250 MCQ Types of Supports & Stowing in Mining
Underground mining requires strong and reliable support systems to prevent roof collapse, control sidewall movement and maintain overall stability of the excavation. As the excavation progresses, the surrounding rock becomes vulnerable due to stress redistribution. This is why mine supports and stowing operations form the backbone of underground safety.
What Are Mine Supports?
Mine supports are structural elements installed in underground workings to hold the roof, stabilize the ribs, prevent the fall of loose rock and maintain the shape of the excavation. Based on their purpose, supports are categorized as:
1. Temporary Supports
Used during development work, drivages, and areas where long-term stability is not required.
2. Permanent Supports
Installed in haulage roadways, longwall panels, junctions, and high-stress zones where continuous safety is essential.
Types of Mine Supports
1. Timber Supports
Timber has been traditionally used for centuries because of its availability and flexibility. Props, chocks, bars, and cog supports are common. Timber absorbs shock loads and gives warning before failure, but its strength is limited and it is prone to moisture and decay.
2. Steel Supports
Steel replaced timber in most modern mines. Steel props, arcs (ribs), chocks and friction props provide greater strength and durability. They are fire-resistant and withstand heavy loads, making them suitable for deep, high-stress mines.
3. Powered Roof Supports (PRS)
Longwall mines use hydraulic shields known as Powered Roof Supports. They offer high bearing capacity, fast operation, and excellent safety. PRS systems automatically support the roof immediately after the shearer passes.
4. Rock Bolts & Cable Bolts
These are the most widely used supports today. Roof bolts form a “self-supporting arch” by binding fractured rock layers. Cable bolts provide deeper reinforcement in large stopes.
5. Shotcrete & Concrete
Shotcrete (sprayed concrete) coats the walls and roof to prevent falling of loose rock. It is often used with rock bolts for superior ground control.
6. Packwalls & Goaf Supports
Material-filled packs support the roof in longwall goaf areas and prevent uncontrolled caving.
What Is Stowing?
Stowing is the process of filling the goaf or mined-out void with material to control subsidence, support the roof, and increase extraction. It is essential in both coal and metal mines, especially where the overburden is weak or surface structures exist.
Types of Stowing
- Hydraulic Stowing: Sand/flyash mixed with water and pumped into voids.
- Pneumatic Stowing: Dry material blown into stopes using compressed air.
- Sand Stowing: Traditional and widely used in coal mines.
- Flyash Stowing: Economical and eco-friendly.
- Paste Fill: Cemented tailings used in deep metal mines.
- Dry Stowing: Manual or mechanical filling in small veins.
Why Supports + Stowing Are Essential
Together, they prevent roof falls, control fire risk, reduce air leakage, allow higher extraction ratios, control subsidence, and maintain roadway stability. Modern mines use a combination of support systems and engineered stowing to achieve maximum safety and productivity.
250 MCQ On Types of Supports & Stowing in Mining
1. The primary purpose of a mine support is to:
Answer: d)
Supports prevent roof fall, stabilize walls, and maintain excavation safety.
2. Which support is traditional, flexible, but prone to decay?
Answer: c)
Timber is widely used but prone to moisture and biological degradation.
3. Which support provides immediate control in longwall mining?
Answer: c)
PRS shields give continuous, strong roof support during longwall operations.
4. Rock bolts mainly function to:
Answer: b)
Bolts create a self-supporting rock arch by anchoring layers together.
5. Which material is commonly used in hydraulic stowing?
Answer: c)
Hydraulic stowing mixes sand with water to form slurry that flows into voids.
6. Pneumatic stowing uses:
Answer: b)
Compressed air propels dry fill material into stopes for dense packing.
7. Which support is most suitable for temporary development headings?
Answer: b)
Timber props are ideal for short-term, flexible use during drivage.
8. Cable bolts are used when:
Answer: b)
Cable bolts provide deep reinforcement for wide spans.
9. Shotcrete is used to:
Answer: b)
Shotcrete seals loose rock and prevents spalling.
10. Which stowing method creates the highest strength fill?
Answer: c)
Paste fill uses cement binder, providing very high compressive strength.
11. Packwalls are generally built from:
Answer: b)
Packwalls fill goaf edges and prevent caving into roadways.
12. Main advantage of hydraulic stowing:
Answer: b)
Slurry flows into complex void shapes better than dry fill.
13. Yielding props are designed to:
Answer: b)
They safely deform under load, preventing brittle collapse.
