Factors that affect the performance of an anchored wall include the wall itself, the anchor tendon, the bond to the ground, structural connections between the elements, installation sequence, and groundwater conditions. Typical design challenges include:
The installed capacity of a ground anchor is NOT solely determined by the tensile strength of the steel tendon.
A retaining-wall ground anchor generally includes more than a steel bar or strand.
| Anchor component | Typical function |
| Tendon | Carries tensile load |
| Bond length | Transfers load through grout to the surrounding ground |
| Free length | Allows tendon elongation during stressing |
| Primary grout | Transfers load and provides part of the protection system |
| Sheathing or encapsulation | Separates and protects specified tendon zones |
| Centralizers and spacers | Maintain tendon position and grout cover |
| Anchor head | Transfers tendon force to the wall or waler |
| Bearing plate | Distributes force at the structural connection |
| Nut or wedge assembly | Secures and locks off the tendon |
| Trumpet or transition protection | Protects the tendon near the anchor head |
| Secondary grout or head protection | Completes project-specified protection |
| Waler or structural connection | Distributes anchor loads into the retaining wall |
Only describe a product as a “complete ground-anchor system” when all required components, interfaces and testing documentation have been verified.
Wanfeng provides threaded steel tendons and anchoring hardware that can be used in a ground-anchor retaining wall system.
The threaded bar is designed to resist the required tensile load. The bonded length develops that load into good soil/rock behind the failure plane. The free length allows for movement when testing and stressing the tendon. The anchor head, bearing plate and waler distribute the locked-off load into the retaining wall structure.
Depending on the design, this system can integrate with many different types of walls including:
Functions of the System
A ground-anchor wall system can be designed to:
Engineering Disclaimer
Final determination of wall type, anchor angle, spacing, overall length, free length, bond length, test load, lock-off load, grout, corrosion protection and structural connection should be designed by or reviewed by professional geotechnical and structural engineers. The engineering design should include, but not be limited to:
Wanfeng only supplies parts to meet specified drawings and does not set site specific anchor capacities, allowable lock-off load values or safe excavation criteria.
These terms should not be used interchangeably.
| Characteristic | Prestressed ground anchor | Soil nail | Tie rod |
| Typical behavior | Active, prestressed reinforcement | Generally passive reinforcement | Structural tension member between defined connections |
| Load application | Tested, stressed and locked off | Resistance develops with ground deformation | Loaded through structural movement or assembly |
| Grouting | Defined free and bond lengths | Commonly grouted along the installed length | May not be ground-grouted |
| Typical wall connection | Anchor head and waler or structural wall | Nail head and reinforced facing | Nuts, pins, clevises or structural plates |
| Typical spacing | Project-specific, often wider than soil nails | Usually closely spaced | Determined by structural system |
| Field testing | Verification, performance, proof and creep tests as specified | Verification and proof tests as specified | Structural testing where required |
| Primary design discipline | Geotechnical and structural | Geotechnical and structural | Primarily structural, depending on application |
Project drawings should clearly identify the intended component behavior.
Threaded Ground-Anchor Bars
High strength threaded steel bars that can be used as the tendon of a project designed ground anchor.
Specifications
Optional
Coupled Anchor Bars
Sectional bars which are connected using compatible couplers where long anchor lengths, transport limits or installation access prevent the use of one-piece ground anchor tendons.
Specifications
Optional
Notes: Coupler strength and placement must be designed as part of the complete tendon assembly. The placement of a coupler should not occur automatically within a critical length without approval from the engineering team.
Anchor Bearing Plates
Steel plates which are used to transfer the force from a tendon into an approved anchor head, concrete waler or retaining-wall connection.
Specifications
Optional
Notes: Anchor plate size and thickness must be evaluated for bending/stresses and bearing pressure. Just because a plate fits in a wall anchor or onto a waler doesn’t mean it is adequate based on capacity or attachment details. A standard rock-bolt plate is not necessarily appropriate for use as a retaining wall anchor plate.
