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PE Mining practice questions

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Question 1Mining methods and mine planning

The choice between open-pit and underground mining for a given orebody is most directly influenced by which pair of factors?

  1. The colour and crystal habit of ore minerals
  2. Shaft diameter and underground ventilation costs
  3. The brand of loading equipment and local labour rates
  4. Orebody depth and stripping ratio Correct answer.

Explanation

Open-pit and underground options are compared mainly on economics: an open pit must remove waste, so depth and stripping ratio drive cost. As depth and stripping ratio rise, underground methods become more competitive.

Question 2Mining methods and mine planning

A pit must remove 3.0 million tonnes of waste to recover 1.0 million tonnes of ore. What is the stripping ratio expressed as waste:ore?

  1. 4:1
  2. 3:1 Correct answer.
  3. 1:3
  4. 0.33:1

Explanation

Stripping ratio is waste tonnage divided by ore tonnage: 3.0/1.0 = 3:1. It is normally quoted as waste:ore.

Question 3Mining methods and mine planning

In open-pit bench design, bench height is normally limited by which consideration?

  1. The prevailing diesel fuel price
  2. Safe digging reach of the loading equipment Correct answer.
  3. The number of trucks in the haul fleet
  4. The dip angle of the orebody

Explanation

Bench height is set so the loader can safely reach the top of the muckpile and the face remains stable. Truck fleet size, orebody dip, and fuel price do not directly set bench height.

Question 4Mining methods and mine planning

Sublevel stoping is characterized by which combination?

  1. Caving of ore beneath an undercut level and drawbells
  2. Slicing and backfilling after every cut
  3. Room-and-pillar extraction with a continuous miner
  4. Longhole drilling from sublevels into an open stope, with draw from below Correct answer.

Explanation

Sublevel stoping uses longhole drilling from sublevels, blasts into an open stope, and draws broken ore from a lower extraction level. It relies on stable walls and controlled draw.

Question 5Mining methods and mine planning

Block caving is best suited to which type of deposit?

  1. Narrow, high-grade vein requiring highly selective mining
  2. Small remnant pillar recovery in an old room-and-pillar mine
  3. Flat-lying coal seam at shallow depth
  4. Massive, low-grade orebody with a caveable rock mass Correct answer.

Explanation

Block caving requires a large, low-grade orebody that can be undercut and allowed to cave, with drawbells collecting broken ore. It is a bulk, low-cost method with significant subsidence.

Question 6Mining methods and mine planning

In room-and-pillar mining, pillars are left in place primarily to:

  1. Store broken ore until it can be hoisted
  2. Serve as ore passes to the haulage level
  3. Support the overlying roof Correct answer.
  4. Act as ventilation shafts

Explanation

Pillars carry the overburden load and control roof convergence. They are not ore storage, ventilation shafts, or ore passes.

Question 7Mining methods and mine planning

Longwall mining extracts coal by:

  1. Using a continuous miner in a room-and-pillar layout
  2. Advancing a long face with a shearer and caving the roof Correct answer.
  3. Driving rooms and leaving pillars to support the roof
  4. Blasting ore into an open stope and drawing it from below

Explanation

Longwall mining advances a long coal face with a shearer, while powered supports hold the roof at the face and the roof is allowed to cave behind. It is a high-extraction coal method.

Question 8Mining methods and mine planning

Cut-and-fill stoping is most appropriate when:

  1. The ore is very low grade and extensive
  2. The orebody is massive and can be caved economically
  3. The deposit is a flat-lying coal seam
  4. Wall rock is too weak to stand in an open stope Correct answer.

Explanation

Cut-and-fill is selected for steep orebodies with incompetent walls because each slice is backfilled to support the walls and allow selective mining. It is relatively expensive and suited to higher-grade ore.

Question 9Mining methods and mine planning

A key operational limitation of shrinkage stoping is that:

  1. It requires no drilling or blasting at all
  2. It can only be used in flat-lying coal seams
  3. Paste backfill is required after every mining slice
  4. Broken ore must stay in the stope for wall support Correct answer.

Explanation

Shrinkage stoping leaves broken ore in the stope to support the walls; this ties up ore and can cause dilution and safety issues, especially in weak rock. The stope is drawn down only after most of the slice is completed.