14. Steel arches are commonly used in:
Answer: a)
Steel ribs support tunnel roofs in soft rock conditions.
15. Flyash stowing is beneficial because:
Answer: b)
Flyash is cheap and reduces environmental waste disposal issues.
16. Major drawback of pneumatic stowing:
Answer: b)
Compressed air creates dust; compressors increase cost.
17. Rock bolts + shotcrete form a:
Answer: b)
Combining bolts and shotcrete provides superior stability.
18. Waste rock backfill is common in:
Answer: b)
Metal mines generate huge waste rock which is reused as backfill.
19. Which method uses cement + tailings as support?
Answer: b)
Paste fill creates artificial pillars with high strength.
20. Which support deforms safely under load?
Answer: b)
Friction props absorb energy through controlled deformation.
21. Best property combination for stowing material:
Answer: b)
Stowing needs flow + strength + availability.
22. Paste fill is preferred because it:
Answer: b)
Cemented paste fill becomes strong enough to act like artificial pillars.
23. Temporary supports are NOT used for:
Answer: c)
Permanent roadways need steel, concrete or engineered supports.
24. Which stowing method consumes maximum water?
Answer: b)
Hydraulic stowing relies on large volumes of slurry.
25. Rock bolts + shotcrete combination gives:
Answer: b)
Composite systems give better structural stability.
26. Packwall is used to:
Answer: b)
Packwalls prevent roof from collapsing into roadways.
27. Key monitoring after stowing:
Answer: b)
Settlement monitoring ensures fill behaves as designed.
28. Which combination controls rock burst risk?
Answer: b)
Cable bolts stabilize deeper rock; yielding supports absorb energy.
29. Best stowing where water contamination must be minimized:
Answer: b)
Paste fill contains minimal free water and is environmentally controlled.
30. Light timber is NOT suitable for:
Answer: b)
Deep mines require strong engineered steel or bolting systems.
31. Common issue with hydraulic pipelines:
Answer: b)
Slurry pipelines face abrasion and choke if not maintained.
32. Most adjustable support type:
Answer: b)
Hydraulic props can be set and adjusted quickly.
33. Best circular economy practice:
Answer: b)
Reusing waste reduces surface dumps and supports ground.
34. Environmental concern with hydraulic fill:
Answer: b)
Hydraulic fill requires water and produces return water needing treatment.
35. Precast concrete units provide:
Answer: b)
Precast units are engineered for consistent strength.
36. Paste fill is superior because:
Answer: b)
Paste fill supports stopes with engineered high strength.
37. Bolt spacing depends on:
Answer: b)
Bolt spacing is designed from rock classification systems.
38. Backfilling reduces:
Answer: b)
Backfill reduces need for large waste dumps.
39. Goaf refers to:
Answer: b)
Goaf is the collapsed area left after extraction.
40. Importance of compaction in stowing:
Answer: b)
Compaction improves fill contact and reduces settlement.
41. Higher extraction ratio achieved using:
Answer: b)
CPF allows safe recovery of more ore by supporting stopes.
42. DGMS focuses on which stowing factor?
Answer: b)
DGMS ensures safe stowing, water management & environmental protection.
43. Strongest fill type:
Answer: b)
CPF attains very high compressive strength after curing.
44. Seismic areas require:
Answer: b)
Supports must absorb dynamic loads in seismic zones.
45. Mesh is used to:
Answer: a)
Mesh anchors surface rock and prevents small fallouts.
46. Stowing required when:
Answer: b)
Stowing prevents dangerous surface subsidence.
47. Rock bolts + cable bolts provide:
Answer: a)
Combining both gives layered support coverage.
48. Paste fill challenge:
Answer: b)
Proper binder & water ratio is essential in CPF.
49. Chock shields are used to:
Answer: b)
PRS shields protect workers and machinery on longwall faces.
50. Stowing sequence planning ensures:
Answer: b)
Sequence planning avoids piping, flooding and uneven compaction.
51. Which element resists shear and binds the rock mass?
Answer: b)
Bolts provide shear resistance by tying discontinuities and creating a stronger rock mass.
52. What limits the use of timber supports?
Answer: b)
Timber degrades, is bulky and has limited load capacity compared with modern steel or bolting systems.
53. Which stowing method is preferred where water management is constrained?
Answer: b)
Paste fill has minimal free water and is easier to contain and manage environmentally.
54. Principal aim of support design is to:
Answer: b)
Design focuses on safe, stable openings under expected loads while allowing operations to continue.