Anchor Nuts and Washers
Components that are thread-compatible with anchor bars to stress, secure, or lock-off installed anchors.
Specifications
Optional
Centralizers and Spacers
Steel components used to maintain tendon position within the borehole and provide the minimum required grout cover.
Specifications
Optional
Strand Tendons and Wedge Anchorages
Multi-strand prestressing strand may be specified if project loads, stressing lengths, or installation requirements dictate the use of a stranded tendon.
Specifications
Optional
Notes: Strand tendons, wedge assemblies, and multi-strand anchor heads should not be listed until Wanfeng’s manufacturing capability, system testing, and reference testing have been completed and verified.
Rock Anchors
Bars or cable reinforcement that can be tensioned to retain structures against competent rock.
Specifications
Optional
Notes: Rock anchorage does not negate the need to identify joints, assess fractures or faults, identify weakness due to weathering, or identify likely location of potential failure surface(s).
Waler and Connection Components
Custom connection components fabricated from steel to help distribute anchor forces into concrete retaining walls.
Possibilities
Specifications
Notes: Fabricated wall anchor connections should not be proposed until approved connection drawings have been reviewed and manufacturing as well as welding/inspection capability is confirmed. Upload Connection Drawings
| Typical wall or site condition | Typical requirement | System or products that may be relevant |
| Soldier-pile wall with available external anchor zone | Staged lateral restraint | Prestressed ground anchors with walers |
| Secant or diaphragm wall | High-capacity wall connection | Bar or strand anchors with engineered head details |
| Sheet-pile wall | Distributed tieback support | Anchors connected through walers or approved structural details |
| Existing concrete retaining wall | Control of movement or increased loading | Retrofit anchors only after wall and foundation assessment |
| Retaining wall founded against rock | Anchorage into suitable rock mass | Threaded rock anchors or strand tendons where designed |
| Deep excavation with open internal workspace | External support without internal struts | Ground-anchored wall where property rights allow |
| Anchor zone outside project boundary | Legal and access constraint | Easement, revised anchor layout or internal bracing |
| Loose water-bearing soil | Borehole and grout control | Specialist drilling, casing and grouting system |
| Cohesive soil with creep potential | Time-dependent movement control | Project-specific testing and creep acceptance criteria |
| Aggressive soil or groundwater | Long-term corrosion resistance | Verified multi-layer or encapsulated protection |
| Temporary retaining wall | Defined construction-stage support | Anchor components suited to the actual exposure period |
| Permanent retaining wall | Long-term strength and durability | Permanent anchor system with documented corrosion protection |
| High seismic or surcharge loading | Increased structural and geotechnical demand | Project-specific anchor and wall analysis |
| Inadequate external bond zone | Alternative load path | Internal struts, rakers or redesigned retaining system |
Selection Note：
| Design consideration | Temporary anchor | Permanent anchor |
| Service period | Defined construction duration | Full structure design life |
| Corrosion protection | Based on actual exposure and specification | Long-term verified protection system |
| Free-length protection | Project-specific | Durable and continuous protection |
| Bond-length protection | Grout and additional protection as specified | Designed for long-term ground exposure |
| Anchor-head protection | Temporary or removable protection | Durable, sealed and inspectable detail |
| Testing | Project-specified verification and production testing | Complete testing and permanent records |
| Monitoring | Construction-stage requirements | Long-term monitoring where specified |
| Replacement | May be abandoned or destressed under an approved plan | Replacement may be difficult or impractical |
A construction delay may extend the actual exposure of a temporary anchor. Temporary status should not be used to justify unspecified materials or uncontrolled corrosion risk.
Ground-anchors are vulnerable to corrosion as they are members under sustained tensile stress.
Corrosion protection may need to consider:
Protection methods can consist of:
Important Limitation
Note that coating the bar alone does not define a complete permanent-anchor corrosion protection system.
Avoid using statements such as “double corrosion protection” unless:
Replacement of a more protective system with a less protective system should be subjected to engineering approval.
