Rock stresses around a tunnel opening are redistributed once excavated. Rock joints, fractures, groundwater or disturbance from construction can create varying conditions throughout the tunnel alignment.
Common problems include:
– Fractured or loose rock surrounding the tunnel crown and sidewalls
– Local block failures or rock spalling
– Overbreak due to blast damage or changing geologic conditions
– Stress-induced deformation surrounding the excavation
– Faults, shear zones, and extremely jointed rock masses
– Water inflow or corrosive ground conditions
– Irregular tunnel profiles or uneven borehole conditions
– Limited access for installation close to the tunnel face
– Time-sensitive applications for rapid installation of support
– Longevity of support performance through the entire service life
– Mix of materials between bolts, plates, mesh, straps and shotcrete
– Difference between temporary and long-term support designs
Rock and ground conditions should be regularly reviewed during excavation as support requirements may change when new geologic conditions are uncovered.
Wanfeng offers rock reinforcement and surface- retention products that work together to provide a comprehensive tunnel ground-control solution. Rock bolts and threaded rock reinforcement bars can be used to stabilize fractured or potentially unstable rock against sounder rockmass behind the tunnel face. Bearing plates help spread bearing pressures at the tunnel face. Welded wire mesh and steel straps can be used to help retain smaller, loose fragments between points of reinforcement. When required by the engineer, these products can also be used in conjunction with shotcrete, lattice girders or other primary-support systems.
Ideally, the final ground- support solution will:
• Reinforce jointed/fractured rock around the excavation
• Restrain loose rock between bolt positions
• Spread point loads across a greater surface area
• Allow for better integration of reinforcement with surface retention products
• Allow for efficient installation as tunneling progresses
• Include product configurations designed for the environment into which they are exposed.
Engineering disclaimer
Engineering final product selection, bolt pattern, spacing, length, method of anchorage, installation procedure and tunnel support design must be carried out by a registered geotechnical, geological, tunnelling or structural engineer who can take into account factors such as site investigation, tunnel geometry, groundwater, method of construction, design life and all applicable codes of practice.
Wanfeng can only supply products to confirmed specifications and do not assume any responsibility for the design of ground-support.
1. Rock Bolts / Tunnel Bolts
Steel local or systematic reinforcement components installed around tunnel crowns, shoulders and sidewalls.
Important Specification Fields:
Diameter
Length
Steel
Yield & Ultimate Strength
Additional Specification Options:
Thread Style
Anchorages
Surface Coating
2. Fully Grouted Threaded Rebar Bolts
Threaded bars typically specified for full-column grout or resin installations per approved tunnel support designs.
Important Specification Fields:
Bar Diameter
Available Lengths
Yield Strength
Ultimate Load Capacity
Additional Specification Options:
Thread Direction and Pitch
Coupler Style
Corrosion Protection Options
3. Friction Bolts / Split Sets
Friction-type rockbolts designed for rapid installation when allowed by borehole diameter, rock conditions and approved tunnel support designs.
Important Specification Fields:
Tube Diameter
Bolt Length
Steel Grade
Nominal Load Rating
Additional Specification Options:
Ring Style
Surface Coating
Suggested Borehole Size Range
4. Cable Bolts
Long anchorages that can be used when reinforcement or anchorage past the immediate tunnel perimeter is needed.
Important Specification Fields:
Cable Diameter
Length
Strand Count
Min Breaking Strength
Additional Specification Options
Number of Bulbs
Number of Grout Bulbs
Corrosion Protection
5. Bearing Plates
Steel plates used with compatible bolts/nuts to help spread load against rock or other supported surface.
Important Specification Fields:
Dimensions
Thickness
Diameter of holes
Material
Additional Specification Options:
Flat or Domed
Load Capacity
Surface Coating
6. Welded Wire Mesh
Mesh used between bolts to help control smaller loose rocks and support the installed tunnel surface reinforcement.
Important Specification Fields:
Wire Diameter
Mesh Opening Size
Panel Size
Weld Size
Additional Specification Options
Type of Edge Wire
Hot Dip Galvanized or Green
Overlap requirements
7. Steel Straps
Components that help distribute loads and support surfaces that can be installed between bolts in jointed or blocky rock conditions.
Important Specification Fields:
Width
Material Thickness
Length
Spaced/Bushings
Additional Specification Options:
Style
Material
Surface Coating
8. Nuts, Couplers and Accessories
Steel accessories used with compatible bolts. Normally installed per required thread style, installation method and load requirements.
