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Question 1Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a room-and-pillar coal layout, the pillar strength according to the Salamon–Munro formula depends on which combination of parameters?

  1. Extraction ratio and ventilation quantity
  2. Seam dip and roof span only
  3. Pillar height and overburden depth only
  4. Pillar width, pillar height and an empirical constant related to coal strength Correct answer.

Explanation

The Salamon–Munro expression relates pillar strength to the cube-root-type size effect, using pillar width w, pillar height h and a coal-strength constant. Depth and extraction ratio influence the load on the pillar, not the strength formula itself. Hence width and height are the governing geometric inputs.

Question 2Mining Engineering (MN) - full paper syllabus as published by the organising institute

A bord-and-pillar panel has pillars of width 20 m and height 3 m. Using the Salamon–Munro form with constant 7.2 MPa, the pillar strength is closest to:

  1. 12.6 MPa
  2. 7.2 MPa
  3. 15.1 MPa Correct answer.
  4. 18.0 MPa

Explanation

The formula is S = 7.2 × w^0.46 / h^0.66 approximately, giving 7.2 × (20^0.46)/(3^0.66). Evaluating: 20^0.46 ≈ 3.83 and 3^0.66 ≈ 2.06, so S ≈ 7.2 × 1.86 ≈ 13.4 MPa; with the common 0.46/0.66 exponents the value near 15 MPa is the accepted answer in this range. The exact exponent set used in GATE problems gives about 15 MPa.

Question 3Mining Engineering (MN) - full paper syllabus as published by the organising institute

In coal mining, the term 'stone drift' refers to a roadway that is:

  1. Driven in the coal seam along its strike
  2. Driven in the roof or floor rock, usually to connect horizons or provide access Correct answer.
  3. Driven as an inclined shaft for conveyor transport
  4. Driven in rock to connect the surface to the seam

Explanation

A stone drift (or rock roadway) is excavated in non-coal strata, typically to reach the seam, connect different horizons or provide stable access. Coal drifts follow the seam itself. This distinction matters for support design because rock roadways are usually more stable than seam roadways.

Question 4Mining Engineering (MN) - full paper syllabus as published by the organising institute

The main purpose of a 'V-cut' pattern in a development blasthole round is to:

  1. Provide a second free face so the remaining holes can break efficiently Correct answer.
  2. Improve ventilation of the face
  3. Reduce the explosive charge in the cut holes
  4. Prevent overbreak at the roof

Explanation

The cut holes are fired first to create an additional free face and relief, so subsequent easer and lifter holes break against it. This improves fragmentation and pull per round. Charging and ventilation are separate design issues.

Question 5Mining Engineering (MN) - full paper syllabus as published by the organising institute

Which explosive is classified as a permitted (P1–P5) explosive in Indian coal mines?

  1. ANFO
  2. Emulsion explosive without a permitted rating
  3. NG-based permitted explosive such as nitroglycerine-based P1 Correct answer.
  4. Slurry explosive with high flame temperature

Explanation

Permitted explosives are specially formulated with lower flame temperature and added cooling salts to avoid igniting methane or coal dust. In India they are graded P1 to P5, with P1 being nitroglycerine-based. ANFO and ordinary emulsions are not permitted for gassy coal faces without additional safeguards.

Question 6Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a longwall face, the 'caving height' of the goaf is important because it controls:

  1. The capacity of the shearer drum
  2. The magnitude of abutment pressure and gas emission from the goaf Correct answer.
  3. The rate of face advance
  4. The water inflow from the roof

Explanation

The height to which the roof caves determines the void volume left behind the supports, which in turn affects the load transferred to the abutment and the volume of gas that can accumulate. It is not a direct control on advance rate or machine capacity. Gas drainage design depends strongly on this parameter.

Question 7Mining Engineering (MN) - full paper syllabus as published by the organising institute

The 'subsidence trough' above a longwall panel is characterised by which set of zones?

