Temporary ground anchors provide short-term support for excavations, retaining walls, slopes and other structures. They are often used on basement excavations, underground car parks, road and rail projects, staged retaining systems and short-term slope stabilisation works.
However, the right anchor system depends on factors such as design life, ground conditions, loading, corrosion exposure and the construction sequence.
In this guide, we explain what temporary ground anchors are, how they differ from permanent anchors, and where they’re used. Keep reading to discover whether they may be the right solution for your next construction project.
Key takeaways
- Temporary ground anchors help maintain stability during construction where excavations, slopes, or retaining systems require additional restraint.
- They are commonly used on projects where support is only needed for a limited stage of the build.
- Typical applications include basements, underground structures, transport cuttings, staged earthworks and temporary slope works.
- Anchor selection depends on site conditions, required load resistance, groundwater, construction sequencing and the period of use.
- Temporary systems differ from long-term anchor solutions in areas such as durability, detailing, corrosion protection, access and lifecycle requirements.
- At the end of their service period, temporary anchors are usually unloaded and handled in accordance with the system design and project approvals.
- Boundary crossings can introduce additional legal and approval requirements, particularly where anchors extend beneath adjoining land or public assets.
What is a temporary ground anchor?
A temporary ground anchor is a tensioned support installed into soil or rock to stabilise retaining walls, excavations and other structures during construction.
By transferring tensile loads into stable soil or rock, they help control movement and keep temporary works secure while the permanent structure is completed.
This type of anchor is intended for a defined construction period instead of ongoing structural support. Its exact design life, layout, capacity and protection requirements depend on the ground conditions, anticipated loads, construction sequence and engineering specification.
Key differences between temporary and permanent ground anchors
| Factor | Temporary ground anchors | Permanent ground anchors |
| Design life | Used for a defined construction period, often for months and commonly less than two years. | Designed to remain in service for the required life of the completed structure, which may extend for decades. |
| Design focus | Engineered around short-term loads, excavation sequencing and the stage when the finished structure can take over support. | Designed for sustained performance, with added attention to durability, long-term protection and future access requirements. |
| Corrosion resistance | Protection is matched to the short service period and site conditions. Grout may provide adequate protection in suitable non-aggressive environments. | Requires corrosion protection suited to long-term underground exposure, which may include sheathing, ducts, grout, protective compounds and sealed anchor-head details. |
| Cost | Often more economical where the shorter service life allows simpler detailing and protection measures. | Can involve higher upfront costs due to added durability requirements, corrosion protection and provisions for long-term performance. |
Choosing the right ground anchor system is critical to structural performance, construction efficiency and project cost.
An anchor that’s under-specified may not meet the required performance or durability demands, while an over-specified system can add unnecessary complexity and expense.
Let’s take a closer look at the core differences between temporary and permanent ground anchors.
Design life
The main difference between temporary and permanent ground anchors is how long they need to perform. That design life affects corrosion protection, detailing, monitoring, access requirements and, in many cases, project cost.
Temporary ground anchors are generally designed to provide support during a defined construction period, often measured in months and commonly less than two years.
In contrast, permanent ground anchors remain in service for the specified design life of the completed structure, which may extend for many decades.
Design considerations
Both temporary and permanent ground anchors require geotechnical assessment, engineering design and controlled installation.
However, permanent anchors generally involve additional durability detailing to account for long-term corrosion protection, future access and continued performance.
Meanwhile, temporary anchor design focuses on the excavation sequence, short-term loading conditions and the point at which the completed structure can take over the load.
Corrosion resistance
Corrosion protection is a key difference between temporary and permanent ground anchors because steel tendons remain exposed to underground conditions for very different periods.
For suitable temporary anchors with a design life of up to two years, cementitious grout may provide sufficient tendon protection in a non-aggressive environment.
More aggressive soil or groundwater conditions can require additional measures even for short-term works.
On the other hand, permanent systems need corrosion protection designed to remain effective throughout their specified service life.
Depending on the anchor design, this can include protective sheaths and ducts, grout, corrosion-inhibiting compounds and sealed protection around the anchor head.
Costs
Temporary ground anchors often cost less where their shorter design life allows simpler corrosion protection and detailing. They can provide an efficient way to support excavations and retaining systems until the permanent structure takes over.
Permanent anchors can carry higher upfront costs because their design may require more extensive corrosion protection, durability measures, monitoring provisions and accessible anchor-head details.
Ultimately, anchor length, capacity, drilling conditions, ground type and site access affect the final cost of either system.
Temporary ground anchor applications
Basement and deep excavation support
Temporary anchors are widely used to restrain shoring and retaining walls during basement, underground car park and deep excavation works.
Anchors can be installed progressively as excavation advances, helping the retaining system resist lateral ground pressures while keeping the excavation area relatively clear for construction.
Temporary retaining systems
Ground anchors can provide additional restraint to temporary retaining walls, including piled and other engineered shoring systems.
This is particularly useful where site constraints make internal bracing difficult or where the retaining wall must remain stable throughout staged excavation.
Road and rail cuttings
During road and rail construction, temporary ground anchors can support retaining structures and excavated cuttings while earthworks, structures or other stabilisation measures are completed.
Their layout and capacity are designed around the ground conditions, construction sequence and loads acting on the excavation.
Short-term slope stabilisation
Temporary anchors can help restrain unstable soil or rock where short-term support is required during slope remediation, infrastructure upgrades or staged earthworks. They may be used to control movement while longer-term works are constructed.
Construction staging
Some projects need temporary restraint only during a particular stage of construction. Ground anchors can support retaining walls or structural elements until slabs, bracing, foundations or other completed works can provide the required stability.
Temporary uplift restraint
Ground anchors can also provide temporary hold-down resistance where uplift forces act on a structure during construction.
This may include situations involving groundwater pressure or temporary structural loads before the completed structure has sufficient capacity or weight to resist uplift on its own.
Installing and removing temporary ground anchors
Temporary anchors are typically installed every three meters. During installation, a borehole is drilled through or behind the retaining system at a location and angle set by the engineering design.
A high-strength steel strand or bar tendon is then installed and grouted into the ground before being stressed to apply the required restraining force.
As excavation progresses, anchors may be installed in stages or rows to control movement and maintain stability until the building or other structural works can support the retained ground without temporary assistance.
Once the permanent structure can safely support the retained ground, the anchors are typically de-stressed. This releases the load from the tendon, allowing the exposed anchor head and associated components to be removed or cut back as required.
Note that the entire anchor doesn’t necessarily come out of the ground. With conventional grouted strand anchors, some below-ground components may remain in place.
Where full removal is required, purpose-designed removable anchor systems can allow the tendon or other components to be extracted after use.
FAQs
How long can temporary ground anchors be left in place?
Temporary ground anchors are generally designed for short-term construction support, with a design life usually less than two years.
The required lifespan depends on the project, ground conditions, exposure environment and corrosion protection specified by the engineer.
If support is needed for longer, the anchor may require additional durability measures or a design that meets permanent anchor requirements.
Can temporary ground anchors be reused?
Can a temporary anchor be converted to a permanent one?
Is a permit required for temporary ground anchor installation?
Explore temporary ground anchoring services
Temporary ground anchors help stabilise excavations, retaining structures, slopes and other temporary works during construction. Their configuration should be selected to suit the site geology, applied forces, installation sequence and required service period.
The RIX Group delivers ground anchor systems for complex site conditions and project requirements across Australia and the Asia Pacific.
With experienced crews, specialist drilling equipment and strict quality control, we provide practical solutions from initial design through to installation and testing.
Contact us to discuss ground anchoring services for your next project.