Exposed ground conditions will rarely react as a single intact material. Depending on orientation of joints and rock structure, sequence of excavation, groundwater inflow, blasting damage, stress redistribution or time-dependent effects, behaviour may alter considerably.
Some typical problems are:
For this reason inspection, monitoring and verification of support should continue throughout construction and operation.
Wanfeng offers products used in rock-reinforcement and surface- retention as part of an overall ground-control solution. Rock bolts and threaded bars may be used to anchor unstable blocks into better quality rock mass outside the immediate excavation area. Bearing plates and steel straps are used to spread applied loads across the surface. Welded wire mesh is used to retain small rocks between the bolts.
These steel elements may also be used in conjunction with grout, resin, shotcrete, lattice girders, steel sets, cable reinforcement or other measures where required by the design engineer.
Together these parts are used to:
Engineering Disclaimer
The selection of the final support solution including product type, spacing, length, anchorage method, grout/resin selection, installation sequence/support capacity and monitoring must be completed or reviewed by a suitably qualified geotechnical, mining, tunnelling or structural engineer. This should take into consideration site investigation, rock mass classification, joint/settlement geometry, groundwater inflow, in-situ stress, excavation method, likely deformation rates, required design life and any governing standards.
Wanfeng can only supply ground support components to confirmed specifications and do not assume the responsibility of the engineer of record for ground-support design.
1. Rock Bolts
Steel bolts that can be utilized for spot or systematic support of broken rock near underground openings.
Important fields
• Diameter
• Length
• Steel grade
• Yield and ultimate loads
Other fields
• Thread form
• Anchorage type
• Surface coating
• Compatible plates
2. Fully Grouted Threaded Rebar Bolts
Threaded bars designed to be anchored in grout or resin for applications that need continuous grout or resin bonding along the shaft specified in the design.
Important fields
• Bar diameter
• Bar length
• Yield strength
• Ultimate tensile strength
Other fields
• Thread orientation and pitch
• Threaded portion
• Coupler compatibility
• Corrosion protection options
3. Friction Bolts / Split Sets
Split set style anchors that are engineered to be installed quickly by friction against the borehole wall.
Important fields
• Tube diameter
• Length
• Steel grade
• Nominal load rating
Other fields
• Ring configuration
• Surface coating
• Recommended drilling range
• Installation tooling requirements
Note
Performance of friction bolts is highly affected by borehole diameter, condition of rock, quality of installation and product dimensions. Use in squeezing ground, very enlarged holes or where diameters may change under stress should be confirmed prior to installation.
4. Cable Bolts
Longer length bolts that can be utilized when encountering unstable areas that may extend beyond regular bolt anchorages.
Important fields
• Cable diameter
• Cable length
• Strand configuration
• Minimum breaking strength
Other fields
• Bulb/bird cage style
• Grout pocket style
• Bonded length needed
• Corrosion protection
5. Bearing Plates
Plates used along with compatible bolts and nuts to help spread out loads and limit movement around the collar of the bolt.
Important fields
• Plate size
• Plate thickness
• Hole size
• Steel grade
Other fields
• Flat or curved style
• Load rating
• Washer needed
• Surface coating
Note
Sizes and stiffness of plates should be based on what surface conditions and loads are expected. If the plate is too small or not stiff enough it can create a high stress area in poor surface materials.
6. Welded Wire Mesh
Mesh that can be used on the surface to help prevent small loose rocks between support elements from falling.
Important fields
• Wire diameter
• Opening size
• Mesh size
• Weld strength
Other fields
• Type of edge wire
• Overlap needs
• Zinc coated or uncoated
• Compatibility with plates
7. Steel Straps
Steel straps can help spread out loads between bolts and limit movement along joints.
Important fields
• Width
• Thickness
• Length
• Hole pattern
Other fields
• Strap style
• Steel grade
• Hole size
• Surface coating
8. Nuts, Couplers and Accessories
Pieces that work with the threads on the bolt, design installation method and required strength.
Important fields
• Bolt thread and size
• Nut or coupler size
• Steel grade
• Surface treatment
Can also include
• Nuts
• Couplers
• Washers
• Centralizers
• Spacers
• Tooling
| Typical ground condition | Typical support requirement | Product categories that may be relevant |
| Competent rock containing isolated loose blocks | Localized block reinforcement | Rock bolts with bearing plates |
| Jointed or blocky rock | Reinforcement across discontinuities | Rock bolts or threaded bolts with suitable bearing plates |
| Fractured roof or sidewalls | Reinforcement and continuous surface retention | Bolts with welded wire mesh |
| Closely fractured surface rock | Control of smaller fragments between bolts | Welded mesh with plates and approved fasteners |
| Weak surface material around bolt collars | Wider load distribution | Larger or stiffer bearing plates and steel straps, subject to design |
| Alternating weak and competent layers | Reinforcement through the weak zone into suitable anchorage material | Longer threaded bolts or cable bolts where verified |
| Fault or shear zone | Continuous support and load distribution | Fully grouted bolts, mesh and straps as part of an engineered system |
| Irregular or overbroken excavation profile | Flexible surface coverage | Overlapping mesh panels with suitable plates and fasteners |
| Variable but stable boreholes | Installation system tolerant of defined hole variation | Only bolt systems verified for the measured borehole range |
| Boreholes prone to collapse | An anchorage and installation method suited to poor hole stability | Project-designed grouted, cased or alternative systems |
| Wet or corrosive conditions | Defined corrosion resistance | Galvanized, coated or otherwise protected components |
| Deep unstable zone | Reinforcement beyond the immediate excavation boundary | Longer bolts or cable bolts where engineering analysis confirms suitability |
| Squeezing or time-dependent ground | Deformation-compatible support | Only verified yielding or deformable products within an engineered system |
| Seismic or dynamic loading | Verified energy absorption and dynamic capacity | Only products supported by relevant dynamic test data |
| Long-term or permanent support | Durability, traceability and documented protection | Products with verified mechanical and corrosion-performance documentation |
Selection Disclaimer
This table should be used for preliminary reference purposes only. While some of the products shown may be applicable under certain conditions, they should not be considered to be suitable for all types of poor or jointed rock masses.
