| dB |
| Decibels is a measure of sound pressure expressed on a logarithmic scale relative to the lowest sound the human ear can detect (P0 = 2 x 10-5 Pa) and is given as dB = 20 log10(P/P0) where P is the pressure in Pascals. The response of the ear to sound levels is logarithmic with a change of 1dB being the same perceived change at any level. A 1dB change is only perceivable under controlled conditions. |
| dB(A) |
| This is short for decibel(A-weighting). It is a measure of sound pressure which has been weighted to reflect the way that a human ear responds. |
| dB(Lin) |
| This is short for decibel(Linear) but is often abbreviated to dB. It is the name given to the absolute measure of pressure, to differentiate it from weighted measures such as dB(A), which is modified to reflect the way a human ear responds. As it is the real air overpressure which may cause damage from a blast, it is the dB(Lin) which is measured and recorded. |
| DCLG |
| See Department for Communities and Local Government. |
| Decibels |
| Decibels is a measure of sound pressure expressed on a logarithmic scale relative to the lowest sound the human ear can detect (P0 = 2 x 10-5 Pa) and is given as dB = 20 log10(P/P0) where P is the pressure in Pascals. The response of the ear to sound levels is logarithmic with a change of 1dB being the same perceived change at any level. A 1dB change is only perceivable under controlled conditions. |
| Decked Charge (decking) |
A blast borehole is deck charged when the explosive column is divided into 2 or more separate units, divided by drill material or air bags which form the decking. These separate units can be fired on different delays to reduce the MIC.
 Click to enlarge. |
| Defra |
| See Department for Environment, Food and Rural Affairs. |
| Density |
| Mass of rock per unit volume. It is usually expressed as tonnes per cubic metre or as a ratio of mass to volume expressed as specific gravity (SG). Most rock density or SG is in the range of 2.0 (sand) to 3.0 (basalt) tonnes per cubic metre. |
| Department for Communities and Local Government (DCLG) |
| Department for Communities and Local Government. This UK Government Department took over responsibility for planning issues from the Office of the Deputy Prime Minister in May 2006. |
| Department for Environment, Food and Rural Affairs (Defra) |
| Department for Environment, Food and Rural Affairs. This is a government department whose aim is sustainable development. www.defra.gov.uk |
| Deposit Gauge |
| An instrument used to measure the rate of deposition of particulate matter, such as that specified by BS 1747 (Part 1). There are many designs of gauge, and they may also be known as dust gauges. |
| Deposition |
| The process by which airborne dust falls from atmospheric suspension, returning to surface as deposited dust. |
| Desk-based Appraisal |
| A rapid assessment of the readily available records to ascertain whether the proposed extraction has potential archaeological implications. |
| Desk-based Assessment |
| A thorough review of all available archaeological and historical information relating to the proposal area and its environs, sufficient to form the ?heritage? element of an EIA. |
| Dessication |
| A complete drying out. |
| Detonator |
| Device for initiating main explosive charge during blasting. Both electric and non-electric detonators can be used. |
| Development Control |
| These are the procedures that operate to ensure that the decision about whether to permit a particuar mineral application is made in the appropriate way. |
| Development Plan |
| A set of documents (text and maps) which contain the regional planning body and local planning authority policies and proposals for development, including minerals (Regional Spatial Strategies and Development Plan Documents). Unitary development plans, structure plans and local plans are now superseded. |
| Development Plan Documents (DPD) |
| Development plan documents, together with the Regional Spatial Strategy, form the development plan. The DPD include the core strategy, allocations, proposals map and action area plans. |
| Dewatering |
| The removal of surface and groundwater from the mining area and surrounds prior to, and during, mining and quarrying operations. It also applies to removal of water from a product. See drying. |
| Digging |
| The extraction of material (mineral or overburden) by machine. |
| Discharge consent |
| Discharge consents are required for a variety of materials being discharged into controlled waters. Controlled waters include all inland watercourses, estuaries, coastal waters and groundwater, under the Water Resources Act 1991, but its requirements may be incorporated in an IPC or IPPC Authorisation, or Waste Management Licence. |
| Discing |
| A technique for breaking up the ground using circular discs behind a tractor
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| Dispersion |
| The atmospheric movement of suspended matter away from the source of the emissions. |
| Displacement |
| The amount of movement measured in metres (m) in metric. Displacement of the ground is hard to measure for ground vibration as there is no stable reference point against which to measure the movement. |
| Do nothing scenario |
| Continued change or evolution of landscape or environment in the absence of the proposed development. |
| DoE |
| Department of the Environment. This was the government department responsible for all aspects of the physical environment in England, Scotland and Wales. This has now been superseded by DEFRA. |
| Double toggle jaw crusher |
| Jaw crusher where the moving jaw is hung from a non-eccentric pivot, and therefore has a simple lateral motion. It has two toggle plates. |
| DPD |
| See Development Plan Documents |
| Dragline |
Large mobile excavator with a bucket suspended by steel rope from a long jib or boom. It is generally used for overburden or waste removal in large openpit mines, especially coal mines. They can be diesel or electric powered, usually with walking feet rather than caterpillar tracks due to their large size and weight. Bucket capacities may range from 30 to 60 m3, though examples have reached 165m3. It digs below the level of the machine.
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| Drainage Basin (catchment area, watershed) |
| A land area where precipitation runs off into streams, rivers, lakes, and reservoirs. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large drainage basins, like the area that drains into the River Severn contain thousands of smaller drainage basins. |
| Dredging |
| Excavation of materials from below water level in a flooded quarry or the bed of a river, lake or the sea bed. Dragline or bucketwheel excavators have been used, but suction techniques are now most common. |
| Drift |
| Surface material such as sand and gravels which often cover the bedrock underneath. They are usually unconsolidated or loose materials.
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| Drilling |
| Penetration of soil or rock by machine rotary or percussion drill for sampling or blasting operations |
| Dry screening |
| Separation of coarser and finer dry material by passing it over a vibrating metal plate, which has apertures of the desired size through which the finer (undersize) material falls. |
| Dry Silo mortar |
| An onsite silo containing a premixed mortar, or separate fine aggregate and cement, which is mixed to specification in the silo. It enables consistent quality and availability to be maintained in large construction operations. |
| Dry working |
| The operation of a quarry (particularly a sand and gravel quarry) above the water table. |
| Drying |
| The removal of water from a product by heating or use of a filter press. |
| DTI |
| Department of Trade and Industry. The Government office working to created the best environment for business success in the UK. www.dti.gov.uk. |
| Dust |
| BS 6069 (Part 2) defines dust as particulate matter less than 63 microns in diameter. Dust is also the generic term used to describe particulate matter which, although it may be found resting on the ground or other surfaces as solid matter, is capable of becoming airborne to disperse in the atmosphere prior to returning to surface. In construction work it can be applied to the 3mm (less than 3mm) rock product. The term is also used to describe larger particles resting on the ground or other surfaces that can become airborne to disperse in the air before returning to the surface. |
| Dynamic classifiers(centrifugal and/ or mechanical) |
| Machines that separate particles into size fractions by centrifugal force using air (most common) or water. The Dorr-Oliver mechanical classifier separates wet slimes from sand by using a mechanical rake in a tank with a sloping base to move the materials. |