B — Dictionary of Quarrying Terms

BACMI: abbr. British Aggregate Construction Materials Industries. A former trade association for producers of aggregates, ready mixed concrete, lime and coated materials which amalgamated with SAGA to create QPA.

BCA: abbr. British Cement Association. The trade association for cement manufacturers in the UK.

back-acter: A shovel which digs towards the Back acter machine and is capable of digging below track level.

back breakage: The extent of rock breakage or fracture behind the burden taken in a blast.

back emf: Voltage induced in a circuit which opposes the applied voltage, eg in the armature of a dc motor as it rotates in its magnetic field.

backfill: Overburden or inferior mineral which is dumped into a worked out part of an excavation or behind a retaining wall.

backhoe loader: Self-propelled wheeled machine with a main structural support designed to carry both a front-mounted bucket loading mechanism and a rear-mounted backhoe. When used in the backhoe mode, the machine normally digs below ground level with the bucket motion towards the machine; the backhoe lifts, swings and discharges the material while the undercarriage is stationary.

backsight: In surveying, a sight taken towards the previous station.

bag filter: An apparatus for removing dust from dust-laden air, employing a container made from woven material which permits passage of air but retains solid particles.

bailer: A tube, fitted with a valve at its base, which is lowered into a borehole to remove cuttings and water.

balance sheet: A statement showing a company’s assets and liabilities at one moment in time, that is the close of business on the date shown. All registered limited companies are, by law, required each calendar year to prepare and publish a balance sheet for the shareholders’ information and it must be presented in an approved format.

balanced load: Symmetrical arrangements of loads in an electrical system. Loads are balanced in an ac three-phase system when the loads taken from each phase are equal and at the same power factor.

ball bearing: A bearing consisting of a number of hardened steel balls which roll between an inner race fitted on to the journal and an outer race held in a housing. The inner and outer races carry shallow spherical tracks on their outer and inner surfaces respectively and a cage between the races keeps the rolling elements separate and evenly spaced.

ball deck: A coarse mesh secured below the screen surfaces, the area between the two meshes being divided into compartments each of which contains a number of hard rubber balls. With the movement of the screen, the balls bounce freely within their compartments and assist in preventing blinding or pegging of the screen mat.

ball mill: A grinding machine consisting of a short, horizontal cylinder charged with steel balls which break down the mineral during rotation.

ballasted tyres: Tyres filled with liquid or dry ballast in order to increase their weight when fitted to the wheels of tractors, graders, wheeled dozers etc. This, it is claimed, results in increased operating efficiency.

banana screen: A multi-slope vibrating screen. The angle of the deck decreases from feed end to discharge end.

bank of cells: A row of flotation cells in line.

bar: Unit of pressure equal to 100,000 newtons/m² or Pascals. Standard atmospheric pressure = 1.0133 bar.

bar screen: A stationary inclined screen, comprising longitudinal bars, spaced at intervals, on to which the material to be screened is fed at the upper end.

barrel washer: see ‘washing barrel’.

barytes: Barium sulphate, BaS0₄. A dense mineral (RD 4.5) used in the manufacture of paint, textiles and drilling mud, and as an aggregate in radiation shielding. Can be an undesirable impurity in limestone.

basalt: A fine-grained basic igneous rock occurring in dykes, sills and lava-flows; essential minerals are plagioclase felspar and augite. Dark grey to black in colour; relative density 2.8-3.3; aggregate crushing value 7-25.

base charge: 1 The detonating component in a detonator initiated by the priming charge. 2 The bottom charge in a deep blasthole.

base line: An accurately measured line which forms one side of the first triangle in a triangulation survey.

basecourse: 1 The European term for the layer(s) that form the main structural element of the road. 2 An obsolete British term for the European term, binder course, which forms part of the road immediately below the surface course.

basic work content: The minimum time, at a standard rate of working, in which a task can be completed if everything is carried out perfectly.

basin: A rock structure in which the strata dip inwards on all sides.

batch-heater plant: A heating and mixing plant particularly suited to the production of a range of coated materials.

batch mixer: A mixer for bituminous or concrete materials which mixes batches of such materials, as opposed to continuous mixers.

batching plant: A plant containing the equipment to measure, by weight or volume, the quantities of different materials required to make a correct mix of concrete.

batholith: A large and, originally, deap-seated igneous intrusion. See ‘dyke’.

batter: A constructed, uniform, steep slope. The inclination to the vertical of such a slope is expressed as one unit horizontally to so many units vertically.

battery: An assembly of similar units.

