GATE MN flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

RQD definition

Rock Quality Designation equals the sum of lengths of core pieces 100 mm or longer divided by total core run length, expressed as a percentage; it indexes rock mass fracturing.

Hoek-Brown criterion

Empirical rock mass failure criterion relating major and minor principal stresses through intact rock strength, geological strength index and disturbance factor, used for underground and slope design.

RMR rating ranges

Rock Mass Rating sums ratings for uniaxial compressive strength, RQD, discontinuity spacing, discontinuity condition and groundwater, adjusted for orientation; 81–100 very good down to below 21 very poor.

Q-system equation

Tunnelling quality index Q = (RQD/Jn) × (Jr/Ja) × (Jw/SRF), combining block size and shear strength ratios with water and stress reduction factors to select support.

Atkinson ventilation equation

Mine airway pressure loss p = k·L·P·Q²/A³, where k is friction factor, L length, P perimeter, Q airflow and A cross-sectional area; used to compute mine resistance.

Fan laws

For a fixed fan and system, airflow varies directly with speed, pressure with speed squared, and power with speed cubed; used to predict fan performance at changed speeds.

Methane explosive range

Methane in air is explosive between about 5% and 15% by volume, with the most violent explosion near 9.5%; ignition sources must be excluded from such atmospheres.

Powder factor

Powder factor is the mass of explosive used divided by the volume or tonnage of rock broken, expressed in kg/m³ or kg/t; it indicates blasting economy.

Scaled distance vibration

Peak particle velocity from blasting is predicted as v = K·(D/√Q)^−b, where D is distance, Q maximum charge per delay, and K, b are site constants.

ANFO characteristics

Ammonium nitrate fuel oil is a low-cost dry-hole explosive with moderate velocity and strength; it loses performance in water and produces fumes requiring ventilation.

Bond comminution law

Bond's law states W = 10·Wi·(1/√P80 − 1/√F80), where W is specific energy, Wi work index, and F80, P80 are feed and product 80% passing sizes in micrometres.

Two-product formula

Concentrate grade is calculated from feed, concentrate and tailings assays using mass balance; recovery is concentrate mass times grade divided by feed mass times grade.

Flotation reagents

Collectors adsorb on mineral surfaces to make them hydrophobic, frothers stabilise bubbles, and depressants or activators modify selectivity; pH controls sulphide flotation.

Tromp curve

A gravity separation performance curve plotting the fraction of each density fraction reporting to the concentrate against density; the probable error measures separation sharpness.

Stripping ratio

Stripping ratio is the volume or mass of waste removed per unit of ore mined; it determines surface mining cost and the economic pit limit.

Block caving method

An underground mass mining method where undercutting causes the orebody to cave under gravity; ore is drawn from drawpoints, requiring careful dilution control.

Longwall mining

A high-production underground coal method using a long face between two gates, with powered supports and a shearer; the roof is allowed to cave behind the supports.

Lerchs-Grossmann algorithm

A graph-theoretic optimisation method that determines the ultimate pit limit maximising undiscounted pit value subject to slope angle constraints.

Cut-off grade

The minimum grade at which material is economically worth mining and processing, balancing mining, processing and refining costs against metal price and recovery.

Net present value

NPV discounts all project cash flows at a chosen rate and subtracts initial capital; a positive NPV indicates the project adds value at that discount rate.

Injury frequency rate

Frequency rate equals the number of reportable injuries multiplied by one million and divided by man-hours worked; it standardises safety comparison across operations.

Bowditch traverse adjustment

Compass rule distributes traverse closure error in proportion to leg length, correcting latitudes and departures so the traverse closes on the known point.

Gyrotheodolite orientation

A gyrotheodolite determines true north underground by sensing earth rotation, transferring surface azimuth to underground workings where shafts prevent direct sighting.

Conveyor capacity

Belt conveyor capacity equals material cross-section on the belt multiplied by belt speed and bulk density, adjusted for surcharge angle and idler troughing.

Hoisting rope safety factor

The ratio of rope breaking strength to maximum static load including conveyance and rope weight; statutory minimum values apply to winding and guide ropes.

Kirsch solution

Elastic stress distribution around a circular opening in a biaxial stress field; tangential boundary stress reaches three times the major principal stress minus the minor.

Subsidence angle of draw

The angle between the vertical at the extraction boundary and the line to the surface point of zero subsidence; it defines the surface influence zone.

Slope factor of safety

Factor of safety equals resisting shear strength divided by driving shear stress along a potential failure surface; values near one indicate marginal stability.

Smooth blasting

A controlled blasting technique using closely spaced, lightly charged perimeter holes fired after the main blast to create a clean final wall and reduce overbreak.

Misfire procedure

When a charge fails to detonate, the area is evacuated and marked; the hole is never redrilled, and the charge is removed or destroyed per approved site procedure.

Spontaneous combustion

Self-heating of coal by low-temperature oxidation; detected by carbon monoxide ratios and temperature, controlled by sealing, inert gas and stowing.

Hydrocyclone cut size

The particle size at which half the feed reports to overflow and half to underflow; it decreases with smaller cyclone diameter and higher pressure.