Bolt type, spacing, length, preload, grout or resin, mesh strength, corrosion protection and installation testing should be determined on a project specific basis and verified in the field.
Customization of Ground Support Products
All custom sizes, tolerances, material and performance specifications must be clearly indicated on an approved drawing or specification.
Inspection activities should be defined by product type, project specification and agreed inspection plan.
1. Material Inspection
Review Material certificate
Verify steel grade and heat number
Confirm chemical composition if required
Inspect incoming material dimensions
Inspect surface defects
2. Dimensional and Thread Inspection
Measure diameter and overall-length
Inspect thread profile and pitch
Verify threaded-length
Inspect straightness if required
Measure plate thickness and hole-size
Inspect mesh aperture and panel-dimensions
Coupler and nut fit checks
3. Mechanical and Proof Loading
Where specified by contract:
Inspect yield strength
Inspect ultimate tensile strength
Inspect elongation
Load test component, nut or coupler
Plate load/deformation testing
Mesh weld shear testing or weld strength testing
Perform project specific sample or batch testing
4. Weld Inspection
Inspect weld-positioning
Check weld consistency
Perform weld shear testing if specified
Check for incomplete or damaged welds
Mesh-panel edge dimensional checks
5. Surface Preparation and Coating Inspection
Inspect surface preparation
Measure coating thickness if required
Perform coverage and appearance checks
Inspect coated thread-fit
Shield mating surfaces
Inspect for coating damage incurred during transport
6. Identification and Closeout Inspection
Heat or batch identification
Product marking
Prepare inspection record
Confirm quantity
Inspect package
Confirm drawing & purchase order
Review shipping documents
7. Test Certification
If ISO certified, third party tested or required to meet ASTM, EN, AS/ NZS or project specific standards state:
Certificate/report number
Issuing party
Product tested/certified
Specification followed
Date of test & period of validity
Facility of origin
Attach certified report or provide download link
Logo’s of standards should not be shown unless there is proof they apply to the product and supply quantity.
Correct installation is as important to product performance as manufacturing quality control.
Installation considerations that should be addressed by the project installation plan include:
The approved ground-control plan, product instructions and local regulations should define all installation procedures and verification methods.
Complete as much as you can:
1. What products are typically used in weak fractured ground?
Rock bolts, fully grouted threaded bars, bearing plates, welded wire mesh, steel straps, cable bolts and other support elements may be used in combination to form an engineered support system. The appropriate system will vary based on ground behaviour, excavation geometry and required support capacity.
2. How do rock bolts strengthen fractured rock?
Rock bolts installed across joints and fractures can help pin blocks together and provide a connecting competent material. Performance will depend on length, orientation, anchorage, installation quality and characteristics of the rock mass.
3. Why would steel mesh be used with bolts?
Mesh prevents small pieces of rock from falling into an excavation between bolts. It is typically installed using compatible bearing plates/washers or straps in accordance with an approved support design.
4. Which type of bolt should I use in bad ground?
There is no magic bolt type that works in all poor boreholes. Important factors to consider when selecting bolts for bad ground include whether the hole is oversized, caving, water-bearing or just won’t hold its profile. Ideally the selected bolt and anchorage should be confirmed by engineering analysis and field installation trials.
5. Can friction bolts be used in fractured ground?
They can be used if the rockmass and borehole provide sufficient resistance to installation and can develop the required bolt load. Sensitivity to borehole diameter means that friction bolts often need to undergo drilling trials and installation or load testing.
6. How do I determine bolt length and spacing?
Spacing and length depend on many factors including excavation dimensions, discontinuity orientation / spacing / persistence, thickness of weak zones, expected failure mode(s), anchorage quality and design loads. Guidance on these parameters should be sought from an experienced geotechnical/mining engineer.
7. What options are there for corrosion protection?
Options may include uncoated steel, hot dip galvanising, or another coating system specified to suit project requirements. Availability will depend on the manufacturing process used. Corrosion protection should be selected based on groundwater chemistry, damage during installation and required design life.
8. Can Wanfeng manufacture bolts to project drawings?
Yes. We can review project drawings to assess material availability, tooling requirements, tolerances, testing and production capability. Please ensure all relevant information is clearly identified on the drawing including dimensions, steel grade, mechanical properties, threads per inch, coating specifications, inspection criteria etc.
