This method is commonly used for stabilising basement excavations or existing unstable slopes, providing an in-situ reinforced earth solution.

Soil nails—either conventional types installed into pre-drilled holes or Self-Drilled Anchors (SDAs) that combine drilling and installation in a single step—are installed in a close grid pattern, allowing the soil mass to act as a single, reinforced unit. The nail grid is then secured with a layer of reinforced shotcrete, creating a continuous support system

This technique can be applied as either a temporary or permanent solution and is highly economical under the right conditions.

Advantages:

• Cost-effective for slope stabilisation and basement support

• Flexible for various excavation shapes, including multiple benches

• Uses compact, lightweight equipment ideal for restricted access sites

Limitations:

• Not suitable where large surcharge loads are close to the excavation

• Not recommended for excavations below the water table

Tensioned anchors are widely used for lateral support in deep excavations subject to high surcharge loads, and are often integrated into piled retaining wall systems. They can also be applied to tie back large structures spanning deep-seated failures or to resist uplift forces.

Anchors can be installed as either temporary or permanent systems, with permanent designs offering a lifespan of up to 120 years.

Advantages:

• Suitable for most ground conditions with proper pressure grouting

• Effectively limits ground movement and accommodates high surcharge loads

• Ideal for stabilising deep-seated failures

• Permanent systems can be designed for up to 120 years of service life

Limitations:

• Long-term anchors require ongoing monitoring and maintenance throughout their service life

Concrete soldier piles are a versatile component in lateral support systems. They can form cantilever retaining walls, be tied back with anchors, or braced depending on the design. In many cases, soldier piles also carry vertical loads and are integrated into the permanent structure of a building.

Installation and Pile Types

Soldier piles are typically installed at 0.5m to 1.5m centres before basement excavation begins. The following pile types are commonly used:

• Driven Displacement Cast-In-Situ (DCIS) piles

• DTH (Down-the-Hole) piles

• Continuous Flight Auger (CFA) piles

• Forum Bored piles

• Auger piles

Advantages

• Can support both lateral and vertical loads

• Easily incorporated into permanent structural works

• Effective for deep-seated failure support

• No corrosion protection required

• Highly adaptable for a wide range of site conditions

Limitations

• May encroach into the footprint of permanent works

This system is typically used as a temporary lateral support solution in sandy soils below the water table. It is commonly applied for trenches or pit excavations and allows for safe, effective support to depths of up to 8 metres in sand.

Installation and Method

The process begins with driving soldier piles—typically H- or I-section steel beams or fabricated steel members—around the perimeter of the proposed pit using a piling rig. A horizontal steel whaler is then welded inside the perimeter, connecting the piles. Excavation begins, and 6 m × 3 m timber panels are placed between the soldier piles and pushed downward as soil is removed.

Additional whalers are installed at 2.5 m to 3 m intervals as excavation progresses. This process is repeated until the final depth is reached.

Advantages

• Fast to install with basic equipment

• Ideal for sandy conditions

• Allows partial reuse of materials

Limitations

• Requires dewatering in areas with high water tables

• May cause settlement during construction, making it unsuitable near sensitive surrounding infrastructure