Question 10Mining methods and mine planning

Vertical crater retreat (VCR) mining relies on:

  1. Upward crater blasting from longholes Correct answer.
  2. Room-and-pillar extraction with a continuous miner
  3. Caving of ore beneath an undercut level
  4. Bucket-wheel excavation of a shallow seam

Explanation

VCR uses longhole charges fired to crater upward; slices retreat upward and broken ore is drawn from the bottom. It is a bulk stoping method that depends on controlled longhole blasting.

Question 11Mining methods and mine planning

A stope produces 1,000 t of ore at 2.0% Cu and mixes with 100 t of waste at 0.0% Cu. What is the diluted grade?

  1. 1.67% Cu
  2. 1.82% Cu Correct answer.
  3. 2.00% Cu
  4. 2.20% Cu

Explanation

Copper content is 1,000 × 0.02 = 20 t. Total diluted mass is 1,100 t, so grade is 20/1,100 = 1.82% Cu.

Question 12Mining methods and mine planning

The cut-off grade is best defined as:

  1. The highest grade intersected in the deposit
  2. The average grade of all drill core
  3. The grade of the final concentrate
  4. The grade where ore and waste break even Correct answer.

Explanation

Cut-off grade is the break-even grade at which the value of contained metal just covers mining, processing, and other costs. Material below it is treated as waste.

Question 13Mining methods and mine planning

In mineral resource classification, the categories in order of increasing geological confidence are:

  1. Indicated, Inferred, Measured
  2. Inferred, Indicated, Measured Correct answer.
  3. Proved, Probable, Possible
  4. Measured, Indicated, Inferred

Explanation

Resources are classified by increasing confidence as Inferred, then Indicated, then Measured. Proved and Probable are reserve categories, not resource categories.

Question 14Mining methods and mine planning

Increasing the overall pit slope angle generally:

  1. Increases stripping and reduces slope-failure risk
  2. Reduces waste stripping but raises slope-failure risk Correct answer.
  3. Requires wider haul roads but no geotechnical work
  4. Has no effect on project economics

Explanation

Steeper slopes reduce waste stripping but decrease stability. The optimum overall slope angle is set by geotechnical analysis, not by haul-road width alone.

Question 15Mining methods and mine planning

For large surface haul trucks, the maximum sustained haul-road grade is typically limited to about:

  1. 1% to 2%
  2. 25% to 30%
  3. 8% to 10% Correct answer.
  4. 15% to 20%

Explanation

Haul-road grades are usually kept around 8–10% for large trucks. Steeper grades reduce speed and safety, while very flat grades increase haul distance.

Question 16Mining methods and mine planning

In an open-pit mine, switchbacks in ramp design are used primarily to:

  1. Improve pit drainage
  2. Reduce tyre wear on haul roads
  3. Gain elevation in a confined pit at safe grades Correct answer.
  4. Increase truck speed on straight sections

Explanation

Switchbacks let a ramp gain elevation in a confined pit while keeping each segment at a truckable gradient. They are a geometric design tool, not a speed or drainage measure.

Question 17Mining methods and mine planning

The Lerchs-Grossmann algorithm is used to:

  1. Determine the ultimate pit limit Correct answer.
  2. Design the blast pattern
  3. Classify mineral resources
  4. Calculate ventilation airflow

Explanation

Lerchs-Grossmann is a pit-optimization algorithm that uses a block model and slope constraints to find the maximum-value ultimate pit. It does not design blasts or classify resources.

Question 18Mining methods and mine planning

Why are open pits often designed and mined in phases (pushbacks) rather than to the final limit in one operation?

  1. To increase the final stripping ratio
  2. To avoid using haul trucks
  3. To eliminate the need for geotechnical assessment
  4. To defer waste stripping and reach ore sooner Correct answer.

Explanation

Phasing defers waste stripping, improves cash flow, and allows earlier access to higher-grade ore. It does not remove geotechnical work or haul trucks.

Question 19Mining methods and mine planning

The primary purpose of main mine ventilation is to:

  1. Supply air and remove contaminants Correct answer.
  2. Support the hangingwall
  3. Reduce blast-hole spacing
  4. Increase ore grade by selective leaching

Explanation

Ventilation supplies oxygen, dilutes and removes dust, diesel fumes, and blasting gases, and controls temperature. It does not change ore grade or support rock.

