A complete guide on types of supports in mining and stowing methods. Learn steel supports, timber supports, powered supports, hydraulic props, sand stowing, hydraulic stowing, pneumatic stowing, and DGMS guidelines. Updated for 2026.

Underground mining is one of the most complex engineering operations. As the ore is extracted, the void created must be safely supported to prevent roof collapse, pillar failure, sidewall movement and overall instability. The two most important activities that determine the safety of an underground mine are:

1. Support Systems
2. Stowing Operations

Together, they ensure that miners, equipment, and underground openings remain safe and stable throughout the life of the mine.

This guide explains every type of mine support, its application, advantages, limitations, and stowing methods used in metalliferous and coal mines — specifically for DGMS, Royalty inspector, Mine Supervisor, mining diploma and competitive exams.

What Are Mine Supports?

Mine supports are structural elements installed in underground workings to maintain the opening created by excavation. Their purpose is to:

• Hold up the roof
• Prevent sidewall collapse
• Reduce convergence
• Control stress redistribution
• Create safe travel and working routes
• Maintain long-term stability

Classification of Mine Supports

Mining supports can be divided into two major categories:

A) Temporary Supports

Used during development when the area is not permanent.

B) Permanent Supports

Installed in stopes, main haulage roadways, and long-term workings.

Further classification:

1. Timber Supports
2. Steel Supports
3. Powered / Hydraulic Supports
4. Friction / Yielding Props
5. Cable Bolts & Rock Bolts
6. Concrete & Masonry Supports
7. Packwalls / Stone Packs / Goaf Supports

In this article we will explore each in detail.

Timber Supports in Mining

Timber is the oldest and most widely used supporting material. Its flexibility, availability, and ease of use make it ideal for small mines and development headings.

Common Timber Supports:

1. Timber Props
2. Crossbars
3. Chocks
4. Cog Supports (4-leg supports)
5. Timber Packs
6. Split Sets

Advantages of Timber:

• Absorbs shock loads
• Flexible and yielding
• Provides warning before failure (creaking sound)
• Lightweight and easy to transport
• Easy installation and removal

Disadvantages:

• Subject to rot, moisture, and insect damage
• Limited strength compared to steel
• Bulky and space consuming
• Not suitable in deep and highly stressed mines

Where Timber is Used:

• Development headings
• Bord & pillar coal mines
• Soft rock formations
• Temporary supports

Steel Supports in Mining

Steel supports replaced timber because of higher strength, longer life, and resistance to environmental damage.

The major steel supports used are:

A) Steel Props

• High compressive strength
• Often hydraulic or friction based

B) Steel Ribs / Steel Arches (V-Arches)

Used in:

• Permanent roadways
• Highly stressed openings
• Wet conditions

C) Steel Chocks

Steel frames used in longwall mining.

D) I-Beam and H-Beam Supports

Used in metalliferous mines and tunnels.

Advantages of Steel Supports:

• High load-bearing capacity
• Long life
• Fire resistant
• Easy to install in segments

Disadvantages:

• Higher cost
• Corrosion risk
• Needs skilled labor

Powered Supports (Hydraulic / Powered Roof Supports)

Modern longwall mines use Powered Roof Supports (PRS), also known as Hydraulic Shields.

Types:

• Chock Shield
• Cloak Shield
• Shield Supports
• Unit Supports

Characteristics:

• Fully mechanized
• Operate using hydraulic pressure
• Immediate roof support after cutting cycle
• Used in high-production longwall panels

Advantages:

• Very high capacity
• Fast movement
• Allows continuous cutting operations
• Safer for workers

Disadvantages:

• Expensive
• Requires skilled maintenance
• Needs compatible longwall equipment

Rock Bolting Systems

Rock bolts are now the primary support system in most underground metal mines.

Types of Rock Bolts:

1. Mechanical roof bolts
2. Resin-grouted bolts
3. Cable bolts (for deep and wide spans)
4. Split set stabilizers
5. Swellex bolts

Why rock bolts?

• Bind fractured rock layers together
• Create a ‘self-supporting arch’
• Reduce need for timber/steel supports
• Faster installation
• Cost-effective

Concrete & Shotcrete Supports

Shotcrete is cement mortar sprayed at high speed on the walls and roof.

Benefits:

• Prevents loose rock fall
• Controls scaling
• Long-term stability
• Used with rock bolts for composite support

Packwalls / Goaf Supports

Goaf areas (caved roof behind longwall face) require pack supports.

Types:

• Stone packs
• Sand packs
• Hydraulic sand stowing
• Concrete packs

These prevent roof from collapsing into main roadway.

What is Stowing in Mining?

Stowing is the practice of filling the voids (goaf/stopes) created by underground mining with suitable material to:

• Support the roof
• Prevent subsidence
• Reduce surface cracks
• Control water flow
• Maintain stability of pillars

Stowing is essential in both coal and metal mines, especially where:

• The overburden is weak
• Pillars are small
• Extraction ratio is high
• Urban or sensitive structures exist above the mine
• Subsidence is not acceptable

Stowing is also mandatory in areas where accumulation of caved material may lead to spontaneous combustion (coal mines).

10. Objectives of Stowing

1. Prevent or reduce surface subsidence
2. Increase extraction percentage
3. Reduce load on standing pillars
4. Ensure roof stability
5. Control air leakage in goaf
6. Prevent fires in coal mines
7. Provide safe working environment
8. Avoid collapse of shafts and roadways

These objectives are critical in longwall coal mining and cut-and-fill methods of metal mining.

