Deep excavations alter lateral stresses in the ground and local patterns of groundwater flow. They also create construction-stage conditions that can change as each stage of excavation progresses. Some of these conditions and risks include:
Note that the critical condition may occur at an intermediate stage of construction, not necessarily at the maximum excavation depth.
A complete deep excavation support system may include several interacting elements.
| System element | Typical function |
| Retaining wall | Retains ground and controls deformation |
| Ground anchors | Provide external prestressed restraint |
| Internal struts | Restrain the wall from inside the excavation |
| Soil nails | Reinforce suitable in-situ ground during staged excavation |
| Rock bolts or dowels | Reinforce joints and blocks in rock |
| Walers | Distribute anchor or strut loads along the wall |
| Facing | Retains material between reinforcement points |
| Wall embedment | Provides passive resistance and base stability |
| Groundwater cutoff | Limits seepage and ground loss |
| Dewatering | Reduces water levels or pressure |
| Ground improvement | Strengthens weak ground or reduces permeability |
| Underpinning | Protects nearby foundations |
| Monitoring | Measures wall, ground, water and support response |
A steel bar, plate or mesh panel cannot independently provide complete excavation support.
Wanfeng provides reinforcement and connection elements that could be included in professionally engineered anchored, nailed, braced or rock-supported excavations.
Soil nail bars with threads can be used to reinforce soil that is capable of being temporarily exposed in stages. Ground-anchor bars can be used to transfer wall loads through a predetermined bond zone outside of the potential failure mass. Rock bolts or dowels can be used to reinforce rock masses. Plates, nuts, couplers and centralizers are used to connect these bars and ensure they are positioned within the specified system.
Wanfeng components can be used with (when properly designed):
Intended Component Functions
When properly designed, the provided components can be used to:
Engineering Disclaimer
Final wall type, embedment, excavation sequencing, level of support, anchor/nail length, bond zone length, prestress, strut loadings, groundwater control and monitoring plans should be engineered or checked by professional civil/structural and geotechnical engineers.
Factors the engineering should consider include:
Wanfeng provides components in accordance with confirmed specifications, but will not specify a safe unsupported depth of excavation or serve as a substitute for the projects temporary-works engineer.
| Support system | Typical application | Principal advantages | Important limitations |
| Sloping or benching | Sites with sufficient space and suitable ground | Simple geometry with fewer structural components | Usually impractical in restricted urban sites |
| Soil nail wall | Ground capable of staged temporary exposure | Top-down construction and adaptable facing | Requires face stability and external installation space |
| Ground-anchored wall | Deep excavation with suitable external bond zone | Keeps the excavation interior relatively open | Requires easements and specialist testing |
| Internally braced wall | Restricted boundaries or anchor conflicts | Does not require anchors outside the site | Struts and walers restrict excavation operations |
| Cantilever wall | Moderate excavation with sufficient wall stiffness | No internal or external supports | Wall deflection and embedment often govern |
| Top-down construction | Urban excavation integrated with permanent floors | Permanent slabs provide staged restraint | Complex structural sequencing and connections |
| Rock-bolted excavation | Competent or fractured rock | Targets discontinuities and unstable blocks | Does not automatically support overlying soil |
| Underpinned excavation | Excavation beside sensitive foundations | Protects or transfers adjacent structural loads | Requires close structural and geotechnical coordination |
System suitability must be determined from site-specific design.
1.Threaded Soil Nail Bars
Used as steel reinforcement for soil nail walls and may be appropriate for staged excavation support.
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Other Fields
2.Threaded Ground-Anchor Bars
May be used as high strength threaded bars that comprise the tendon of a prestressed ground anchor system.
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Other Fields
Application Notes
A ground anchor may also require grout, sheathing and encapsulation material, anchor head, bearing plate, trumpet, lock-off components and field load testing before considered complete.
3. Coupled Reinforcement Bars
Sectional threaded bars connected with compatible couplers. Used where overall length prohibits shipping or where site access does not allow installation as a single piece.