Question 20Mining methods and mine planning

For a deep, high-tonnage underground mine, a vertical shaft is often preferred over a decline because:

  1. Shafts improve ventilation only in coal mines
  2. Shafts hoist large tonnages from depth efficiently Correct answer.
  3. Shafts require no hoisting equipment
  4. Declines are always cheaper at any depth

Explanation

Shafts use hoists and are efficient for high tonnage from depth. Declines rely on truck haulage and become expensive as depth and haul distance increase.

Question 21Mining methods and mine planning

Paste backfill is typically prepared from:

  1. Crushed waste rock only
  2. Pure cement slurry
  3. Seawater and gravel
  4. Dewatered tailings with binder Correct answer.

Explanation

Paste fill is made from dewatered tailings plus a small amount of cementitious binder. It is not pure cement or coarse rock alone.

Question 22Mining methods and mine planning

An ore pass in an underground mine is used to:

  1. Store explosives underground
  2. Carry ventilation air
  3. Pump water to the surface
  4. Transfer broken ore by gravity to a lower level Correct answer.

Explanation

An ore pass is a vertical or inclined opening that moves broken ore by gravity from a higher level to a lower haulage or loading level. It is not a water line, airway, or explosive magazine.

Question 23Mining methods and mine planning

If 200 kg of explosive is used to break 1,000 t of rock, the powder factor is:

  1. 5 kg/t
  2. 2 kg/t
  3. 0.02 kg/t
  4. 0.2 kg/t Correct answer.

Explanation

Powder factor is explosive mass divided by rock mass: 200 kg / 1,000 t = 0.2 kg/t. It is a key blasting design and cost indicator.

Question 24Mining methods and mine planning

In production blasting, accurate delay timing between holes in a row is primarily used to:

  1. Reduce explosive consumption to zero
  2. Increase the number of misfires and reduce blast efficiency
  3. Improve breakage by stress-wave and gas interaction Correct answer.
  4. Eliminate the need for stemming

Explanation

Delay timing separates charges so stress waves and gas pressure interact, improving fragmentation and muckpile shape while reducing vibration. It does not remove the need for stemming.

Question 25Mining methods and mine planning

A deposit contains 12 Mt of recoverable ore and the mine plans to produce 1.5 Mt/y. What is the approximate mine life?

  1. 1.5 years
  2. 8 years Correct answer.
  3. 18 years
  4. 80 years

Explanation

Mine life is approximately recoverable ore divided by annual production: 12/1.5 = 8 years. This simple estimate ignores ramp-up, dilution, and scheduling changes.

Question 26Mining methods and mine planning

Block caving extracts an orebody mainly by:

  1. Drilling and blasting each production bench in sequence from the top down
  2. Dissolving the ore in place with a circulating leach solution
  3. Undercutting the orebody so it caves under gravity and is drawn from below Correct answer.
  4. Slicing the ore in horizontal lifts blasted against a backfilled face

Explanation

Block caving is a mass-mining method that relies on natural caving rather than on blasting the ore itself. An undercut is developed beneath the block, the rock mass fractures and subsides, and broken ore is drawn from drawpoints underneath while new rock caves into the void. The method therefore requires a rock mass that will cave readily and a substantial capital development in the undercut and drawbell levels.

Question 27Mining methods and mine planning

In-situ leaching is most likely to be technically suited to:

  1. A permeable sandstone-hosted uranium deposit in a confined aquifer Correct answer.
  2. A narrow, steeply dipping gold-quartz vein in hard, competent rock
  3. A flat-lying coal seam 200 m deep under a competent sandstone roof
  4. A massive sulphide deposit containing abundant swelling clays

Explanation

Solution mining requires a host rock permeable enough for the lixiviant to flow between injection and recovery wells, a mineral that dissolves readily, and a confined aquifer that keeps the solution from escaping. Sandstone-hosted uranium and some oxide copper deposits satisfy these conditions. Low-permeability or clay-rich hosts prevent adequate flow and make containment difficult.

Question 28Mining methods and mine planning

Which plan covers the full reserve life of a mining project and provides the basis for valuation and reserve declaration?

  1. The weekly shovel-and-truck schedule
  2. The monthly grade control plan
  3. The three-month rolling forecast
  4. The life-of-mine plan Correct answer.

Explanation

Mine planning is hierarchical: short-interval schedules control day-to-day operations, while the life-of-mine plan covers the entire reserve and sets annual production, capital timing and cash flow. Because it defines what is economically mineable, the life-of-mine plan underpins project valuation and the ore reserve statement. Shorter-horizon plans must remain consistent with it.