The following is an example of a typical bar or strand anchor sequence:
Actual construction procedures shall comply with the project specifications, installation Method Statement and acceptance criteria.
Ground anchors must be tested on site to verify installed performance as it is dependent on the ground, drilling and grouting conditions.
Verification Test
Verification testing is typically conducted prior to or during production work to evaluate:
Performance Test
Performance testing is typically conducted with incremental loading and unloading to evaluate:
Suitability of the production installation method
Proof Test
Proof testing is typically conducted by loading a production anchor with a project defined loading cycle to evaluate:
Lock-Off
Successful proof tests will then be stressed to the project specified lock- off load and secured.
Wanfeng will not define field test loads, acceptance limits, test frequency or lock-off loads.
Raw Materials Verification Inspection
Tendon and Thread Verification Inspection
Mechanical and Connection Tests
As required and specified in the contract documents:
Dimensional Inspection
Surface Preparation and Coating Inspection
Identification and Final Inspection
| Test or inspection | Typical location | Purpose |
| Bar tensile test | Factory or laboratory | Verify tendon material properties |
| Strand breaking-load test | Factory or laboratory | Verify strand capacity |
| Coupler tensile test | Factory or laboratory | Verify connection capacity |
| Nut proof-load test | Factory or laboratory | Verify threaded nut performance |
| Bearing-plate inspection | Factory | Verify material and dimensions |
| Coating inspection | Factory | Verify specified protection |
| Anchor verification test | Site | Assess bond resistance and installation method |
| Performance test | Site | Assess installed anchor behavior |
| Proof test | Site | Verify production-anchor performance |
| Creep test | Site | Assess time-dependent movement |
| Wall monitoring | Site | Assess retaining-wall movement |
Factory tendon strength must not be presented as proof of installed ground-anchor capacity.
All sizes, loads, material, tolerances, and protection requirements must be confirmed on approved drawings or technical specifications prior to production.
Items that may be included in the project inspection and monitoring plan are:
Warning Indicators
Anchors that fail or are not compliant should be assessed through the project’s approved corrective-action plan.
Q1: What is an anchored retaining wall?
A: Anchored retaining walls utilize prestressed ground anchors to convey lateral wall loads into a competent soil or rock mass (bond zone) located behind the retaining wall. Anchors installed are designed to function with the wall, walers, drainage and foundations as a system.
Q2: What is the difference between a ground anchor and a soil nail?
A: Generally, ground anchors are actively prestressed, have defined free lengths and bond lengths, and are locked off against the wall. Soil nails are typically passive and are fully grouted, developing resistance as the ground deforms.
Q3: Can a threaded bar by itself be considered a complete ground anchor?
A: No. Additional considerations could include a bond zone, free-length protection, grout, couplers, centralizers, anchor head, bearing plate, trumpet, lock-off component(s), and corrosion protection.
Q4: How do you verify ground- anchor capacity?
A: Installed anchors are tested on site to confirm design through verification testing, performance testing, proof testing or creep testing as required. Ground bond and installed behavior can be assessed through these tests, which cannot be determined from factory testing of steel.
Q5: What is meant by anchor lock- off load?
A: This refers to the load at which a properly accepted anchor is locked off against the retaining structure after stressing has occurred. The engineer of the project must specify this value.
Q6: Can ground anchors go across a property line?
A: No, unless the legal right to do so is acquired through easements and permits. If required to stay within your property line for external anchors, then an internal bracing system or alternative retaining system will need to be designed.
Q7: What types of corrosion protection are available?
A: Corrosion protection can consist of grout, galvanizing, epoxy coatings, sheathing, encapsulation, corrosion inhibiting compounds and protected anchor heads. Many permanent systems utilize multiple types of corrosion protection.
Q8: Can Wanfeng manufacture from anchor drawings?
A: Yes, Wanfeng has the ability to review threaded bars, couplers, nuts, plates, centralizers and fabricated connection drawings to determine if the part(s) can be manufactured. However, the entire anchor and wall design is the responsibility of the engineer of record.