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4. Rock Bolts and Dowels
Steel reinforcement bars used to support rock sections exposed during deep excavations.
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Application Notes
Rock-bolt orientation and length should consider geological mapping carried out across site and any discontinuities identified or potential failure surface.
5. Bearing and Anchor Plates
Steel plates utilized to transfer load from bars, nail heads, anchor heads to approved structural connections.
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Application Notes
Soil nail plates, rock-bolt plates and ground-anchor bearing plates will have different load capabilities and stiffness requirements. Assess each plate on its individual merit rather than assuming all plates can substitute for each other.
6. Nuts and Washers
Compatible threaded components used on nail heads, anchor bars and other approved connections.
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7. Centralizers and Spacers
Parts used to centralize bars within drilled holes and provide minimum required grout cover.
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Other Fields
8. Welded Wire Mesh
Steel mesh that may be used to reinforce the initial shotcrete facing or retain small loose material.
Other Fields
Application Notes
Mesh sizing does not quantify the capacity of the complete shotcrete facing. Shotcrete thickness, strength of concrete, reinforcement details, nail-head connections and construction joints all need engineering input.
9. Strut, Waler and Connection Components
Fabricated components used for internal bracing or connections to walls may include:
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Availability note
Do not list fabricated bracing components until manufacturing, welding procedures, nondestructive testing and dimensional control capabilities are confirmed.
10. Hollow or Self-Drilling Bars
Bars with a hollow center that can be threaded may be used when conventional boreholes cannot be maintained.
Other Fields
Availability
Do not list self-drilling bars until the bars, couplers, drill bits and technical data sheets are confirmed compatible.
| Typical site condition | Typical support requirement | Systems or products that may be relevant |
| Stiff soil with temporary face stability | Top-down ground reinforcement | Soil nails, drainage and reinforced facing |
| Deep urban excavation | Stiff wall and staged lateral support | Pile or diaphragm wall with anchors, struts or slabs |
| Restricted property boundary | Support contained within the site | Internal struts, rakers or top-down slabs |
| Suitable external anchor zone | Open working area inside excavation | Ground-anchored retaining wall |
| Sensitive neighboring structure | Low deformation and continuous monitoring | Stiff wall, closely staged support and possible underpinning |
| Loose granular soil | Ground-loss and borehole control | Pile wall, casing, ground improvement or specialist installation |
| Soft clay | Wall movement and basal-heave control | Embedded wall, bracing and possible base improvement |
| Water-bearing sand | Seepage, piping and ground-loss control | Cutoff wall, dewatering, recharge or ground improvement |
| Mixed soil and rock | Support adapted to changing strata | Hybrid wall, nail, anchor and rock-bolt system |
| Competent rock with localized blocks | Discontinuity reinforcement | Rock bolts or dowels with surface retention |
| Weak ground below excavation base | Base stability and uplift control | Ground improvement, deep wall embedment or other engineered measures |
| High surcharge near the excavation | Increased wall and support loads | Project-specific wall, anchor or bracing design |
| Temporary excavation | Construction-stage support | Components suitable for actual duration and exposure |
| Permanent basement wall | Long-term structural integration | Permanent wall and verified corrosion protection |
| Seismic condition | Temporary and permanent seismic response | Project-specific geotechnical and structural analysis |
No option is universally preferable. Selection depends on ground, geometry, property access, movement tolerance and construction sequence.
Components Wanfeng May Supply
Dependent on confirmed production capacity:
Systems That May Be Needed
Do not list as supplied by Wanfeng until capable:
Soil Nail Wall
A Typical sequence may include:
Ground-Anchored Wall
A Typical sequence may include:
Internally Braced Excavation
A Typical sequence may include:
The above sequences are examples only. Excavation lifts, length of unsupported periods, support levels, test loads, and removal sequences must be in accordance with approved project documentation.