Baum jig: A jig used for separating coal from shale in which a pulsating motion is given to the water by intermittent admission of compressed air to the wash-box.

beam compasses: An instrument used to draw arcs of larger radius than are possible with ordinary compasses. It consists of a beam of metal or wood carrying two adjustable heads which take a point and a pen or pencil.

bearing: 1 The horizontal angle between a datum direction such as north and a given line. 2 Device provided to support and hold a revolving shaft in the correct position.

bed: A layer of rock or mineral.

bedding: A formation of distinct sedimentary rock layers or beds one upon another.

bedding plane: The interface between two adjacent beds of sedimentary rock.

bedplate: A cast-iron plate or steel frame on which a machine is mounted; it is usually bolted to the floor.

bedrock: The solid rock underlying superficial deposits

behavioural science: A study in man management based on motivation theory.

belt feeder: A short endless belt conveyor for feeding material, for example, from a bunker.

bench mark: A point of known elevation above Ordnance datum which has been established by the Ordnance Survey. abbr: BM.

benches: The long horizontal levels or steps to which successive quarry faces are taken and along which mineral, stone or overburden is worked.

benching: A method of working opencast pits or quarries in benches usually using rows of blastholes drilled parallel to the face.

bending moment: At a given section of a beam, the bending moment is equal to the algebraic sum of the moments of all the forces to either side of the section.

beneficiation: The processing of rocks and minerals to remove unwanted constituents, ie improve their quality.

berm: An embankment usually constructed from earth or overburden to form a safety barrier.

Bernoulli’s law: The total kinetic, potential and pressure energy per unit volume of a fluid passing through a system is constant at all points in that system.

bevel gear: A system of toothed wheels which connect shafts that are at an angle to each other but in the same plane.

bimetal: Two or more metals, having different coefficients of expansion, bonded together to form a temperature-sensitive device. A change in the temperature of a bimetallic strip results in a change of curvature and this is utilized in electrical indicating instruments and safety devices.

binder: 1 Bitumen used to cement aggregate particles or to stick chippings to a road surface. 2 Any cementing agent used for binding soil or aggregate.

binder course: The European term for the course immediately below the surface course in a flexible road construction.

biotite: A dark-coloured iron-bearing member of the mica group of rock-forming minerals. It occurs as a constituent of many igneous and metamorphic rocks.

bit: 1 A cutting tool which is detachable from the drill rod. 2 The end of a drill stem that forms the actual cutting edge.

bitumen: A viscous liquid or solid consisting of hydrocarbons and their derivatives. It is soluble in carbon disulphide, substantially non-volatile and softens gradually when heated. It is black or brown in colour and has waterproofmg and adhesive properties. It is derived from petroleum or from naturally occurring asphalt.

bituminous: Containing, or mixtures of, road tar, bitumen or pitch.

black powder: A low explosive composed of sodium or potassium nitrate, charcoal and sulphur.

Blake crusher: Double-toggle jaw crusher originally designed in 1858 by E.W. Blake.

blast: The detonation of explosives to break rock.

blast area: The area near a blast within the influence of flying rock missiles or concussion.

blasthole: A hole drilled in rock or other material for the placement of explosives.

blasting agent: A primer sensitive explosive such as ANFO.

blasting gelatine: A high explosive; the most powerful commercial explosive, taken as the standard of explosive power.

blasting ratio: The ratio of the yield of material from a blast to the weight of explosives used; measured in tonnes/kg.

bleeding: 1 Separation of water from concrete after compaction when there is a tendency for the solids to settle and the displaced water to be pushed to the surface. 2 The occurrence of free bitumen from an over-rich load of coated material in transit or on the road.

blinding: 1 The blocking of screen apertures by the agglomeration of damp fine material, this results in a reduction of the effective area of the screen. 2 The application of fine material to a surface to reduce the surface voids or to cover a bituminous binder.

blow-bars: The replaceable hammers rigidly attached to the rotor of an impact crusher.

blown-out shot: A shot which has expended its force outwards from the line of the shothole without doing any appreciable blasting work.

bolted-plate fastener: A type of conveyor belt fastener which consists basically of pairs of steel plates which are used to clamp the ends of the belt together. The plates may be in two halves connected by hinge pins.

Bond’s third theory: A comminution theory concerned with the energy required to reduce a given size of feed to a required size of product. On his theory F.C. Bond based an empirical formula which may be used to compare the efficiencies of crushing plants etc.

boning rod: A T-shaped staff used with other similar staffs to furnish a line of sight whereby, from two given points, other points at the same level or on the same gradient can be established.

booking: In surveying, the recording of field observations in such a way that they can be understood, often by someone else, when later used in the field or office.

boom: A cantilever structure: 1 attached to lifting or excavating equipment and at the outer end of which is fixed the pulley over which the hoist rope passes 2 carrying a conveyor used to feed a stockpile.

booster: A unit of explosive or blasting agent used for perpetuating or intensifying an explosive reaction.

borehole logging: The determination of physical, electrical and radioactive properties of the rocks traversed by a borehole.

borrow pit: Excavation adjacent to major works site to provide construction materials.

boss: A circular form of igneous intrusion; a small-scale batholith.

bottom initiation: see ‘inverse initiation’.

boulder clay: Glacial clay, generally containing a variety of boulders or pebbles.