Question 29Mining methods and mine planning

A pit must strip 4.5 Mt of waste to produce 1.5 Mt of ore. What is the stripping ratio, expressed as tonnes of waste per tonne of ore?

  1. 4.5 : 1
  2. 0.33 : 1
  3. 6 : 1
  4. 3 : 1 Correct answer.

Explanation

Stripping ratio is waste tonnage divided by ore tonnage, so 4.5 divided by 1.5 gives 3, written 3 : 1. It is a key economic driver because all waste tonnes must be handled without generating revenue. The ratio is compared against a break-even value to test whether the material is worth mining.

Question 30Mining methods and mine planning

Sublevel stoping is generally best suited to an orebody that is:

  1. A narrow vein in altered ground needing close grade control
  2. Flat-lying and thick in weak rock needing full back support
  3. Steeply dipping, competent ore and walls, with regular boundaries Correct answer.
  4. Very low grade with a large footprint and readily caving rock

Explanation

Sublevel stoping leaves large open stopes that must stand until they are mucked out, so the ore and both walls must be competent and the dip must be steep enough for broken rock to flow by gravity. Regular orebody boundaries allow efficient ring drilling and minimise dilution. Weak or irregular orebodies are better handled by supported or selective methods.

Question 31Mining methods and mine planning

Pillars in a room-and-pillar panel occupy 35% of the panel area. What is the extraction ratio?

  1. 35%
  2. 135%
  3. 50%
  4. 65% Correct answer.

Explanation

Extraction ratio is the fraction of the orebody actually mined, calculated here as 1 minus the pillar fraction, giving 0.65 or 65%. It is a simple area-based proxy that ignores losses and dilution, but it captures the central trade-off between recovery and ground stability. Raising the extraction ratio by shrinking pillars reduces support and increases the risk of pillar failure.

Question 32Mining methods and mine planning

Why do many operations stockpile rock that lies below the current cut-off grade instead of trucking it to the waste dump?

  1. Stockpiles keep the crusher supplied with a constant grade of feed
  2. The rock can be used as ballast in mill foundations
  3. The material may become economic ore if metal prices rise or costs fall Correct answer.
  4. Regulations prohibit returning mineralised rock to a waste dump

Explanation

Cut-off grade is not fixed: it depends on metal price, processing cost, recovery and capacity, so marginal material can move in or out of the reserve as these change. Stockpiling sub-cut-off rock preserves the option to process it later at little extra cost beyond rehandling. This is a deliberate planning decision rather than a regulatory or blending requirement.

Question 33Mining methods and mine planning

In an open stoping operation using delayed backfill, why is cemented backfill placed in primary stopes?

  1. So that adjacent secondary stopes can be mined against a stable fill wall Correct answer.
  2. To raise the head grade by blending cement with the broken ore
  3. To cut the amount of ventilation air needed on the stoping horizon
  4. To seal the stope walls against groundwater inflow from the hangingwall

Explanation

Primary and secondary stoping allows wide orebodies to be extracted in alternating panels, with primaries mined and filled first. Cement gives the fill enough cohesion to stand unsupported, so the neighbouring secondary stope can be blasted against it with limited dilution and ore loss. Uncemented fill is normally adequate in the secondary stopes, which are bounded by solid rock on both sides.

Question 34Mining methods and mine planning

An operation raises its cut-off grade while metal prices and costs are unchanged. What is the typical expected effect?

  1. The stripping ratio of an operating open pit necessarily rises
  2. Ore reserves increase and the mine life is extended
  3. Ore tonnage in reserves falls while the remaining ore has a higher average grade Correct answer.
  4. Both ore tonnage and contained metal in reserves increase

Explanation

A cut-off grade is the grade at which a tonne of material just pays for itself, so raising it reclassifies marginal low-grade material as waste. Reserve tonnage therefore falls while average grade of what remains rises, which can improve cash margin per tonne but usually shortens mine life and reduces total contained metal. The change is a scheduling and value decision, not an automatic improvement in the deposit.