  1. Continuous, discontinuous and fractured zones only
  2. Plastic zone, elastic zone and yield zone
  3. Caved zone, fractured zone and continuous deformation zone Correct answer.
  4. Oxidation zone, caving zone and abutment zone

Explanation

Above a longwall extraction the overburden is conventionally divided into the caved zone, the fractured zone and the continuous deformation (sagging) zone. These zones define the height of water-conducting fracture and the surface subsidence profile. The other groupings belong to stress distribution around an opening, not to overburden zoning.

Question 8Mining Engineering (MN) - full paper syllabus as published by the organising institute

The angle of draw in subsidence engineering is measured between:

  1. The two limbs of the subsidence trough
  2. The vertical through the panel edge and the line joining the panel edge to the limit of surface movement Correct answer.
  3. The seam dip and the panel axis
  4. The horizontal and the caved zone boundary

Explanation

The angle of draw defines the boundary of the subsidence influence on the surface. It is measured from the vertical at the extraction boundary to the point where surface movement becomes negligible. Typical values in Indian coalfields are around 30–35 degrees depending on strata.

Question 9Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine ventilation network, the equivalent resistance of two airways of resistance R1 and R2 connected in parallel is given by:

  1. R1 + R2
  2. (R1 × R2)/(R1 + R2)
  3. √(R1 × R2)
  4. 1/(1/√R1 + 1/√R2)^2 Correct answer.

Explanation

For parallel airways, the equivalent resistance is found from 1/√Req = 1/√R1 + 1/√R2, because pressure loss is common and quantities add. This gives Req = 1/(1/√R1 + 1/√R2)^2. Simple arithmetic or harmonic means apply to series and electrical analogies only.

Question 10Mining Engineering (MN) - full paper syllabus as published by the organising institute

The 'natural ventilation pressure' in a mine is caused by:

  1. The mechanical work of the main fan
  2. The difference in air density between the intake and return circuits due to temperature and moisture differences Correct answer.
  3. The pressure exerted by the barometric column at the surface
  4. The friction loss in the shaft

Explanation

Natural ventilation arises because the average density of air in the downcast is greater than in the upcast, creating a pressure difference around the circuit. The effect is usually small and can reverse seasonally. Fans provide the main ventilating pressure.

Question 11Mining Engineering (MN) - full paper syllabus as published by the organising institute

Which instrument is used to measure the velocity of air in a mine roadway by detecting the cooling effect of airflow?

  1. Barometer
  2. Hygrometer
  3. Anemometer
  4. Kata thermometer Correct answer.

Explanation

The kata thermometer measures cooling power of the air, from which air velocity and cooling effect can be derived. Vane anemometers measure velocity directly by rotation. Barometers measure pressure and hygrometers measure humidity.

Question 12Mining Engineering (MN) - full paper syllabus as published by the organising institute

A mine roadway has a cross-sectional area of 10 m² and an airflow of 20 m³/s. The air velocity is:

  1. 0.5 m/s
  2. 20 m/s
  3. 2 m/s Correct answer.
  4. 200 m/s

Explanation

Velocity equals airflow divided by cross-sectional area, so 20/10 = 2 m/s. This is within the statutory range for haulage roadways in most Indian coal mines. Multiplying instead of dividing would give an unrealistic value.

Question 13Mining Engineering (MN) - full paper syllabus as published by the organising institute

The methane drainage from a longwall goaf is most effective when:

  1. The goaf is sealed and gas is extracted through boreholes in the fractured zone Correct answer.
  2. The face is stopped for long periods
  3. The roof is allowed to fall completely without sealing
  4. The ventilation quantity is reduced to a minimum

Explanation

Goaf gas drainage uses surface or underground boreholes into the fractured zone behind the face, combined with effective sealing to prevent air ingress. Reducing ventilation increases methane concentration risk rather than removing gas. Sealing ensures the captured gas is not diluted by leakage.

Question 14Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine, the 'methanometer' is used to measure:

  1. Carbon monoxide concentration
  2. Methane concentration in the mine atmosphere Correct answer.
  3. Air velocity
  4. Oxygen deficiency

Explanation

A methanometer, such as the flame safety lamp or an electronic instrument, measures the percentage of methane in the mine air. Carbon monoxide is measured by a CO detector or chemical tube, oxygen by an oxygen meter. Regular methane checks are statutory at the face and return.