55. Which stowing approach reduces spontaneous combustion risk in coal goaf?
Answer: b)
Filling reduces oxygen availability, limiting oxidation and spontaneous heating of coal residues.
56. A ‘stope’ is:
Answer: b)
Stopes are excavated spaces produced by stoping methods to extract ore underground.
57. Advantage of pre-cast concrete segments is:
Answer: b)
Pre-cast elements are engineered for load, enable quick erection and offer predictable performance.
58. In narrow vein mining, common fill method is:
Answer: b)
Dry backfill and packs are practical where paste/pipelines are impractical for narrow workings.
59. Settling tank function in hydraulic stowing is to:
Answer: b)
Settling tanks deposit solids so the clear water can be reused, reducing fresh water demand.
60. Which is NOT desired in stowing sand?
Answer: c)
Organic or clay-rich sand impairs flow and strength; clean, graded sand is preferred.
61. Immediate check after installing permanent supports should include:
Answer: b)
Ensuring supports are correctly seated and can bear the design loads is essential for safety.
62. Best practice for waste rock backfill is to:
Answer: b)
Processing and controlled placement enhance fill performance and limit voids.
63. Quick temporary support in limited resources is:
Answer: b)
Timber cribbing is often used during emergencies or where resources are constrained.
64. Instruments to detect piping or void migration include:
Answer: b)
Instrumentation shows pressure changes and movements early, allowing intervention.
65. Strength testing for cured paste fill is done by:
Answer: b)
Compressive tests confirm the fill meets design strength to support loads.
66. Indicator of poor support performance includes:
Answer: b)
Unplanned large movements or failures indicate inadequate support and need immediate action.
67. Emergency roof support usually involves:
Answer: b)
Remedial supports stabilize the area quickly until a permanent fix is applied.
68. Choice between pneumatic and hydraulic stowing depends on:
Answer: b)
Hydraulic needs water and pipelines; pneumatic suits dry, steep stopes but requires compressors.
69. When a misfire is found in a stowed area you should:
Answer: b)
Misfires require controlled procedures for safety and to prevent accidental initiation.
70. Grout curtains in stowing schemes are used to:
Answer: b)
Grout curtains form barriers to control seepage and isolate contaminated zones.
71. Why is pilot testing recommended before full-scale stowing?
Answer: b)
Trials reveal practical issues and confirm design assumptions before full implementation.
72. To reduce worker exposure during stowing, use:
Answer: b)
Mechanization and remote systems reduce exposure to dust, pinch points and collapse risk.
73. Concern when using flyash is:
Answer: b)
Flyash requires dust control and monitoring for leachate and chemical interactions.
74. Key control for paste fill plants is:
Answer: b)
Consistent mix ensures pumpability and final strength of paste fills.
75. Typical support for temporary haulage heading is:
Answer: b)
Temporary props protect during development until permanent supports are fitted.
76. Pipeline integrity checks include:
Answer: b)
Regular testing prevents leaks, blockages and environmental incidents.
77. To prevent local slab failure use:
Answer: b)
Anchoring slabs and holding them with mesh and shotcrete prevents small falls of ground.
78. Daily stowing records should include:
Answer: b)
Detailed logs ensure traceability, performance monitoring and regulatory compliance.
79. To stabilise a deteriorating roadway retrofit with:
Answer: b)
Applying bolts, shotcrete or steel restores stability and extends life of the roadway.
80. Poor compaction in fill leads to:
Answer: b)
Voids cause delayed settlement and possible roof fall or surface subsidence.
81. For environmental compliance select stowing materials that are:
Answer: b)
Materials must not leach contaminants; testing and containment are often required.
82. Mechanised bolting rigs provide:
Answer: b)
Mechanisation reduces exposure and improves installation quality.
83. To improve stowing safety use:
Answer: b)
Access control and monitoring reduce accident risk during filling operations.
84. Rock bolting pattern depends mainly on:
Answer: b)
Geological mapping determines spacing and layout to control expected failure modes.
85. Essential maintenance for long-term supports includes:
Answer: b)
Inspections and monitoring detect deterioration early to allow remedial action.
86. To prevent gas migration from goaf, choose:
Answer: b)
Dense or cemented fills minimize voids and pathways for gas movement.
87. Modular steel arches provide:
Answer: b)
Modular arches speed up construction and can be moved as headings progress.
88. Sign of good fill performance is:
Answer: b)
Controlled consolidation indicates the fill is behaving as designed and providing support.