Question 35Geotechnical engineering and ground control

In diamond core logging, rock quality designation (RQD) is calculated as:

  1. sum of fractured intervals divided by the length of the run
  2. sum of intact core pieces over 100 mm divided by the length of the run Correct answer.
  3. sum of all recovered core divided by the length of the core barrel
  4. sum of core pieces over 10 mm divided by the length of the run

Explanation

RQD counts only natural intact pieces longer than 100 mm and expresses them as a percentage of the total length of the core run. It is a double-directive index of core recovery and fragmentation and is sensitive to the chosen threshold length. It is used as a stand-alone indicator of rock mass quality and as an input to both the RMR and Q systems.

Question 36Geotechnical engineering and ground control

Under drained conditions, the shear strength of a rock joint is best represented as:

  1. cohesion plus normal stress times the tangent of the friction angle Correct answer.
  2. a purely cohesive value independent of normal stress
  3. a tensile cut-off that applies at zero confining pressure
  4. a residual value that is always equal to the peak value

Explanation

The Mohr-Coulomb envelope combines an intercept (cohesion, near zero for most fresh joints) with a frictional term that grows with effective normal stress. The friction term is the effective normal stress multiplied by the tangent of the friction angle. Peak and residual envelopes differ, with residual reflecting sliding after asperities are sheared off.

Question 37Geotechnical engineering and ground control

The factor of safety of a slope is defined as the ratio of:

  1. slope height to slope horizontal width
  2. driving shear stress to available shear strength
  3. pore pressure to total normal stress on the failure plane
  4. available shear strength to driving shear stress Correct answer.

Explanation

The factor of safety compares the shear strength that the soil or rock can mobilise along a candidate failure surface with the shear stress required for equilibrium. A value above one indicates a margin against failure. Values near or below one indicate marginal or unstable conditions.

Question 38Geotechnical engineering and ground control

Terzaghi's principle of effective stress states that:

  1. effective stress equals total stress minus pore pressure Correct answer.
  2. pore pressure equals total stress minus shear stress
  3. effective stress equals total stress plus pore pressure
  4. total stress equals effective stress plus shear stress

Explanation

Effective stress is the intergranular stress carried by the soil skeleton and controls strength and compressibility. It equals total stress minus the pore water pressure acting in the voids. Only changes in effective stress produce changes in volume or shear resistance in saturated soil.

Question 39Geotechnical engineering and ground control

A fully grouted resin rock bolt transfers load to the surrounding rock mainly through:

  1. adhesion and shear along the full grouted length Correct answer.
  2. compression of the face plate against the rock surface
  3. a mechanical expansion shell gripping near the toe
  4. bending resistance of the bolt shank alone

Explanation

A fully encapsulated bolt bonds to the borehole wall over its entire length, so load is shed gradually into the rock mass by adhesive and shear stresses in the grout column. This gives a stiff, distributed load transfer rather than a single point of anchorage. The plate contributes only near the collar.

Question 40Geotechnical engineering and ground control

For a given pillar height and rock type, pillar strength generally:

  1. is independent of pillar dimensions
  2. decreases as pillar width increases
  3. increases as the width-to-height ratio increases Correct answer.
  4. increases as pillar width decreases

Explanation

Empirical and analytical pillar strength formulas scale strength with the width-to-height ratio, because wider pillars have a larger confined core relative to the height. Increasing width at constant height therefore raises strength. Decreasing width reduces the confined core and lowers strength.

Question 41Geotechnical engineering and ground control

In longwall subsidence, the angle of draw is the angle between the vertical and the line from:

  1. the extracted seam to the base of the weathered zone
  2. the goaf to the rear of the powered supports
  3. the caved zone to the top of the fractured zone
  4. the panel edge to the surface limit of measurable movement Correct answer.

Explanation

The angle of draw defines how far surface movement extends beyond the extracted panel edge. It is measured from the vertical at the panel edge out to the point where surface displacement becomes negligible. Its value depends on the overburden character and is used to define surface subsidence boundaries and protection zones.

Question 42Geotechnical engineering and ground control

A borehole extensometer installed in a rock mass is used primarily to:

  1. measure the rate of water inflow
  2. measure pore water pressure at depth
  3. determine the in-situ stress tensor
  4. measure displacement along the borehole axis Correct answer.

Explanation

A multipoint extensometer anchors at several depths and measures the relative movement between anchors and the collar, giving axial displacement and the location of the moving zone. This allows identification of the active bedding or discontinuity where separation occurs. Pore pressure and stress require different instruments.