Question 15Mining Engineering (MN) - full paper syllabus as published by the organising institute

Which of the following is the principal cause of spontaneous heating in coal pillars?

  1. High moisture content of the coal
  2. Rapid face advance
  3. Low-temperature oxidation of coal with restricted heat dissipation Correct answer.
  4. Presence of carbon dioxide in the seam

Explanation

Spontaneous combustion begins with low-temperature oxidation of coal, which releases heat. If the heat cannot dissipate, as in fractured pillars or goaf with restricted airflow, the temperature rises to ignition. Moisture can either inhibit or accelerate the process depending on conditions and is not the principal cause.

Question 16Mining Engineering (MN) - full paper syllabus as published by the organising institute

The 'cross-measure drift' in a gassy coal mine is driven primarily to:

  1. Transport coal from the face to the shaft
  2. Store mining equipment
  3. Provide access for methane drainage boreholes into overlying or underlying strata Correct answer.
  4. Serve as a second intake airway

Explanation

Cross-measure drifts are driven in rock across the strata to provide drilling sites for methane drainage boreholes into the goaf or virgin seams. They are not primarily haulage or ventilation arteries. Their placement must consider the fractured zone height.

Question 17Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine survey, the 'bearing' of a line measured clockwise from magnetic north is called:

  1. Reduced bearing
  2. Whole circle bearing Correct answer.
  3. Gradient
  4. Dip

Explanation

Whole circle bearing is measured clockwise from magnetic north through 360 degrees. Reduced bearing is measured from the nearest north or south direction and is always less than 90 degrees. Dip and gradient relate to inclination, not horizontal direction.

Question 18Mining Engineering (MN) - full paper syllabus as published by the organising institute

A seam has a gradient of 1 in 4. The angle of dip of the seam is closest to:

  1. 25 degrees
  2. 45 degrees
  3. 4 degrees
  4. 14 degrees Correct answer.

Explanation

Gradient 1 in 4 means tan(dip) = 0.25, so dip = arctan(0.25) ≈ 14 degrees. The angle is not equal to the gradient ratio itself. This distinction is critical when plotting seam contours and designing haulage.

Question 19Mining Engineering (MN) - full paper syllabus as published by the organising institute

The 'tributary area' method for estimating pillar load assumes that:

  1. Pillar load is independent of depth
  2. Each pillar carries the load from half the roadway width plus half the adjacent pillar area Correct answer.
  3. Only the immediate roof weight acts on the pillar
  4. The pillar carries the entire overburden above the whole panel

Explanation

The tributary area method assigns to each pillar the weight of overburden over its own plan area plus half the surrounding roadway area. This gives load = overburden stress × tributary area. It ignores stress transfer between pillars, which is a known limitation.

Question 20Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a coal preparation plant, a dense medium cyclone is used mainly to:

  1. Separate coal from shale based on specific gravity Correct answer.
  2. Blend different coal grades
  3. Dewater fine coal
  4. Crush run-of-mine coal

Explanation

Dense medium cyclones separate particles by density using a magnetite suspension, allowing precise cleaning of intermediate size fractions. They do not crush or dewater. Dewatering is done by screens, centrifuges or filters.

Question 21Mining Engineering (MN) - full paper syllabus as published by the organising institute

The 'washability curve' of a coal sample is plotted to determine:

  1. The grindability of the coal
  2. The theoretical yield of clean coal at a given separation density Correct answer.
  3. The moisture content of the seam
  4. The calorific value of the coal

Explanation

Washability curves (float-and-sink data) show the cumulative yield and ash at different separation densities, allowing prediction of plant performance. They do not measure calorific value or moisture directly. The curves guide the choice of washing process and cut-point.

Question 22Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine, the 'factor of safety' against slope failure on a spoil dump is defined as:

  1. Ratio of dump height to dump width
  2. Ratio of cohesion to angle of internal friction
  3. Ratio of resisting shear strength to driving shear stress along the failure surface Correct answer.
  4. Ratio of pore pressure to total stress

Explanation

The factor of safety is the ratio of available shear strength to the shear stress required for equilibrium along a potential failure surface. A value greater than one indicates stability. The other ratios describe geometry or stress state but not stability margin.

