunnel.

toe: The rock left unbroken at the foot of a quarry face after a blast.

toe hole: A horizontal or upwardly inclined shothole placed at the foot of a quarry face.

toggle-plate: A plate used as a link or element in a machine designed to withstand thrust and hinged at both ends. See ‘singletoggle jaw crusher’ and ‘double-toggle jaw crusher’.

ton: The long ton of 2,240 lb equivalent to 1.016 metric tonnes. See ‘short ton’.

tonne: The metric tonne of 1,000kg.

topography: A description of the natural and man-made features of an area.

topsoil: The uppermost layer of soil, generally containing a high proportion of organic matter, that can support vegetation.

torque: The turning moment of a couple equal to either force of the couple multiplied by the distance between the forces. Symbol: T. Units: Nm.

torque converter: A hydraulically operated device which acts as an infinitely variable gear.

total costing: The costing technique whereby the calculated cost of a product includes the share of the fixed overheads which are considered attributable to it. Total costs are essential where work is being carried out on a cost-plus basis.

total loss control: A concept of accident investigation and prevention which takes into account such matters as damage to property and equipment, lost time, wasted materials etc.

total quality management: A complete management philosophy developed in Japan in the 1950s and 60s which embodies quality control procedures and quality assurance techniques. abbr. TQM.

total station: A surveying instrument combining electronic distance measuring and tacheometry.

tractive effort: The force which an engine or tractor is able to exert at the draw-bar.

tractor: A self-propelled vehicle which travels on either crawler tracks or on wheels, intended primarily to exert a powerful tractive force for moving other machines, but often used as a mount for other equipment, the combination forming a self-contained unit, eg a bulldozer.

trailing cable: A flexible cable carrying the power supply to transportable electrical apparatus, eg a dragline.

trailer dredger: A large, powerful type of suction dredger which drags the suction pipe along behind it while steaming ahead. See ‘anchor dredger’.

trainee shotfirer: A person appointed by the manager in accordance with regulation 26 of the Quarries Regulations 1999. A trainee shotfirer is not permitted to fire shots until the manager is satisfied that he has completed a suitable period of training and appropriate practical experience, and except when he is under the close personal supervision of a shotfirer. For training of appointees see the Approved Code of Practice.

tramp iron: Pieces of metal (eg bucket teeth) which have been removed with the mineral and which would damage crushing machinery if allowed to enter.

transducer: General term for a device which converts a physical magnitude of one form of energy into another form. An electric motor is an electromechanical transducer.

transformer: A highly efficient item of electrical plant the function of which is to change the voltage of an alternating current supply. see ‘current transformer’.

transmission: The means by which power is transmitted from the engine of a vehicle to the road wheels through the clutch, gears, propeller shaft, differential gear etc.

transverse waves: Waves where the particles of the medium move at right-angles to the direction of movement.

trenching: The digging of trenches in the proving of overburden, unconsolidated sands and gravels.

trial pit: A hole dug to prove an alluvial mineral deposit or the depth to bedrock.

triangulation: The process of dividing a large area into a network of triangles for survey purposes. All the angles and one side of one of the triangles (the base line) are accurately measured.

Triassic: The earliest period of the Mesozoic era between 248 million and 213 million years ago, and the corresponding rocks.

trimmers: Shots, at the periphery of an excavation, fired to give the excavation its final outline.

trommel: A rotary screen for sizing aggregate, coal or ore. It consists of a cylindrical shell of perforated plate or wire cloth, mounted on a central shaft inclined at a small angle to the horizontal. It may also be fitted to the discharge end of a washing barrel or scrubber.

truckmixer: A truck-mounted concrete mixer which mixes ready-mixed concrete and transports it from the batching plant to the customer; where it serves a mixing plant, it functions only as an agitator.

true dip: see ‘full dip’.

tub: The large circular base on which a walking drag line sits during operation.

tuff: Compacted fine volcanic ash and dust.

tungsten carbide: A hard-wearing material used for drill-bit tips and inserts.

turbocharging: The boosting of the induction pressure of a supercharged internal-combustion engine by means of a turbine driven by the exhaust gases from the engine.

turnbuckle: A long nut screwed internally with a right-handed thread at one end and a left-handed thread at the other. It is used to connect two rods which are to be joined together so that when the nut is tightened it draws the ends together, providing a means of adjusting the total length.

turnover: The gross revenue earned by a company as a result of its operations and sales.

two-bearing screen: A mechanically vibrated screen in which the circular motion is generated by the rotation of out-of-balance weights attached to a shaft held in two bearings, one in each of the screen side-plates.

two-stroke cycle: An internal combustion engine cycle completed in two piston strokes, the charge being introduced into the cylinder, compressed, expanded and exhausted through ports in the cylinder wall, before and during the introduction of the fresh charge. Every downward stroke generates power.

Type 1: Granular sub-base using crushed rock as specified in the Department of Transport Specification for Highway Works 1991.

Type 2: A lower-quality granular sub-base than Type 1 which may comprise as-dug sand and gravel.