Bow’s notation: A method of notation for forces acting at a point; the spaces between the forces within the structure are lettered in order, so that each force is identified by means of the two letters in the spaces on either side of it. By this device vector diagrams can be lettered correspondingly.

bowl scraper:A load-haul-dump machine in which the bowl is towed behind a tractor unit, fills by a planing action, hauls the spoil to the dump site and empties by means of an internal ejector blade pushing forward. Used in soft ground or in ground that fragments well after ripping or blasting.

box cut: The initial opening to establish a working face for open-pit mining,

brass: An alloy of copper and zinc, but small amounts of elements such as aluminium, iron, lead, manganese and nickel are frequently added to give increased strength and other mechanical properties. Brasses can be readily machined.

break point: 1 The instant at which one element in a work cycle ends and another begins. 2 The point at which a bitumen emulsion moves out of its aqueous phase as part of its setting process. Usually accompanied by a change of colour from brown to black.

breakout force: The force with which an excavator is capable of pushing its bucket through the rockpile or face.

breast hole: A horizontal or near-horizontal blasthole used to create or improve a quarry floor.

breccia: A rock consisting of broken angular unworn fragments held together by a natural cement.

brick paving: A surface composed of bricks laid in a regular pattern on a prepared roadbase.

bridge wire: A very fine filament wire embedded in the ignition element of an electric detonator. An electric current passing through the wire causes a sudden temperature rise resulting in the ignition element being ignited.

British Standard: A numbered publication of the British Standards Institution describing the quality or dimensions of a product, and methods of testing. By their use in specifications architects and engineers can reduce the length of their descriptions to a reference, eg BS 4483 : 1985. Specification for steel fabric for the reinforcement of concrete.

bronze: True bronzes are alloys of copper and tin, but the name is now applied to other alloys not containing tin, eg aluminium bronze. Various types of bronze are used for springs, bushes, bearings, valve bodies etc.

brush: A conductor used to make electrical contact between a stationary and a moving surface.

bucket-chain excavator: A continuous-feed machine designed to give a high output of soft material using a chain of buckets and essentially designed for digging below grade.

bucket elevator: A continuous line of buckets attached by pins to two endless chains running over tracks and driven by sprockets; alternatively, the buckets are attached to a rubber belt. Used for raising loose materials or slurries at high angles or vertically.

bucket-wheel excavator: A continuous-feed machine, usually carried on crawler tracks, consisting essentially of a large cutting wheel with buckets mounted on the periphery.

bucket-ladder dredge: A dredge having buckets moving in a continuous chain, reaching down into the deposit to be dredged, and lifting it for discharge into the vessel.

budgetary control: A costing and cost-control technique by which the management of a company, having set out to anticipate their volume of trading and consequent production costs for a given period in the future, compares actual performance with budget.

buffer blasting: Face blasting, either against a high unexcavated rock pile, or using an increased burden (usually 1.5 times or twice the normal burden).

bulk density: The density of a material including any voids and water contained in it.

bulk mix: A mass of explosive material prepared for use without packaging.

bulk strength: The strength of explosive per unit of volume expressed as a percentage of the value of blasting gelatine or ANFO as standard.

bulldog clip: A V-bolt specially designed to clamp a steel-wire rope doubled back on itself.

bulldozer: A high-powered caterpillar-mounted tractor fitted with a concave blade mounted in front of the machine. Used for smoothing out irregularities in working areas, levelling the tops of dumps, clearing spillage etc.

bund: An earth mound or embankment.

bunker: A storage bin for stone, coal etc.

burden: The distance between an explosive charge and the nearest free face which is a measure of the work to be done by the charge.

burner: The heater unit used in coating plants for raising the temperature of aggregate prior to mixing with the bitumen. Fuel may be gas oil, waste oil, gas or coal.

bursting time: The total time interval between the application of current to an instantaneous detonator and its explosion.

busbar: An equipotential conductor forming a terminal or junction point in a power system, for the connection of supplies and feeders.

butt weld: A weld between two pieces of metal without any overlap between them.

button bit: A percussive drill bit having tungsten carbide inserts the hemispherical ends of which protrude from the face of the bit.

byte: The unit used in describing the memory capacity of a computer (1 Mbyte = million characters).