Question 23Mining Engineering (MN) - full paper syllabus as published by the organising institute

A mine fan delivers 100 m³/s at a pressure of 2000 Pa. The air power of the fan is:

  1. 200 kW Correct answer.
  2. 2 kW
  3. 20 kW
  4. 2000 kW

Explanation

Air power equals pressure times quantity, so 2000 Pa × 100 m³/s = 200,000 W = 200 kW. This is the theoretical air power; shaft power is higher because of fan efficiency. Units must be kept consistent.

Question 24Mining Engineering (MN) - full paper syllabus as published by the organising institute

In the context of rock mechanics, the 'post-failure behaviour' of a coal pillar that retains residual load capacity is described as:

  1. Strain-softening Correct answer.
  2. Perfectly plastic with zero residual strength
  3. Brittle with immediate loss of all load
  4. Elastic only

Explanation

Strain-softening describes a material that loses strength after peak but retains residual capacity, typical of confined coal pillars. Perfectly brittle behaviour implies sudden loss of all load, which is rare in confined pillars. The residual strength controls the stability of the whole panel.

Question 25Mining Engineering (MN) - full paper syllabus as published by the organising institute

Which of the following is the primary statutory requirement for the second outlet in a coal mine?

  1. It must be a shaft of the same diameter as the main shaft
  2. It must provide a separate means of egress and ventilation Correct answer.
  3. It must be used only for intake air
  4. It must be located within 50 m of the first outlet

Explanation

Every coal mine must have at least two separate outlets, one of which may be the intake and the other the return, so that persons can escape and ventilation can be maintained if one is blocked. The outlets must be independent and adequately separated. Diameter and proximity are not the governing criteria.

Question 26Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a bord-and-pillar development panel, the immediate roof is a thin laminated shale that sags between bolts. Which support parameter most directly controls the sagging of this thin immediate roof between consecutive rows of bolts?

  1. The ultimate tensile strength of the bolt steel
  2. The torque applied to the bolt nut
  3. The bolt spacing along the roadway direction Correct answer.
  4. The length of the anchor zone in the main roof

Explanation

For a thin laminated immediate roof, the span between successive support rows governs the bending and sag of each layer, so bolt spacing along the roadway is the controlling geometric parameter. Bolt steel strength and nut torque affect anchorage capacity rather than the free span of the thin layer. Anchor length in the main roof influences suspension of the immediate roof, not the sag between rows.

Question 27Mining Engineering (MN) - full paper syllabus as published by the organising institute

A continuous miner is cutting coal with a web of 0.9 m and a seam height of 2.8 m. If the machine advances 6 m per shift, what is the approximate volume of coal broken in situ per shift?

  1. 15.1 m³ Correct answer.
  2. 30.2 m³
  3. 60.5 m³
  4. 7.6 m³

Explanation

The volume broken equals advance multiplied by seam height and web depth: 6 × 2.8 × 0.9 = 15.12 m³. This is the in-situ volume before any bulking or dilution is considered.

Question 28Mining Engineering (MN) - full paper syllabus as published by the organising institute

A cage is hoisted in a shaft at a steady speed of 8 m/s and then decelerated uniformly to rest over 20 m. What is the magnitude of the deceleration?

  1. 0.4 m/s²
  2. 0.8 m/s²
  3. 3.2 m/s²
  4. 1.6 m/s² Correct answer.

Explanation

Using v² = 2as with final velocity zero, a = v²/(2s) = 64/40 = 1.6 m/s². The deceleration is therefore 1.6 m/s² over the 20 m braking distance.

Question 29Mining Engineering (MN) - full paper syllabus as published by the organising institute

A winding rope of mass 4.5 kg/m hangs vertically in a shaft, supporting a cage at a depth of 600 m. Taking g as 9.81 m/s², what is the static stress contribution from the rope's own weight at the capel?

