20mm Fiberglass Rock Bolt

Specifications and Characteristics

The 20 mm fiberglass rock bolt is a pultruded composite ground-support element. Typical dimensional and material characteristics are summarized below:

• Diameter: 20 mm (approximately 3/4 inch)
• Material: Fiberglass reinforced with E-glass fibers
• Resin Type: Polyester or epoxy resin
• Glass Content: Not less than 75% by weight
• Thread Type: Right-hand threads

Performance Characteristics

The 20 mm fiberglass rock bolt is manufactured by continuous pultrusion, aligning E-glass rovings longitudinally in a thermoset resin matrix. Typical mechanical values include:

• Tensile Strength: Minimum 31,500 lbs (140 kN)
• Shear Strength: Minimum 6,200 lbs (28 kN)
• Nut/Thread Strength: Minimum 18,000 lbs (80 kN)
• Elastic Modulus (E-Modulus): Minimum 5,075 ksi (35,000 MPa)
• Breaking Strain: Maximum 3%

Applications and Advantages

Fiberglass rock bolts, including the 20 mm diameter, are widely used in mining and tunneling. Common operational advantages over traditional steel bolts include:

1. Ease of Excavation: Fiberglass bolts can be cut during subsequent excavation work without damaging cutter heads.
2. Safety: They eliminate sparks, reducing ignition risk in potentially explosive environments.
3. Reduced Equipment Damage: They cause less damage to conveyors, chains, and other equipment than steel bolts.
4. Workflow Efficiency: They minimize interruptions due to bolt-related issues such as conveyor belt tears or chute blockages.
5. No Hot Work Required: No need to cut steel bolts from cutter heads, reducing the need for hot work permits.

For a broader overview of composite reinforcement, see our FRP rebar and pultruded profiles pages. Our pultrusion machines and pultrusion dies support custom manufacturing of rock bolt geometries and resin systems.

Additional Components

The fiberglass rock bolt system typically includes:

• Nut Size: 1.65 inches inner diameter x 3.1 inches long (42 mm inner diameter x 80 mm), for 20 mm bolts.
• Fiberglass Plate: 4.7 inches square x 3/4 inch thick (120 mm square x 20 mm thick).

FAQ

What is the tensile strength of a 20mm fiberglass rock bolt?

A 20 mm fiberglass rock bolt typically provides a minimum tensile load of 31,500 lbs (140 kN). This makes it suitable for demanding tunnel, mine, and slope support applications.

What is the shear strength of a 20mm fiberglass rock bolt?

A 20 mm fiberglass rock bolt offers a minimum shear strength of 6,200 lbs (28 kN), providing reliable performance under lateral forces common in rock mass stabilization.

Why use a 20mm fiberglass rock bolt instead of steel?

A 20 mm fiberglass rock bolt is non-corrosive, approximately 75% lighter than an equivalent-diameter steel bolt by weight, fully cuttable by TBMs, and electrically non-conductive. It reduces corrosion concerns, handling costs, and equipment damage during mechanized excavation.

What are the dimensions of a 20mm fiberglass rock bolt?

A 20 mm fiberglass rock bolt has a nominal diameter of 20 mm (0.79 inches) with standard lengths from 1.4 m to 6 m. The threaded nut/thread section provides a minimum strength of 18,000 lbs (80 kN).

How is a 20mm fiberglass rock bolt installed?

Drill the hole to the required depth, insert the bolt with a resin cartridge, rotate 10-15 seconds to mix the resin, allow curing time (typically 30-60 seconds), then tension with a plate and nut. Installation uses standard bolting equipment.

What applications use 20mm fiberglass rock bolts?

20 mm fiberglass rock bolts are used for tunnel face bolting, mine roof and wall support, slope stabilization, retaining walls, and foundation improvement in mining, tunneling, and civil engineering projects.

Is a 20mm fiberglass rock bolt corrosion resistant?

Yes. The glass-fiber and thermoset resin matrix resists corrosion from water, chemicals, and soil conditions commonly encountered in underground environments.

Can a 20mm fiberglass rock bolt be cut by a TBM?

Yes. A 20 mm fiberglass rock bolt can be cut by tunnel boring machine cutters without the tooling damage often associated with steel bolts.

For other diameters and application guidance across mining and tunnel projects, visit our fiberglass rock bolt systems overview.