89. Pipeline wear is mainly influenced by:
Answer: b)
High velocities and coarse particles erode pipe walls; material selection and velocity control help.
90. Junctions of haulages typically require:
Answer: b)
Higher traffic and stress at junctions need durable, permanent supports to ensure safety and access.
91. Drainage management in hydraulic stowing aims to:
Answer: b)
Recovering water reduces fresh water demand and controls environmental discharge risks.
92. Temporary control at stoping faces commonly uses:
Answer: b)
Bolts and mesh stabilise the face during excavation until permanent systems are applied.
93. Instruments to measure support load include:
Answer: b)
Load monitoring verifies distribution and detects unexpected increases indicating instability.
94. Critical control for tailings used as fill is:
Answer: b)
Tailings can contain contaminants; containment, treatment and monitoring are essential for environmental safety.
95. Ensuring quality of rock bolts is done by:
Answer: b)
Testing ensures bolts are properly anchored and can transfer intended loads.
96. Renovating a deformed decline usually requires:
Answer: b)
Comprehensive re-support restores stability for safe vehicle and personnel access.
97. Role of ventilation during stowing is to:
Answer: b)
Ventilation management prevents worker exposure to hazardous dust and gases generated during filling.
98. Major cost drivers for stowing systems are:
Answer: b)
Logistics, plant, water handling and quality control significantly influence economics.
99. Support redundancy means:
Answer: b)
Redundancy improves safety by providing backup load paths if an element fails.
100. Final checks after stowing completion should include:
Answer: b)
Formal verification ensures the fill meets performance expectations and regulatory requirements.
101. The main purpose of backfilling in underground mines is to:
Answer: b)
Backfilling supports voids, stabilizes rock, and enables extraction of adjacent stopes.
102. Which support is widely used in metal mines for long-term stability?
Answer: b)
Steel arches provide reliable long-term support in permanent roadways.
103. The stability of paste fill depends heavily on:
Answer: b)
Binder percentage and curing control the final compressive strength of paste fill.
104. The major advantage of cable bolting over shorter rock bolts is:
Answer: b)
Cable bolts provide deep support essential for large or deep stopes.
105. Which stowing method avoids water completely?
Answer: b)
Pneumatic fill uses compressed air to blow dry fill material.
106. In high-stress mines, yielding supports are preferred because they:
Answer: b)
Yielding systems can handle dynamic loading safely.
107. Hydraulic stowing pipelines often fail due to:
Answer: b)
Sand slurry erodes pipes internally and forms blockages.
108. Steel supports are preferred in fire-prone zones because:
Answer: b)
Steel does not burn or emit gases under fire conditions.
109. In longwall mining, powered roof supports:
Answer: b)
PRS moves in sync with extraction, providing continuous roof support.
110. Which stowing method has highest density of compaction?
Answer: a)
Compressed air compacts material more densely than hydraulic fill.
111. Shotcrete is usually applied in thickness of:
Answer: b)
Shotcrete thickness typically ranges 50–75 mm depending on requirement.
112. Which is MOST important in selecting rock bolt length?
Answer: b)
Bolts must penetrate into competent rock to create stable reinforcement.
113. Paste fill reduces surface dumps by:
Answer: b)
Paste plants convert tailings into engineered underground fill.
114. Timber supports fail mainly because of:
Answer: b)
Biological degradation weakens timber drastically underground.
115. Cemented paste fill strength develops:
Answer: b)
Cement needs curing time (7–28 days) to reach full strength.
116. Which support is MOST effective for preventing local roof slabbing?
Answer: b)
Mesh and bolts keep surface slabs from detaching.
117. Stowing improves ventilation by:
Answer: b)
Filling voids reduces unwanted leakage and stabilizes airflow distribution.
118. Waste rock fill stability depends mainly on:
Answer: b)
Graded material compacts well and minimizes settlement.
119. Which one is a key safety requirement during hydraulic stowing?
Answer: b)
High-pressure pipelines can burst; exclusion zones are mandatory.
120. Timber chocks are preferred when:
Answer: b)
Timber chocks are economical and effective for short-term needs.
121. Rock bolt failure commonly occurs due to:
Answer: b)
Weak anchorage or overloading causes bolt pull-out or shear failure.
122. Paste fill plants require:
Answer: b)
Consistency of paste controls pumpability and final strength.
123. Underground void collapse risk increases if fill:
Answer: b)
Uncompacted fill leaves gaps leading to settlement and collapse.