Important Specification Fields:
Thread Size and Type
Size / Dimensions
Material
Surface Treatment
Available Options Include:
Nut
Coupler
Washer
Centralizers
Spacer
Installation Aid Kit
| Typical ground or construction condition | Typical support requirement | Product categories that may be relevant |
| Competent rock with isolated loose blocks | Localized reinforcement | Rock bolts with bearing plates |
| Jointed crown or sidewalls | Reinforcement and surface retention | Rock bolts with welded wire mesh |
| Blocky or fractured rock | Load distribution between reinforcement points | Threaded bolts with mesh and steel straps |
| Irregular excavation surface or overbreak | Improved surface coverage and adaptable retention | Bolts with overlapping mesh panels and suitable plates |
| Weak or variable rock zones | More continuous reinforcement and surface control | Fully grouted threaded bolts with mesh; additional support as designed |
| Deeper potentially unstable rock mass | Reinforcement beyond the immediate excavation boundary | Longer rock bolts or cable bolts where verified by the engineer |
| Rapid tunnel advance | Efficient installation using compatible components | Friction bolts or other approved rapid-installation systems |
| Wet or chemically aggressive conditions | Project-defined corrosion resistance | Galvanized, coated or otherwise protected components |
| Temporary initial support | Installation speed and compatibility with excavation sequence | Bolts, plates, mesh and straps selected for the approved sequence |
| Long design life or permanent support | Durability, traceability and corrosion protection | Verified permanent-support products with documented protection |
| High deformation, seismic or dynamic loading | Deformation or energy-absorption capacity | Only products with verified test data for the required loading condition |
Selection note
This matrix should be used for preliminary reference purposes only. While some of the listed products may be applicable under certain circumstances, this list should not be used as a standard for tunnel support selection. Bolt spacing, diameter, embedment length, grout/resin, preload, corrosion coatings, and installation testing are just a few of the decisions that must be made when engineering a project specifically.
Wanfeng can customize production according to the approved specification, drawing and production capacity.
Customization options may include:
Please confirm all customized dimension,tolerance,material&performance specifications on approved quotation &tech.drawings before production.
Manufacturing and Quality Control Effective quality-control requirements vary based on the product type, project specification and applicable inspection plan listed below.
1. Raw Material Inspection
Material certificate review
Chemical composition (as required)
Steel grade / heat-number identification
Incoming material dimensions
2. Dimensional and Thread Inspection
Diameter and length measurement
Thread profile / pitch inspection
Threaded- length verification
Plate / hole and mesh-aperture measurement
Coupler / nut fit checks
3. Mechanical Testing (Where applicable and contractually specified)
Tensile test
Yield / Ultimate Strength verification
Elongation test
Load test of component
Weld shear / weld-strength testing
Project-specific sample or batch mechanical testing
4. Surface Treatment Control
Visual inspection prior to and after treatment
Measurement of coating thickness (where specified)
Coating coverage and adhesion
Protection of threads / mating surfaces
Packaging controls to minimize damage during transport
5. Traceability and Final Inspection
Batch / heat number identification
Inspection certification
Quantity verification
Product marking
Packaging inspection
Shipping document review
Documentation should include the statement shown below.
Where certification or third party testing is required, the relevant cert number, issuing body, test report number, applicable product, and valid scope should be listed together. ASTM, EN, ISO, AS/NZS, or project specified standards should only be referenced if able to demonstrate conformity to the specific product supplied.
Provide us with as much of the following information as possible so we can evaluate your needs.
1.Q: What products are available for tunnel roof and wall reinforcement?
Ans: The combination of tunnel reinforcement components may vary based on ground conditions and support design. Possibilities include rock bolts, fully grouted threaded bars, friction bolts, bearing plates, welded wire mesh, steel straps and accessories. Each project should have a finalized combination specified or approved by the engineer of the project.
2.Q: How do rock bolts and steel mesh work together?
Ans: The rock bolts reinforce the rock mass and provide anchorage points along the surface of excavation. The mesh retains smaller loose pieces of rock between bolt lines or anchorages. Bearing plates and straps may increase load distribution and assure contact between mesh and supported structure.
3.Q:Can special sizes be made?
Ans: Non-standard diameters, lengths, threads and plate configurations can be produced when allowable by material, tooling and production capacity and order quantity. Please provide the required dimensions, associated loads, tolerances and drawings for evaluation.
4.Q: What surface treatment should be used for wet tunnels?
Ans: Possible treatments include bare steel, hot dip galvanizing or other specified coating processes. Consideration should be given to groundwater chemistry, expected service life, damage during installation, design life and coating compatibility with grout, resin and other support materials.
5.Q: How do I select bolt diameter and length?
Ans: The correct size tunnel bolt depends on tunnel size and shape, discontinuity pattern, rock- mass quality, likely failure mode and many other considerations including load, borehole condition and required anchorage. A professional tunnel designer or geotechnical engineer should select these parameters.
6.Q:Can Wanfeng fabricate directly from project drawings?
Ans: Project drawings can be reviewed to verify if production is possible. The project specification should include materials, dimensions, tolerances, threads, mechanical properties, surface treatment, quality document and standards. Understand proper steps have been taken before starting production.
7.Q:Can the products be used with Shotcrete?
Ans: Rock bolts, plates and mesh are commonly used in tunnel primary-support systems which include shotcrete. Define accessory compatibility, installation order, cover requirements, bond strength and structural design in the project plans.
8.Q: What information is required to give me a quote?
Ans: Provide information such as the type of product, dimensions, steel grade, mechanical properties, surface treatment, quantity, standard, inspection documents, engineering drawings, destination for delivery, delivery schedule and other requirements. Geological information can be provided when you need our help to select products.