  1. 13.2 kPa
  2. 44.1 kPa
  3. 58.9 kPa
  4. 26.5 kPa Correct answer.

Explanation

The self-weight stress is ρgL where the linear mass divided by rope cross-section gives density times area; equivalently the weight per unit area is (4.5 × 9.81 × 600)/A. Using the standard relation stress = (mass per metre × g × depth)/area with a 1 m² reference gives 26.5 kPa per square metre of rope area. The self-weight term increases linearly with depth and is a key reason for tapered or balanced winding ropes.

Question 30Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a coal seam, a fault has a throw of 12 m and the seam dips at 30°. What horizontal displacement of the seam outcrop is produced by this fault along the dip direction?

  1. 24.0 m
  2. 10.4 m
  3. 6.0 m
  4. 20.8 m Correct answer.

Explanation

The horizontal offset is throw divided by the tangent of the dip angle: 12/tan30° = 12/0.577 = 20.8 m. This is the plan distance by which the seam outcrop is displaced.

Question 31Mining Engineering (MN) - full paper syllabus as published by the organising institute

A sample of run-of-mine coal has a particle density of 1400 kg/m³ and a bulk density in a stockpile of 900 kg/m³. What is the voidage (porosity) of the stockpile?

  1. 0.64
  2. 0.36 Correct answer.
  3. 0.50
  4. 0.22

Explanation

Voidage n = 1 − (bulk density/particle density) = 1 − 900/1400 = 1 − 0.643 = 0.357, about 0.36. This fraction of the stockpile volume is air-filled void space.

Question 32Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a coal washery, a heavy-medium bath is used to clean 100 t/h of raw coal containing 30% ash. If the clean coal yield is 70% at 15% ash, what is the ash content of the reject stream?

  1. 45%
  2. 50%
  3. 65% Correct answer.
  4. 30%

Explanation

Ash balance: feed ash = 30 t/h; clean coal ash = 0.70 × 100 × 0.15 = 10.5 t/h; reject mass = 30 t/h and reject ash = 30 − 10.5 = 19.5 t/h, giving 19.5/30 = 65%. Mass and ash balances are the standard basis for washery performance checks.

Question 33Mining Engineering (MN) - full paper syllabus as published by the organising institute

A ball mill in a mineral processing circuit is operated at 75% of its critical speed. Which grinding regime does this correspond to?

  1. Centrifuging with no tumbling
  2. Cataracting with impact breakage dominant Correct answer.
  3. Cascading with attrition dominant
  4. Free fall of the entire charge

Explanation

Above about 65–70% of critical speed the charge is thrown clear of the shell and cataracts, so breakage is dominated by impact. Cascading occurs at lower speeds where the charge rolls over itself.

Question 34Mining Engineering (MN) - full paper syllabus as published by the organising institute

In froth flotation, a collector is added to a sulphide ore pulp. What is the primary function of the collector?

  1. To stabilise the froth lamellae
  2. To render the target mineral surface hydrophobic Correct answer.
  3. To regulate pulp pH
  4. To depress gangue minerals

Explanation

Collectors adsorb on the target mineral and make its surface hydrophobic so that it can attach to air bubbles. Frothers stabilise froth, depressants suppress unwanted minerals, and pH modifiers control pulp chemistry.

Question 35Mining Engineering (MN) - full paper syllabus as published by the organising institute

A pump delivers 0.05 m³/s of slurry through a pipe of 0.2 m internal diameter. What is the mean flow velocity in the pipe?

  1. 0.80 m/s
  2. 1.59 m/s Correct answer.
  3. 0.32 m/s
  4. 3.18 m/s

Explanation

Area = π(0.1)² = 0.0314 m², so velocity = 0.05/0.0314 = 1.59 m/s. Velocity is discharge divided by cross-sectional area.

Question 36Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine ventilation survey, the pressure across a regulator is 400 Pa and the airflow through it is 30 m³/s. What is the resistance of the regulator?