124. Which support system is MOST commonly used in development tunnels?
Answer: b)
Bolts and mesh are fast to install and effective for temporary-to-permanent support.
125. Which condition requires very high-strength fill?
Answer: b)
High-strength artificial pillars (CPF) are required when mining near filled stopes.
126. In hydraulic stowing, free water must be controlled to:
Answer: b)
Excess water flow can wash material out and destabilize fill.
127. Which fill type provides least strength?
Answer: c)
Loose dry sand has minimal bonding and lowest compressive strength.
128. Major advantage of hydraulic stowing over dry fill:
Answer: b)
Slurry fills complex void geometry far better than dry fill.
129. Which is used as PRIMARY permanent support in haulage roadways?
Answer: b)
Long-term roadways require permanent, engineered support systems.
130. Which method reduces subsidence to the MINIMUM?
Answer: b)
Filling voids prevents downward movement of overburden.
131. Cable bolts are especially effective in:
Answer: b)
Cable bolts provide deep anchorage needed for large openings.
132. Stowing reduces fire risk in coal mines by:
Answer: b)
Filling voids reduces airflow and inhibits oxidation of coal remnants.
133. Which fill type can act as artificial pillars?
Answer: b)
CPF develops high strength to support adjacent workings.
134. Rock bolts primarily provide:
Answer: b)
Anchoring rock layers prevents separation and slab failure.
135. Critical environmental risk in hydraulic stowing is:
Answer: b)
Return water carries fines that must be treated before discharge.
136. For seismic mines, support must be:
Answer: b)
Yielding supports dissipate seismic energy and prevent sudden collapse.
137. Which process produces the most uniform fill?
Answer: b)
Paste is pumped and placed uniformly, eliminating large voids.
138. Rock bolts fail mainly due to:
Answer: b)
Under high stress, bolts shear or pull out if not properly anchored.
139. Stowing prevents pillar overloading by:
Answer: b)
Fill bears part of the load, reducing stress concentration on pillars.
140. Waste rock fill is MOST effective when:
Answer: b)
Layer-by-layer compaction increases stability and strength.
141. In longwall mines, goaf compaction helps in:
Answer: b)
Proper compaction controls caving and reduces stress on supports.
142. Timber cog supports are commonly used in:
Answer: a)
Cog supports are quick to install and suitable for short-term stability.
143. Fill stability improves when fines content is:
Answer: b)
Optimal fines fill voids between coarse particles improving packing.
144. Paste fill pumpability depends on:
Answer: b)
Excess solids make pumping difficult while low solids reduce strength.
145. For weak rock mass, support spacing should be:
Answer: b)
Closer spacing distributes load evenly and controls deformation.
146. Dry stowing is mainly used in:
Answer: b)
Manual/mechanical dry fill is convenient for narrow stopes.
147. Yielding steel props are used when:
Answer: b)
They deform safely under load, absorbing convergence energy.
148. Flyash stowing reduces:
Answer: b)
Flyash is a waste product; using it for fill reduces surface disposal burden.
149. Weak bedding planes require:
Answer: b)
Weak discontinuities need deeper anchoring and dense support patterns.
150. Stowing in coal mines mainly prevents:
Answer: b)
Stowing reduces air leakage into goaf and prevents surface subsidence.
151. Which monitoring device is used to measure displacement in rock?
Answer: b)
Extensometers measure relative movement or convergence between points in the rock mass.
152. What is the primary purpose of a grout curtain near a fill?
Answer: b)
Grout curtains are used to limit seepage paths and protect aquifers from contamination.
153. Which is a key sign of pipeline abrasion in slurry lines?
Answer: a)
Abrasion gradually thins pipe walls reducing capacity and risking leaks before total blockage.
154. Which protective measure reduces dust during dry/pneumatic stowing?
Answer: b)
Dust control via extraction and suppression protects workers and environment.
155. What is the usual test to check grout strength?
Answer: b)
Compressive testing verifies grout reaches design strength and permeability reduction targets.
156. Which structural element transfers roof load to the ground in longwall faces?
Answer: b)
Chocks carry the roof load and protect machinery and miners at the face.
157. Which is the best tracer to check slurry movement in pipelines?
Answer: b)
Flow meters and pressure signals provide objective data on pipeline movement and blockages.
158. What is an advantage of engineered fill over random waste fill?
Answer: b)
Engineered fills are processed and controlled to meet design specifications for strength and stability.
