C — Dictionary of Quarrying Terms

CAD: abbr. computer-aided design.

CAM: abbr. computer-aided management.

CBGM: abbr. cement-bound granular material.

CCTV: abbr. closed-circuit television.

CECE: abbr. Committee for European Construction Equipment.

CEN: abbr. Comite Europeen de Normalisation. The European Community standards organization.

CENELEC: abbr. Comite Europeen de Normalisation Electrotechnique. The European Community electrical standards body.

cmr: abbr. see ‘continuous maximum rating’.

COSHH: abbr. Control of Substances Hazardous to Health Regulations.

CSS: abbr. closed-side setting. See ‘setting’.

cable: A number of insulated conductors protected by armouring and other covering.

cable ducts: Concrete, earthenware, plastic or steel pipes through which cables are drawn and in which they rest.

cage motor: see ‘squirrel-cage motor’,

California bearing ratio CBR: A relative value which expresses the bearing capacity of a soil or pavement layer in comparison with a result obtained by using a standard crushed rock material. It is determined by the test procedures defined in BS 1377.

calcite: Calcium carbonate, CaCO₃. Occurs in a variety of crystal forms which are usually white or yellowish in colour. Rhombohedral; relative density 2.7; hardness 3. It is the main constituent of chalk, limestone and marble.

calendered rubber: Rubber which has been passed through a machine, generally consisting of a number of vertical rollers, in order to ensure uniform thickness.

calfdozer: A small bulldozer.

caliper: An instrument used in conjunction with a microlog which, when lowered down a borehole, measures and records the internal diameter throughout its depth.

calorie: The quantity of heat required to raise the temperature of 1 gramme of water by 1°C. This is the unit quantity of heat on the CGS system and is replaced by the joule on the SI system. 1 calorie = 4.186J.

calorific value: The amount of heat given out when unit mass of a fuel (or unit volume in the case of a gas) is burned completely. In fuels containing hydrogen the value must be related to the temperature at which the measurements are made, because on this depends whether or not the water vapour produced is condensed, giving up latent heat. Units: kJ/kg and kJ/m³.

calyx drilling: A method of rotary drilling using a toothed cutting bit or chilled shot.

camber: The convexity given to the curved cross-section of a carriageway etc.

Cambrian: The earliest period of the Palaeozoic era between about 590 and 505 million years ago, and the corresponding system of rocks.

candela: The SI unit of luminous intensity which is the quantity that describes the capacity of a source or illuminated surface to emit light in a given direction. Symbol: cd.

cantilever: A beam which is firmly secured at one end and free at the other.

cap: see ‘detonator’.

capacitance: The capability of two conductors separated by an insulator to store an electric charge. Symbol: C. Units: farads.

capacitor: A circuit element which when charged stores electrical energy.

capital: Money invested in a business by its owners to earn income.

capped fuse: A detonator fitted with a length of safety fuse.

carbon monoxide: A highly poisonous, tasteless, odourless gas which is a product of incomplete combustion of inorganic material, eg when an internal combustion engine is idling. It is also created when explosive materials are detonated. Excessive carbon monoxide is caused by an inadequate amount of oxygen in the explosive mixture (excessive fuel). Symbol: CO.

Carboniferous: The geological period of time 360 to 286 million years ago and the corresponding system of rocks. In Britain Carboniferous rocks are an important source of crushed rock aggregate.

cardan shaft: A propeller or driving shaft which conveys the power from the gearbox to the differential of a motor vehicle. It is usually connected through universal joints to permit displacement of the rear axle on the suspension.

Cartesian co-ordinates: Rectangular co-ordinates. See ‘co-ordinates’.

cartridge: An individual unit of explosive, usually wrapped in the form of a cylinder.

cartridge dust collector: An alternative to a bag filter which uses lower filtration velocities and is more compact.

case-hardening: Surface hardening of steel by heating in a carbonaceous medium to increase the carbon content in the surface layers, then quenching.

cash flow: The movement of cash into and out of a company.

casing: Piping used to support the sides of a borehole. Flush-coupled casing is joined with a coupling which has the same outside diameter as the casing, but has two male-threaded ends. Flush-joint casing has a male thread at one end and a female thread at the other; no coupling is used.

casing drive hammer: A weight used to drive casing down a hole.

cast iron: An iron-carbon alloy containing more than 1. 7% and usually above 2.5% carbon including substantial amounts of graphite. It is very fluid when molten and is suitable for making intricate castings by pouring into sand moulds. Applications include: cylinder blocks, hydraulic cylinders, crusher frames etc.