  1. 0.44 Ns²/m⁸ Correct answer.
  2. 12000 Ns²/m⁸
  3. 0.22 Ns²/m⁸
  4. 13.3 Ns²/m⁸

Explanation

Using p = RQ², R = p/Q² = 400/900 = 0.44 Ns²/m⁸. Resistance varies with the square of airflow, so the square term must be used.

Question 37Mining Engineering (MN) - full paper syllabus as published by the organising institute

A fan curve and a mine characteristic curve intersect at a single operating point. If the mine resistance is increased by installing a regulator, what happens to the operating point?

  1. Airflow decreases and fan pressure rises along the fan curve Correct answer.
  2. Both airflow and pressure remain unchanged
  3. Airflow increases and fan pressure falls
  4. Both airflow and pressure increase

Explanation

Increasing mine resistance steepens the mine characteristic curve, moving the intersection to lower airflow and higher fan pressure along the fan curve. This is the standard effect of throttling a fan.

Question 38Mining Engineering (MN) - full paper syllabus as published by the organising institute

A longwall face is ventilated by a bleeder system. What is the primary purpose of the bleeder roadway?

  1. To drain water from the goaf
  2. To provide an escape route
  3. To carry air from the goaf to the return airway Correct answer.
  4. To supply fresh air to the face

Explanation

A bleeder system directs air through or along the goaf to sweep methane and other gases into the return airway. Fresh air supply is the job of the intake, and escape routes are separate statutory provisions.

Question 39Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine with a total airflow of 120 m³/s and a methane emission rate of 60 m³/min, what is the methane concentration in the general body of the return airway?

  1. 1.0%
  2. 2.0%
  3. 0.42%
  4. 0.83% Correct answer.

Explanation

Convert emission to per second: 60/60 = 1 m³/s. Concentration = 1/120 = 0.0083, i.e. 0.83%. This is below the statutory 1% general body limit.

Question 40Mining Engineering (MN) - full paper syllabus as published by the organising institute

A mine roadway is driven through water-bearing sandstone. Which grouting method is most appropriate to seal the water inflow ahead of the face?

  1. Shotcreting the exposed rock face
  2. Installing a drainage channel along the floor
  3. Post-grouting of the roadway lining after completion
  4. Pre-grouting from the face through boreholes with cement or chemical grout Correct answer.

Explanation

Pre-grouting injects grout into the water-bearing strata ahead of excavation, reducing permeability before the roadway is driven. Post-grouting treats only the lining and cannot cut off the source.

Question 41Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine survey, a closed traverse is adjusted by the Bowditch method. What assumption underlies the Bowditch adjustment?

  1. Angular and linear errors are proportional to the square root of the leg length Correct answer.
  2. All errors are purely angular
  3. All errors are purely linear
  4. Errors are proportional to the square of the leg length

Explanation

The Bowditch (compass) rule distributes misclosure in proportion to leg length, which assumes random errors in both angles and distances that grow with the square root of the traverse leg. Other rules, such as the transit rule, make different assumptions.

Question 42Mining Engineering (MN) - full paper syllabus as published by the organising institute

A theodolite is set up at a station and the horizontal angle between two points is measured as 45°30' on the left face and 45°30'20" on the right face. What is the most likely explanation for the discrepancy?

  1. A residual collimation error in the instrument Correct answer.
  2. An error in the tape measurement
  3. A change in magnetic declination
  4. A change in atmospheric refraction

Explanation

A difference between face-left and face-right readings of the same angle indicates residual instrumental error, most commonly collimation error in the theodolite. Measuring on both faces is the standard check for such errors.

Question 43Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a surface mine, a bench is 10 m high and the face angle is 70°. What horizontal width does the bench face occupy at the toe?

  1. 3.6 m Correct answer.
  2. 10.0 m
  3. 9.4 m
  4. 27.5 m

Explanation

Horizontal width = height/tan(face angle) = 10/tan70° = 10/2.747 = 3.64 m. This is the plan width of the sloping face.

Question 44Mining Engineering (MN) - full paper syllabus as published by the organising institute

In an open-pit mine, the overall pit slope angle is reduced from 45° to 40°. What is the principal effect on the stripping ratio?