159. Which practice best reduces contamination risk from tailings used underground?
Answer: b)
Treatment ensures harmful elements are immobilized and environmental risk is reduced.
160. What is the benefit of staged filling?
Answer: b)
Staging helps manage consolidation, water release and quality control of fill.
161. Which instrument measures pore water pressure in fills?
Answer: b)
Piezometers monitor pore pressures that affect stability and piping risk.
162. Why are inspection records critical after bolting?
Answer: b)
Records prove compliance and help schedule maintenance or remedial work.
163. Which fill is least likely to be pumpable?
Answer: b)
Large boulders cannot pass through pumps or pipelines; pumpable fills are fine-grained or slurried.
164. What is the effect of high groundwater inflow into a stope during hydraulic filling?
Answer: b)
Uncontrolled water dilutes mixes and can create pathways for washout or contamination.
165. Which maintenance task reduces corrosion of steel supports?
Answer: a)
Coatings and cathodic systems extend service life by limiting corrosion.
166. Which practice improves paste fill homogeneity?
Answer: b)
Consistent plant control ensures uniform strength and pumpability.
167. In stoping operations, what is undercutting risk related to?
Answer: a)
Improper sequencing or removing support can cause collapse of the overlying rock.
168. What is the purpose of a packhouse or buffer tank in paste plants?
Answer: b)
Buffers even out production variations and maintain constant supply to pumps.
169. Which is the safest practice when draining a filled area?
Answer: b)
Controlled drainage prevents sudden changes that could induce instability or piping.
170. Which support measure helps manage rock bursts?
Answer: b)
Yielding systems absorb energy and destress blasting reduces stored strain energy.
171. Which is the main drawback of very high binder content in paste fill?
Answer: b)
Excess binder increases cost and may induce brittleness or shrinkage issues.
172. What reduces the likelihood of grout washout when constructing curtains?
Answer: b)
Controlled mixes and placement reduce washout and ensure barrier integrity.
173. Which is a common method to verify pipeline wear rate?
Answer: b)
Ultrasonic surveys track wall thinning and schedule replacements before failure.
174. What is the best practice when filling near existing utilities underground?
Answer: b)
Protecting utilities avoids damage and service interruptions; pressure control prevents blowouts.
175. Which is a typical remediation when a bolted face shows plate separation?
Answer: b)
Increasing reinforcement and surface confinement addresses slab detachment risks.
176. Which parameter is crucial for pump selection in paste systems?
Answer: b)
Pump must handle expected solids loading and rheology to avoid blockages and wear.
177. Which is a likely sign of impending roof collapse?
Answer: a)
Audible noises and increasing movements indicate failing rock mass and support overload.
178. Which approach helps reduce slurry settling in pipelines?
Answer: b)
Adequate velocity prevents deposition; additives improve suspension stability.
179. What action should follow detection of elevated pore pressures in a filled zone?
Answer: b)
High pore pressure may destabilize fill; remedial drainage and investigation are required.
180. Which is the safest way to handle a misfire in a stowed area?
Answer: b)
Safety protocols exist to manage misfires—never handle without qualified personnel and procedures.
181. Which support is best for short-span soft ground headings?
Answer: b)
Steel ribs adapt well to soft ground and short spans with rapid installation.
182. Which is a benefit of remote-operated bolting rigs?
Answer: b)
Remote rigs protect workers from loose rock and speed up installation.
183. What is the effect of too low solids concentration in paste fill?
Answer: b)
Too dilute mixes reduce strength and may segregate, reducing performance as support.
184. Which is an environmental advantage of underground backfilling?
Answer: b)
Backfilling returns waste underground, decreasing surface disposal and associated impacts.
185. Which material property best improves pumpability of paste?
Answer: b)
Controlled particle size and water content optimize rheology for pumping without segregation.
186. Which is a primary design goal for fill strength?
Answer: b)
Design strength ensures the fill can carry loads and maintain stability as planned.
187. Which method best identifies weak zones before excavation?
Answer: b)
Proactive investigation guides support design and reduces unexpected failures.
188. Which is a risk of over-compacting fill near sensitive structures?
Answer: a)
Over-compaction can increase stress transfer—design must consider adjacent structure capacity.
189. What is the effect of insufficient curing time on cemented fill?
Answer: a)
Curing allows hydration; inadequate curing means lower strength and susceptibility to degradation.
190. Which routine helps extend pipeline life?
Answer: b)
Proactive maintenance and protective linings reduce failures and downtime.