catchment area: The area drained by a stream or river or supplying a reservoir.

catenary: The curve into which a uniform, inextendable rope falls when suspended from its ends.

cavitation: The formation of a cavity between the impeller blades of a centrifugal pump and the water normally in contact with it. This leads to the liberation of oxygen and corrosion of metal parts.

cement: 1 The matrix of a sedimentary rock. 2 The manufactured powder which, through the addition of water, binds together aggregate particles into concrete.

cement stabilization: The consolidation of a foundation layer through the use of low cement content with fill material or subsoil.

cement-bound macadam: A form of road construction in which a mortar of Portland cement and sand is added to coarse aggregate.

cementation: The injection of cement grout under pressure into fissured rocks to strengthen and make them impervious to water.

centi.: A prefix meaning one hundredth.

centre of gravity: The point in a body at which the entire mass of the body may be regarded as being concentrated.

centrifugal force: The reaction to a centripetal force, acting radially outwards from the centre of rotation.

centrifugal pump: A pump with a rotating impeller which imparts an angular acceleration to the liquid, causing it to flow outwards from the centre to the periphery.

centripetal force: The force which must be applied to a body to cause it to follow a circular path. The centre of the path produced lies in the direction of the applied force, hence the name centripetal or centre-seeking force.

ceramics: Articles produced by the firing of minerals, especially clay, at very high temperatures.

chain block: see ‘differential pulley block’.

chain-curtain feeder: A feeder in which loops of heavy chain suspended from a rotating drum control the rate of flow of material from the chute into the primary crusher.

chain survey: A linear survey in which no angles are measured, only lengths. .

chainage: A length measured by means of a chain or steel tape.

chamber: 1 An excavation to accommodate an explosive charge. 2 The cavity within a crusher in which the rock is subjected to crushing action.

chambering: see ‘springing’.

charge: The quantity of explosives in a particular shothole.

check valve: see ‘non-return valve’.

cheek plates: The liners on the two sides of the crushing chamber of a jaw crusher.

chequered plate: Patterned or perforated metal plate used to make non-slip flooring in mineral preparation plants, power stations etc.

chilled shot bit:A flat-surfaced bit used with hardened steel shot to drill rock by a milling action.

china clay: see ‘kaolin’.

chippings: Single-size aggregate nominally between 3mm and 25mm inclusive.

chisel bit: A percussive drill bit having a single cutting edge.

choke: see ‘inductor’.

choke point: That zone of a crushing chamber, usually near the outlet, where the capacity is at a minimum. It is in this zone that choking is most likely to occur.

choke-fed: The sustained feed to a cone crusher which ensures that the crushing zone remains over-full at all times. This results in a more cubical-shaped product, with the best shape occurring in the aggregate size at the crusher setting.

choking: A stoppage of the downward flow of rock through a crusher usually caused by the packing of compressed fines near the discharge point.

churn drill: A cable drill used to drill vertical holes by raising and dropping the heavy drilling tool on the end of a steel wire rope.

circuit tester: An instrument used to test series circuits in electrical shotfiring for continuity and resistance.

circuit-breaker: A device for automatically making or breaking an electrical circuit under both normal and abnormal conditions, such as when a short circuit occurs.

circulating fluid: The fluid, which may be water, mud or air, circulated through the apparatus during drilling. Its chief functions are to remove cuttings, to cool the bit and, in the case of mud, to support the sides of the hole.

clamping screw: On surveying instruments a screw for clamping a vernier before the tangent screw can be used for fine adjustments.

clamshell: A twin-jawed bucket used with a crane jib for digging and loading loose material, eg sand and gravel from a flooded deposit.

clarifier: A thickener used to separate slimes and wash water.

classification: The separation of particles according to their size, density and shape by control of their settling rate through a fluid medium.

classified tip: An obsolete term for a tip registered under the Mines and Quarries (Tips) Regulations 1971 because of its hazard potential, see notifiable.

classifier: A device which separates particles according to their size, shape and density by physical means other than screening.

clastic: Deposits consisting of broken fragments of earlier rocks.

clay minerals: Silicate minerals which are mainly formed by the weathering or alteration of feldspars and other primary minerals. Kaolin is one example.

cleaner cells: Flotation cells used in the retreatment of a rough concentrate to improve its quality.

cleavage: I In a crystalline mineral, one or more series of parallel planes along which the mineral tends to split. 2 In a rock, definite parallel closely spaced planes along which it may split, and which may be highly inclined to the bedding planes.

clevis: A V-shaped metal bar drilled in a number of places. One of its uses is to hold the shank of a ripper in any of several positions so that depth and tooth angle may be adjusted to meet prevailing conditions.