Question 43Geotechnical engineering and ground control

In the RMR classification, the discontinuity orientation term:

  1. applies a penalty adjustment for unfavourable discontinuity orientation Correct answer.
  2. is a constant zero for every rock type
  3. is added only when the rock mass is completely dry
  4. is determined solely by the uniaxial compressive strength

Explanation

RMR assigns a rating adjustment, usually negative, based on how favourably the dominant discontinuity set is oriented relative to the excavation being assessed. The same rock mass can therefore score differently for a tunnel, a foundation or a slope. The adjustment is applied after the five base ratings are summed.

Question 44Geotechnical engineering and ground control

In the Q system, the ratio Jr/Ja describes:

  1. the block size of the rock mass
  2. the stress condition around the tunnel
  3. the roughness and alteration of the joints Correct answer.
  4. the groundwater pressure acting on the tunnel

Explanation

Q combines three quotients, and the second one, Jr/Ja, compares joint roughness number with joint alteration number. It therefore captures how frictional and clean, versus how smooth and clay-coated, the discontinuities are. The other quotients cover block size and active stress plus water.

Question 45Geotechnical engineering and ground control

The Geological Strength Index (GSI) for a rock mass is estimated primarily from:

  1. blockiness and the surface condition of discontinuities Correct answer.
  2. joint spacing and tunnel span
  3. uniaxial compressive strength and point load index
  4. RQD and groundwater inflow

Explanation

GSI is read from a chart whose axes are the structure of the rock mass (blockiness or disturbance) and the surface condition of the discontinuities. It is a qualitative but systematic estimate of the reduction in strength from intact rock to rock mass. It does not use water or stress directly.

Question 46Geotechnical engineering and ground control

In the Hoek-Brown failure criterion, the disturbance factor D accounts for:

  1. the depth of weathering below the surface
  2. the degree of saturation of the rock mass
  3. blast damage and stress relaxation adjacent to the excavation Correct answer.
  4. the size of the laboratory specimen tested

Explanation

D ranges from zero for undisturbed in-situ rock to one for severely disturbed rock and modifies the rock mass parameters. It represents the loss of interlocking and confinement caused by blasting and by stress relief near an opening. Its selection should reflect the excavation method and the quality of blasting control.

Question 47Geotechnical engineering and ground control

For plane sliding on a single discontinuity in a rock slope, the discontinuity must:

  1. dip out of the slope face at an angle between the friction angle and the slope face angle Correct answer.
  2. dip vertically regardless of the slope face orientation
  3. lie parallel to the slope contours only
  4. dip into the slope face at any angle

Explanation

Plane failure needs the discontinuity to daylight in the face, so its dip must be less steep than the face and steeper than the friction angle for sliding to be kinematically and frictionally possible. Release surfaces at the ends of the block are also required. A discontinuity dipping into the slope cannot daylight.

Question 48Geotechnical engineering and ground control

A strainburst is most likely to develop where:

  1. a stiff, strong rock mass is subjected to highly concentrated stress Correct answer.
  2. groundwater pressures are unusually high
  3. a soft rock mass yields gradually under low stress
  4. the opening is fully supported by steel sets and mesh

Explanation

Strainbursts occur when a strong, brittle rock mass stores large amounts of elastic strain energy and then fails violently as the stress concentration at the excavation boundary exceeds the rock strength. They are associated with high stress, stiff rock and rapid energy release. Yielding ground and high water produce different failure modes.

Question 49Geotechnical engineering and ground control

Flow liquefaction of a loose, saturated tailings deposit is triggered primarily by:

  1. chemical reaction of the tailings with atmospheric oxygen
  2. gradual consolidation under the deposited beach load
  3. undrained loading that causes collapse of the loose structure Correct answer.
  4. freezing and thawing of the beach surface

Explanation

Loose, saturated sands and tailings can collapse structurally when sheared without drainage, transferring stress to the pore water and generating a rapid loss of strength. The result is a sudden flow failure that can travel long distances. Contractive behaviour and saturations above the water table are the key preconditions.

Question 50Geotechnical engineering and ground control

The standard Proctor compaction test is performed to determine:

  1. the permeability of compacted fill at field density
  2. the in-situ density of an existing deposit
  3. the optimum moisture content and maximum dry density Correct answer.
  4. the shear strength of compacted fill at saturation

Explanation

Compacting the same soil at a series of moisture contents produces a compaction curve, whose peak gives the maximum dry density and the corresponding optimum moisture content. These values define the laboratory reference for field compaction control. They are obtained under a standardised compactive effort.