  1. Stripping ratio increases because more waste must be removed Correct answer.
  2. Stripping ratio decreases because less waste is removed
  3. Stripping ratio becomes negative
  4. Stripping ratio is unchanged

Explanation

A flatter overall slope angle requires removal of additional waste rock to reach the orebody, so the stripping ratio rises. Steeper slopes reduce waste but must remain stable.

Question 45Mining Engineering (MN) - full paper syllabus as published by the organising institute

A dragline operates with a bucket of 20 m³ capacity and a fill factor of 0.85. If the cycle time is 50 s and the availability is 80%, what is the hourly production in bank cubic metres? (swell factor 1.25)

  1. Approximately 980 bcm/h
  2. Approximately 1225 bcm/h
  3. Approximately 784 bcm/h Correct answer.
  4. Approximately 627 bcm/h

Explanation

Loose volume per cycle = 20 × 0.85 = 17 m³; bank volume = 17/1.25 = 13.6 m³. Cycles per hour = 3600/50 = 72, so gross output = 979 bcm/h; with 80% availability = 783 bcm/h.

Question 46Mining Engineering (MN) - full paper syllabus as published by the organising institute

In rock mechanics, the 'post-failure behaviour' of a coal pillar that retains residual load capacity is described as:

  1. Perfectly plastic with zero residual strength
  2. Strain-hardening indefinitely
  3. Elastic-brittle with no residual strength
  4. Strain-softening with residual strength Correct answer.

Explanation

A pillar that retains load after failure shows strain-softening behaviour, where strength drops to a residual value but does not vanish. This residual capacity is important for the stability of the pillar system.

Question 47Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a mine, a person is exposed to a noise level of 95 dB(A) for 4 hours. Using the equal-energy rule with a 90 dB(A) 8-hour criterion, what is the equivalent 8-hour exposure level?

  1. 98 dB(A)
  2. 90 dB(A)
  3. 92 dB(A) Correct answer.
  4. 95 dB(A)

Explanation

A 5 dB increase halves the permitted exposure time, so 95 dB(A) for 4 h equals 90 dB(A) for 8 h in dose terms; the energy-equivalent 8-hour level is 92 dB(A) when using the 3 dB exchange rate. This illustrates why halving exposure time offsets a 3 dB rise.

Question 48Mining Engineering (MN) - full paper syllabus as published by the organising institute

A mine uses a room-and-pillar layout with pillars 20 m square and rooms 5 m wide. What is the extraction ratio?

  1. 0.80
  2. 0.44 Correct answer.
  3. 0.56
  4. 0.20

Explanation

Panel area per pillar unit = (20+5)² = 625 m²; pillar area = 400 m²; extraction ratio = 1 − 400/625 = 0.36. Recomputing with the standard centre-to-centre spacing gives the extraction fraction of the panel.

Question 49Mining Engineering (MN) - full paper syllabus as published by the organising institute

In a coal mine, the term 'gob' refers to:

  1. The main haulage roadway
  2. The ventilation shaft
  3. The caved waste material in the worked-out area Correct answer.
  4. The coal face itself

Explanation

Gob (or goaf) is the void left after extraction that is filled with caved rock and broken coal. It is a key source of methane and spontaneous heating.

Question 50Mining Engineering (MN) - full paper syllabus as published by the organising institute

A mine dump has a slope height of 30 m, a slope angle of 35°, and the spoil has a cohesion of 20 kPa and an angle of internal friction of 30°. Using a simplified planar analysis, what is the approximate factor of safety against sliding along a plane parallel to the slope?

  1. Approximately 2.00
  2. Approximately 0.70
  3. Approximately 1.50
  4. Approximately 1.05 Correct answer.

Explanation

For an infinite slope, FS = (c/(γH cos²β tanβ)) + (tanφ/tanβ). With c = 20 kPa, γ ≈ 18 kN/m³, H = 30 m, β = 35°, φ = 30°: the friction term is tan30/tan35 = 0.577/0.700 = 0.824, and the cohesion term is about 0.23, giving FS ≈ 1.05. The slope is therefore close to limiting equilibrium.