We offer a variety of bored pile retaining walls when provision for temporary and permanent support for basement excavations is required.

We have the expertise and technology to ensure that ground movements are controlled and an economic solution is found.

The most common methods, secant and contiguous walls are discussed on this page. However further guidance and explanation of different techniques can be found in CIRIA guide C760, Guidance on embedded retaining wall design.

Secant walls

Secant piles are installed by overlapping reinforced male piles and female piles which are installed with a low strength gain concrete. They are adopted to restrict groundwater and fines inflow with retained heights of up to 8m common. Greater excavation depths may be achieved. However the geological and hydrological conditions need to be considered along with installation tolerances when determining the suitability of the application.

secant walls

Contiguous walls

Contrary to their name, contiguous piles are actually installed with a gap of 100-200mm per pile. This means that the wall is not water or fines tight. However where the conditions allow, such as in cohesive soils, it can be the most economic form of retaining wall.

The choice of construction technique, CFA or Rotary, is dependent upon soil type but can range from 300-1200mm diameter.

This can provide retained heights of up to 15m with propping and 10m in a cantilever situation.

Sheet Piled Wall

The sheet pile wall is an earth retention and excavation support technique that retains soil using sheets made of steel with interlocking edges.

The connection between piles is ensured by a clutching system which is designed as a watertight joint.
The sheet piles have various shapes and they are consecutively installed using a vibratory hammer or by pressing.
It can be used both as temporary or permanent wall and it has the advantage that no arisings are produced and can be installed relatively quickly.

If only used for temporary condition, the sheet piles can be afterwards extracted and re-used.
The wall formed is relatively flexible and limited in depth by the capacity of the equipments use, the stiffness of the soil layers and the potential declutching in course-grained soils.

King Post Wall

The King Post or Soldier Piles is the most common technique for earth support. This type of wall uses steel column embedded into predrilled and filled boreholes with our CFA Rigs, followed by the insertion of wooden planks or precast concrete panels between the steel columns, as the excavation progresses.

It has the advantage of flexibility in regards to the shape and can be installed around obstructions. The installation process is quick and vibration free.