Groundwater can control whether a deep excavation can be constructed.
Elements to be considered in the project water-control plan may include:
Options may include:
Ground-water systems must be engineered separately and should not be assumed to be included with the purchase of steel.
Factors to consider when supporting deep excavations include:
Controls that may be considered:
Wanfeng Engineering Group will not set movement thresholds or monitoring trigger levels as acceptable or not acceptable.
Wanfeng will evaluate approved product schedules and connection drawings for manufacturability.
Items to consider for customization are:
Verify all dimensions, tolerances, loads, material and coatings with approved drawings or technical specifications prior to manufacturing.
Raw Material Inspection
Bar, Bolt and Thread Inspection
Mechanical and Connection Testing
Where applicable and contractually specified:
Dimensional Inspection
Surface Treatment Control
Identification and Final Inspection
| Test or inspection | Typical location | Purpose |
| Bar tensile test | Factory or laboratory | Verify material properties |
| Coupler tensile test | Factory or laboratory | Verify connection capacity |
| Nut proof-load test | Factory or laboratory | Verify threaded connection performance |
| Plate inspection | Factory | Verify material and dimensions |
| Mesh weld test | Factory or laboratory | Verify specified weld strength |
| Coating inspection | Factory | Verify corrosion-protection requirements |
| Soil nail verification test | Project site | Assess installation method and ground bond |
| Soil nail proof test | Project site | Check production-nail performance |
| Ground-anchor verification test | Project site | Assess bond-zone resistance |
| Ground-anchor performance test | Project site | Assess installed load–movement behavior |
| Ground-anchor proof test | Project site | Verify production-anchor performance |
| Strut preload verification | Project site | Confirm initial bracing condition |
| Wall and settlement monitoring | Project site | Assess excavation response |
Factory steel strength does not verify installed ground resistance or overall excavation stability.
Monitoring could involve:
Warning signs could include:
Engineers of record should establish monitoring frequency and warning levels/steps prior to excavation.
1. What is meant by deep excavation support?
Deep excavation support is a structural system designed to retain earth or rock mass, control groundwater and minimize movement whilst excavation takes place. This could consist of retaining walls, anchors, soil nails, struts, drainage systems, ground improvement techniques and instrumentation for monitoring.
2. What types of systems are used to support deep excavations?
Typical systems include soil nail walls, ground anchored walls, internally braced pile walls, diaphragm walls, sheet piles, top- down construction and rock- bolted excavations. The best choice of system will depend on many site specific factors.
3. What is the difference between soil nails and ground anchors?
Soil nails are typically passive and are often fully grouted into place. Ground anchors are usually prestressed and have distinct free and bond lengths prior to being locked off against the supporting wall.
4. Why would internal struts be used instead of ground anchors?
Internal struts could be chosen if anchors were unable to extend beyond the site boundary, if utilities restricted the anchor zone or if external ground is not capable of developing enough bond resistance.
5. Can rock bolts be used to support a soil and rock excavation?
Rock bolts can be used to reinforce the rock cut, however the soil above may still require a retaining wall, soil nails, facing or other type of support system. Designs for soil and rock often incorporate elements of both and are referred to as hybrid designs.
6. Why is groundwater control necessary?
Groundwater pressure can result in piping, uplift pressures, ground loss and base instability. Lowering groundwater levels can also result in settlement beyond the excavation, therefore careful design of groundwater control and monitoring is required.
7. Does Wanfeng provide complete excavation- shoring systems?
Confirmed steel bars, bolts, plates, couplers, nuts, mesh and drawing based connection components can be evaluated by Wanfeng. However, complete walls, bracing systems, dewatering and monitoring may require additional suppliers.
8. Does Wanfeng manufacture based on project drawings?
Yes. Provided component drawings are approved by your engineer, Wanfeng can confirm materials, sizes/dimensions, threads, loads, coating requirements, testing and production capability. Overall design decisions are not within our scope.