clinker: I The fused product from a cement-making kiln which is subsequently ground into powder. 2 Sintered or fused furnace ash which may be used for hard core or aggregate for concrete blocks.

clinometer: An instrument used to determine the amount and direction of deviation of a blasthole from the vertical or a hand-held instrument for the measurement of angles of slope.

closed circuit: I An electrical circuit that provides an uninterrupted path for the current. 2 A system in which the product from a crusher passes to a screen, the overflow from which is returned to the crusher for further treatment and the underflow released from the closed circuit.

closed traverse: A traverse which begins and ends at the same point; its accuracy can therefore be checked.

closing error: In a closed traverse, the discrepancy between the starting point and the finishing point as calculated from the measurements taken. The error, if small enough, may be distributed throughout the series of measurements.

coal preparation: Collectively, physical and mechanical processes applied to coal to make it suitable for a particular use.

coarse aggregate: Graded stone or gravel over 4mm in size for use in concrete or 2mm for coated material.

coated chippings: Aggregate chippings which have been coated thinly with bituminous material for scattering over a wearing course or for use as a surface dressing. Where bitumen is added just sufficiently to present a prepared surface for added bitumen, the term ‘lightly coated chippings’ is used.

coated grit: Grit which has been coated thinly with tar or bitumen binder of such proportions and of such properties as to allow it to be scattered for blinding a wearing course.

coated macadam: A road material consisting of graded aggregate that has been coated with tar or bitumen, or a mixture of the two, and in which the interlocking of the aggregate particles is a major factor in the strength of the roadbase or surfacing. ‘

coating plant: A general term used to cover any installation which produces coated material either as a macadam or an asphalt.

coefficient of friction: The ratio of the limiting friction to the normal reaction between the two surfaces.

coincidence bubble: An arrangement fitted to precise levelling instruments which enables the surveyor to sight half of each end of the bubble at the same time, with the images of the two halves side by side.

cold asphalt: Historically, a term used for warm laid, fine bitumen macadam (ie neither ‘cold’ nor ‘asphalt’). It does not occur within current British Standards.

cold feed: A system of storage hoppers used to supply aggregate to a coating plant.

cold planer: A machine fitted with milling cutters for smoothing, or milling out a road surface up to 150mm in depth, without it first being softened by the application of heat.

collaring: The operation of starting to drill a hole.

collector ring: The conductor ring through which the power is transferred from the carriage or tub of an electrically operated shovel or dragline to the rotating body of the machine.

collectors: 1 A type of flotation reagent. They are organic compounds which render selected minerals water-repellent by absorption of molecules on the mineral surface, thus enabling mineral particles to attach themselves to air bubbles on contact. 2 A means of making an electrical connection between the moving parts of a machine and the supply, eg collector rings on an excavator.

collimation line: The line of sight of a surveying instrument.

collimation method: In levelling, a method of calculating reduced levels by subtracting staff readings from the level of the line of sight (collimation line) of the instrument. This method is usually favoured where it is required to obtain the levels of many points from one set-up.

column charge: A continuous charge in a quarry blasthole.

comminution: Size reduction of rocks and ores by crushing and grinding using compressive, impact and abrasive forces.

commutation: The action of transferring current between the armature conductors, through the commutator segments and brushes, and the external circuit of an electrical machine.

compacting factor test: Test for the workability of freshly mixed concrete by weighing the concrete which will fill a container of standard size, firstly when allowed to fall in under standard conditions and then when filled and compacted a layer at a time. The compacting factor is the ratio of the partially compacted weight to the fully compacted weight; a higher value indicates greater workability.

compaction: The process of packing soil or aggregate particles more closely together, to increase the density.

compactor: see ‘roller and compactor’,

compound-wound motor: A dc motor having field windings connected in both parallel and series with the armature, If the polarity of the series winding is such as to assist the main poles, the motor is cumulatively compound-wound and, if in opposition, it is differentially compound-wound,

compression crushers: Crushers in which the rock is subjected to a squeezing action. This group includes gyratory, jaw and smooth rolls crushers.

competent: as defined by the Quarry Regulations 1999, in relation to a person means a person with sufficient training, experience, knowledge and other qualities to enable him to properly undertake the duties assigned to him.

compression test: Test in which specimens of the material under test (eg concrete) are subjected to increasing compressive force until they fail by buckling, cracking or disintegration.

compressor: see ‘air compressor’.

concaves: The cast manganese liners of the chamber of a gyratory crusher.

concrete: A mixture of stone, sand, water and a binder, usually Portland cement, which hardens to a stone-like mass.