191. Which is the correct response to unexpected convergence in a heading?
Answer: b)
Safety-first approach: stabilize area and investigate cause before resuming operations.
192. Which is an indicator that paste fill mix is too stiff to pump?
Answer: b)
High pressures and blockages show rheology problems; mix adjustments or stronger pumps needed.
193. Which is a common maintenance for shotcrete surfaces?
Answer: a)
Inspections detect delamination and cracking which are then repaired to maintain integrity.
194. For environmental compliance, which is essential when using industrial byproducts as fill?
Answer: b)
Regulatory compliance requires testing to ensure no harmful leachates or environmental effects.
195. Which action improves safety during fill placement in confined areas?
Answer: b)
Remote methods and strict exclusion reduce occupational exposure and risk during placement.
196. Which is a common method to check grout curtain continuity?
Answer: b)
Testing assures the curtain is continuous and effective in reducing permeability.
197. Which is a practical reason to use dry waste rock fill?
Answer: a)
Dry backfill is practical where paste/pipeline infrastructure is not feasible, especially in narrow stopes.
198. Which is an emergency response after a pipeline burst underground?
Answer: b)
Stopping pumps and securing area prevents further flooding and hazard; repairs follow assessment.
199. Which monitoring helps detect early support overload?
Answer: b)
Instrumentation reveals rising loads allowing preemptive reinforcement or evacuation.
200. Final verification after completion of stowing should confirm:
Answer: b)
Complete verification ensures intended performance, environmental safety and regulatory compliance.
201. Which device detects early roof movement by measuring convergence?
Answer: b)
Extensometers measure distance changes between fixed points, indicating convergence or movement.
202. What is the main function of shotcrete mesh systems?
Answer: b)
Mesh plus shotcrete provides surface support and prevents small-scale spalling.
203. Which parameter most influences slurry pipeline wear?
Answer: b)
Coarse particles and high velocities increase abrasive wear on pipe interiors.
204. Which support is typically pre-tensioned to improve performance?
Answer: b)
Grouted and pre-tensioned bolts compress the rock mass and improve immediate support.
205. Best practice for controlling fill segregation is to:
Answer: b)
Controlled mix proportions and placement avoid segregation and assure uniform strength.
206. Which is a primary reason for choosing paste fill over hydraulic fill?
Answer: b)
Paste fill minimizes free water issues and produces higher strength after curing.
207. Which routine should be performed on bolting rigs to ensure quality?
Answer: b)
Equipment calibration and testing ensure bolts are installed to specified performance.
208. What is the effect of vibration from heavy equipment on supports?
Answer: b)
Repeated vibration can fatigue connections and lead to premature failure unless designed for it.
209. Which monitoring is most useful to detect fill piping?
Answer: b)
Rising pore pressures and unexpected settlements indicate piping and internal erosion.
210. Which support method is quickly deployable for emergency roof control?
Answer: b)
Timber cribbing and hydraulic packs can be installed rapidly to stabilize failing ground immediately.
211. Best way to reduce dust at pneumatic filling points is to:
Answer: b)
Enclosures and extraction capture dust at source preventing worker exposure and contamination.
212. Which is most likely to reduce pipeline blockages?
Answer: b)
Sustained velocities and mechanical cleaning prevent deposition and clear blockages.
213. Why is geotechnical mapping important before designing supports?
Answer: b)
Mapping defines geological features that control failure modes and appropriate support choice.
214. Which action improves the lifecycle of timber supports?
Answer: b)
Wood preservatives and dry conditions slow decay and extend timber life underground.
215. Which fill testing confirms particle grading for pumpability?
Answer: b)
PSD ensures the mix has appropriate fines and coarse content for stable pumping and placement.
216. Which factor is critical when placing fill close to public infrastructure?
Answer: b)
Controlling pressure prevents damage to nearby structures and ensures safe load transfer.
217. Which practice reduces methane migration from old workings?
Answer: b)
Filling and sealing prevents gas movement and reduces explosion/fire risk.
218. Which is a benefit of using industrial byproducts as fill?
Answer: b)
Repurposing byproducts reduces environmental footprint provided they are safe and approved.
219. Which is critical to prevent induced seismicity during stowing?
Answer: b)
Slow, monitored filling avoids rapid stress changes that can trigger seismic events.
220. What is the desired outcome of grout curtain verification?
Answer: b)
Verification ensures the curtain forms an effective barrier preventing unwanted flow paths.