Requirements of Good Stowing Material

A good stowing material must have:

• Flowability: So it can move easily into stopes/goaf.
• Adequate strength: To bear the weight of the strata.
• Non-hazardous nature: Should not produce poisonous gases.
• Affordable and readily available
• Minimal environmental impact

Types of Stowing Used in Mining

Stowing can be classified into:

A) Hydraulic Stowing

B) Pneumatic Stowing

C) Sand Stowing

D) Flyash Stowing

E) Waste Rock Backfilling

F) Paste Fill / Cemented Paste Fill

G) Dry Stowing (Hand-filled / mechanical)

Let us understand each in detail.

Hydraulic Stowing (Sand & Slurry Stowing)

Hydraulic stowing is one of the most widely used methods in India, especially in coal mines.

Process:

1. Sand/flyash is mixed with water.
2. The slurry is transported through pipes.
3. It flows into the void space.
4. Water drains out, leaving solids behind.

Equipment Required:

• Sand bunkers
• Vibrating screens
• Pumps
• Pipes (steel/rubber)
• Settling tanks
• Drainage system

Advantages:

• Excellent flowability
• Fills remote/irregular voids
• Reduces surface subsidence
• Allows high extraction ratio
• Cost-effective

Disadvantages:

• Requires large water supply
• Risk of pipeline choking
• Not suitable in steep seams

Best Applied In:

• Coal mines
• Shallow depth workings
• Areas with surface structures

Pneumatic Stowing

Pneumatic stowing uses compressed air to blow dry material (sand, crushed stone, ROM) into the stopes.

Process:

1. Dry material is fed into a stowing hopper.
2. Compressed air forces it through pipes.
3. Material is packed tightly into the stopes.

Advantages:

• Very dense packing
• No water required
• Ideal for steep seams or inclined workings
• Faster filling

Disadvantages:

• Requires expensive compressor systems
• Produces dust
• Higher operating costs

Sand Stowing

Used in coal mines for many decades.

Properties of good sand:

• Grain size 1–3 mm
• Clean & free from clay
• All-round packing capability

Source:

• River sand
• Desert sand
• Manufactured sand

Sand is still one of the best stowing materials due to its flowability and affordability.

Flyash Stowing

Flyash is a byproduct of thermal power plants.

Why use flyash?

• Easily available
• Low cost
• Environmentally beneficial
• Good flow properties

Issues to consider:

• Requires controlled dumping
• Reacts with water
• May require cement addition

Waste Rock Backfilling

Hard rock metal mines generate large volumes of waste rock.

Instead of dumping it on the surface, mines use waste rock to backfill stopes.

Advantages:

• Eco-friendly
• Cost-efficient
• Increases extraction ratio
• Reduces surface dump heaps

Materials used:

• Waste rock
• Crusher fines
• Mill tailings

Paste Fill / Cemented Paste Fill (CPF)

Modern metal mines use cemented paste fill, especially in deep mines.

Composition:

• Tailings (0–2 mm)
• Cement binder
• Water

Advantages:

• Very high compressive strength
• Creates artificial pillars
• Allows 90–95% extraction
• Excellent stability

Used In:

• Cut-and-fill stopes
• Longhole open stoping
• Deep underground metal mines

Dry Stowing

Oldest method — stowing is done manually or mechanically without water.

Methods:

• Hand packing
• Scraper loading
• Payloader dumping

Not widely used today except in:

• Narrow veins
• Small metal mines
• Villager-operated mines

Stowing Cycle (Step-by-Step Process)

1. Goaf/void creation
2. Stowing pipe installation
3. Material preparation (sand/flyash/tailings)
4. Transport to stowing area
5. Feeding into pipes/hoppers
6. Flowing into void
7. Drainage of water (in hydraulic stowing)
8. Compaction
9. Testing and monitoring

DGMS Rules for Stowing in Mines (VERY IMPORTANT)

DGMS mandates strict guidelines for stowing operations:

1.Stowing must be carried out where:

• There is risk of subsidence
• Extraction ratio is high
• Surface structures exist
• Fire risk is high
• Pillars are weak

2. Water used in hydraulic stowing must be non-corrosive.

3. All pipelines must be pressure-tested and leak-proof.

4. Stowing must not obstruct ventilation.

5. Proper supervision must be maintained during the entire cycle.

6. Daily stowing logbook must be maintained.

7. Stowing must follow approved Mine Plan & legislation.

8. Stowing material must not contain toxic substances.

9. Excessive water discharge must be prevented.

10. All stowing workers must wear PPE.

Advantages of Stowing

• Prevents surface subsidence
• Allows higher extraction (up to 85–95%)
• Improves overall mine safety
• Reduces air leakage in goaf
• Prevents spontaneous combustion
• Supports weak roofs
• Improves stability of pillars, galleries, raises

Disadvantages of Stowing

• Expensive (cemented paste fill)
• Requires water (for hydraulic)
• Equipment heavy
• Pipeline choking issues
• Requires continuous monitoring

Applications of Stowing in Mining

Coal Mines (Bord & Pillar + Longwall)

• Sand stowing
• Pneumatic stowing
• Flyash stowing

Metal Mines

• Waste rock backfill
• Paste fill
• Hydraulic fill

Deep and High-Stress Mines

• Cemented paste fill
• Cable bolting + fill

Conclusion Of Types Of Supports and Stowing In Mining

Mining supports and stowing are the foundation of underground safety. Timber, steel, hydraulic supports, powered supports, rock bolts, and shotcrete stabilize openings. Stowing — whether sand, hydraulic, pneumatic, waste rock, or paste fill — ensures long-term stability, prevents subsidence, controls fires, and increases extraction.