concrete aggregates: Grading limits for concrete aggregates are given in BS EN 12620

condition: In relation to a planning consent, a limitation imposed by the MPA to achieve some desirable effect in relation to the permitted development.

condition monitoring: A series of engine assessment techniques based on oil testing.

conditioning: The preparatory stage in the flotation process in which the reagents are brought into intimate contact with the solids of the pulp.

conductivity meter: An instrument which gives a continuous readout of the chloride ion content of wash water used in marine aggregate processing.

conduit: Pipe or trough to contain and protect cables or wires.

cone crusher: A gyrating compression crusher with both fIxed and moving crushing members of greater diameter at the bottom than at the top and with mainly secondary and tertiary crushing applications.

conglomerate: A rock consisting of rounded pebbles held together by a natural cement.

construction joints: A joint between fresh concrete and concrete which has already hardened. Concrete on either side of the joint is usually united by reinforcement crossing the joint.

contact metamorphism: Changes brought about in a rock by contact with intruded or extruded molten igneous material.

contactor: A device for repeatedly opening and closing electrical circuits.

continuous asphalt plant: A heating, mixing and storage installation, particularly suited to the production of high volumes of hot-rolled asphalt. See ‘drum-mix plant’.

continuous maximum rating: The load at which an electric motor can be continuously operated without overheating. abbr. cmr.

continuous mixer: A concrete mixer which receives a ribbon feed of raw materials at one end, discharging continuously through the other end.

contour: A line on a plan joining points of equal altitude.

contraflow: 1 Water flow in the opposite direction to that of the mineral being treated in a washer. 2 The direction of vibration of an inclined screen to retard the passage of material along the screen.

contraction joint: A break made in concrete work to allow for shrinkage during drying. Provision of these joints in long concrete structures prevents the formation of cracks.

control valve: In a hydraulic system, the valve which directs the flow of oil to operate the service in the direction required and connects the opposite service line to the reservoir.

controlled blasting: Techniques used to control overbreak and produce a competent final excavation wall. see ‘pre splitting and cushion blasting’.

conveyor: A mechanical device for transporting material in a continuous stream. The most common type of conveyor consists of a steel frame equipped with pulleys and idlers over which a continuous rubber belt travels loaded with material being moved from quarry to plant or within the plant.

conveyor system: A movable or stationary item of plant designed for the conveying of materials continuously from one location to another.

coolant: Material used to remove heat from an electrical device or equipment, eg air, hydrogen, oil and water.

co-ordinates: Rectangular co-ordinates are measured perpendicularly from axes which are at right-angles to each other. In surveying, the distances measured to the east are positive and called eastings or departures and those to the north are positive and called northings or latitudes.

copper loss: The heat energy loss in a conductor not intended to produce heat. This loss is proportional to the square of the current passing through the conductor and its resistance.

Cordtex: Detonating fuse.

core: 1 The cylindrical sample of rock bored out during core drilling. 2 The part of an electromagnetic circuit situated within the winding.

core-balance protection: A system of earth-fault protection applied to circuits in an ac electrical system having a neutral point earthed and utilizing a core-balance transformer to detect the earthleakage current.

core-balance transformer: A form of current transformer, the primary windings of which are connected in each phase of a circuit. The flux resulting from an out-of-balance current in the primary winding induces a voltage in a secondary winding.

core barrel: A length of pipe immediately above the bit of a rotary core drill. Double-core barrels have an inner portion mounted on a bearing so that it remains stationary and does not damage the core to the same extent when drilling is in weak friable strata.

core box: A long wooden box divided into sections wide enough to accommodate the cores taken from a borehole in the order they are removed for retention/examination.

core drilling: A method of rotary drilling in which a core is recovered.

core lifter: A spring clip at the base of the core barrel which grips the core, allowing it to be broken off and brought out of the hole.

core loss: see ‘iron loss’.

cost-plus: A form of contract used for urgent work by which the client pays for on-site labour, materials and plant costs plus an agreed sum to cover the contractor’s overheads and profit.

coulomb: The quantity of electricity transported in one second by a current of one ampere. Symbol: C.

counterbalance valves: Hydraulic pressure-maintaining valves used to prevent a load causing a cylinder to move faster than under the influence of pump flow.

country rock: The rock adjacent to a mineral vein or igneous intrusion.

couple: A pair of equal and opposite parallel forces which act upon a single structural member or element of a machine, but not in the same straight line.

coupling: The degree to which an explosive fills the hole. Bulkloaded explosives are completely coupled, untamped explosives are decoupled.

cover: The thickness of concrete between the steel reinforcement and the nearest face of the concrete. Insufficient cover may lead to corrosion of the reinforcement.

crash box: A hopper into which the material discharged from a crusher is deposited and from which it is removed by means of a feeder. This ensures that velocity is removed from the material which is then conveyed to the next stage at a controlled rate.