221. Which is the best control for flyash dust during handling?
Answer: b)
Containment and filtration reduce worker exposure and environmental emissions.
222. Which fill testing confirms environmental safety?
Answer: b)
Chemical testing ensures no harmful species will migrate into groundwater or environment.
223. What action reduces clogging in intake screens for slurry plants?
Answer: b)
Proper screening and maintenance prevent large particles entering pumps causing blockages.
224. Which support strategy reduces risk in highly fractured rock?
Answer: b)
Close spacing and deeper anchors better control movement in fractured masses.
225. Which is essential before re-entering a newly filled stope?
Answer: b)
Verification ensures that the fill has attained sufficient stability and strength for safe access.
226. Which is a sign of grout segregation during placement?
Answer: b)
Segregation leads to uneven strength and potential weak zones within the curtain or fill.
227. Which component is important for paste pump maintenance?
Answer: b)
Seals and valves undergo wear due to abrasive slurries and must be maintained to prevent failures.
228. Which is a good indicator that a fill has achieved design strength?
Answer: b)
Lab compressive tests provide objective confirmation that the fill meets strength requirements.
229. Which operational change can reduce pipe abrasion rates?
Answer: b)
Operating within recommended velocities and reducing coarse loads slows abrasive wear.
230. Which is a practical method to handle surplus tailings if paste plant not available?
Answer: b)
If underground reuse is impossible, proper tailings storage facilities with controls are required.
231. Which is a common cause of grout curtain failure?
Answer: b)
Incomplete filling, improper mix or washout compromise curtain continuity and effectiveness.
232. Which inspection is vital after installing shotcrete?
Answer: b)
Ensuring full adhesion and adequate thickness prevents early failure of the shotcrete layer.
233. Which practice mitigates risk when pumping paste long-distance?
Answer: b)
Intermediate boosters, pressure control and flushing maintain flow and allow rapid clearing if needed.
234. What is an advantage of mechanised backfilling operations?
Answer: b)
Mechanisation delivers uniform placement and increases safety by distancing workers from hazards.
235. Which is essential when designing support for a major intersection?
Answer: b)
Intersections face higher loads and need robust, redundant support systems to ensure safety and access.
236. Which is a proactive step to prevent pipeline freezing in cold climates?
Answer: b)
Insulation and heating preserve slurry temperature and prevent blockages due to freezing.
237. What is the effect of inadequate compaction on paved haulage road above backfill?
Answer: b)
Poorly compacted fill cannot support surface loads leading to deformation and costly repairs.
238. Which is a common safety control during bolting operations?
Answer: b)
Controls protect workers from rockfalls, tool hazards and ensure safe work coordination.
239. Which is an operational sign that a paste mix is segregating?
Answer: b)
Segregation causes inconsistent rheology and visible bleed which affect pumpability and strength.
240. Which is essential to protect groundwater when using industrial fill?
Answer: b)
Monitoring wells and leach tests confirm that contaminants are not migrating into groundwater.
241. Which is a likely consequence of over-pressurising a stope during filling?
Answer: b)
Excessive pressures can create new pathways, fractures or piping leading to failures.
242. Which fill type is least environmentally risky when properly treated?
Answer: a)
Cementation immobilizes contaminants and reduces leaching risks when designed correctly.
243. Which factor most affects long-term performance of support steels?
Answer: b)
Corrosion control, coatings and regular inspections are crucial for preserving strength and safety.
244. Which is a reason to use staged dewatering of a filled area?
Answer: b)
Controlled dewatering prevents piping and sudden stress redistribution that can cause failure.
245. Which is a necessary step after detecting increased support loads?
Answer: b)
Prompt investigation and remediation prevents progressive failure and preserves safety.
246. Which is an immediate measure when a pipeline section bursts?
Answer: b)
Isolation and stopping pumps prevents further flooding and reduces hazard while repairs are planned.
247. Which is the best practice to manage reclaimed water from settling ponds?
Answer: b)
Recycling treated water reduces fresh water use and environmental discharge impacts.
248. Which monitoring would indicate accelerated degradation of a steel arch?
Answer: b)
Ultrasonic wall thickness surveys and corrosion monitoring reveal loss of capacity before failure.
249. Which is the most reliable sign of adequate fill consolidation?
Answer: b)
Predictable settlement plateau and instrument confirmation show the fill has consolidated as designed.
250. Final documentation after a stowing project should include:
Answer: b)
Complete records are essential for safety validation, future reference and regulatory compliance.