Cretaceous: The final period of the Mesozoic era (144-65 million years ago).

crimping: The action of squeezing the open end of a plain detonator, or a detonating relay, over a length of fuse.

critical diameter: The mimimum diameter of an explosive for propogation of a stable detonation. Critical diameter is affected by confinement, temperature and pressure on the explosive.

critical path: In network analysis the critical path is the path through the network that consists of the sum of the longest times, ie it determines the total time for the project and the completion date. It is represented by a bold line on the network.

cross-bedding: Laminations, in a bed of sedimentary rock, which are inclined to the general stratification.

cross bit: see ‘cruciform bit’.

cross-ply: Term applied to tyres having a number of casing plies, set one on another, running diagonally from bead to bead, each ply crossing the one immediately below it. This type of tyre has relatively stiff sidewalls.

crowd: Term describing the action of an excavator bucket being forced into the rock-pile.

crowd shovel: see ‘faceshovel’.

crown: 1 The part of a drill bit which contains the cutting diamonds. 2 The highest portion of the cross-section of a cambered carriageway.

Crown minerals: Minerals such as gold, coal, minerals on the sea bed etc ownership of which is vested in the Crown and may only be worked under licence issued by the Crown Estates Commissioners.

crown wheel: The larger wheel of a bevel reduction gear.

cruciform bit: A percussive bit having two cutting edges intersecting at right-angles.

crusher-run: Crusher product which has not been subjected to any subsequent screening.

crushing rolls: see ‘roll crushers’.

cube test: Test of the compressive strength of concrete cubes which have been cast and cured under standard conditions as detailed in BS 1881:Part 116.

cuber: Part of an automated concrete block-making system which stacks blocks ready for packaging.

cumulative curve: Any curve expressing the results of combining successive relative density fractions or size fractions.

curing: The process of preventing the loss of moisture from concrete while maintaininng a satisfactory temperature until it has developed the necessary degree of impermeability and strength.

current: A movement of electric charge. The direction of a current is taken as being that of the positive charges. Symbol:A. Unit:ampere.

current assets: Assets which will be owned for only a short period, usually less than a year from the date of the balance sheet, eg the value of stocks and stores, work in progress and the bank balance.

current liabilities: Liabilities which, it is expected, will be paid off within 12 months of the date of the balance sheet, eg outstanding suppliers’ accounts, bank overdrafts, tax liabilities etc.

current rating: 1 The current rating of a fuse is that current, less than the minimum fusing current, stated by the manufacturer as the current that the fuse link will carry continuously without deterioration, in accordance with relevant clauses of specification. 2 The safe working current of a conductor, eg a cable.

current transformer: An instrument transformer. The primary winding of the transformer is connected in series with the load and the lower current induced in the secondary winding, across which is connected an ammeter, is proportional to that in the primary.

cushion blasting: A surface blasting technique used to produce competent slopes. The cushion holes, fired after the main charge, have a reduced spacing and employ decoupled charges.

cusum: A method of graphical presentation of the cumulative sums of two related sets of data. An example of its use is for monitoring the quality of ready-mixed concrete which allows variation of the cement content to maintain the compressive strength of a standard mix at the desired level.

cut and fill: A surface mining technique in which overburden is dumped to occupy the void created by the removal of the mineral.

cut-back bitumen: Bitumen whose viscosity has been reduced by the addition of a flux, usually a petroleum oil.

cut-off shot: A shot in a delay round in which the charge has been wholly or partially exposed to the atmosphere by reason of the detonation of an earlier shot in the round.

cut stone: Stone chiselled into a desired shape.

cycle: The repetition of a variable quantity recurring in equal intervals of time.

cycle of operations: A series of several separate operations in a system of quarrying carried out in a predetermined order.

cyclone: A conical classifying device into which pulp is fed so as to take a circular path. Coarser and denser fractions of solids report to the apex of the cone, while finer particles overflow from the central vortex. Cyclones are also used for dewatering and in the removal of dust particles from air and other gases.

cyclone dust collector: An apparatus for the separation by centrifugal means of fine particles suspended in air or gas.

cyclone dust separator: A cone shaped air-cleaner which removes dust from air by centrifugal separation; a rapid vortex motion is applied to the air stream, causing dust to be thrown radially to the sides of the chamber.