Retaining walls

Retaining walls

We design and install diaphragm, secant, contiguous and sheet steel walls to extremely tight tolerances.

We can combine a variety of piling techniques for excavation support projects encompassing bored pile retaining walls, diaphragm walls and sheet pile walls.

Bored retaining walls

Used most frequently for building basements, we can combine this technique with the installation of plunge piles to enable top down construction and thereby reduce the programme.

Either open bored or continuous flight auger techniques can be used to create retaining structures to cater for all ground and water conditions. There are three broad types of wall. Essentially primary piles are installed at suitable spacing to allow secondary piles to be installed between.

Secant pile wall (hard/hard)
Secant walls have a positive interlock between adjacent concrete piles, and so are particularly suitable where high water retention is a consideration Both primary and secondary piles can be reinforced enabling high lateral loads to be supported.

Secant pile wall (hard/soft)
This wall is used where considerations of retained height and water retention are less critical. Primary piles use self hardening slurry as a water and fines retaining membrane.

Contiguous pile walls
Used in locations where water retention is not a consideration and soils are cohesive, contiguous bored walls dispense with intercut piles completely.

Diaphragm walls

Diaphragm walls are underground structural elements commonly used as retention systems and permanent foundation walls.

They can also be used as groundwater barriers. A reduced number of joints means that diaphragm walls have improved water tightness compared to secant walls. Diaphragm walls tend to be used for retaining deep excavations as they can be designed to take high structural loads.

Our experience in diaphragm walling is extensive with projects ranging in size from 2,000 to 50,000mand from a few metres to over 50 metres deep. We are experienced in carrying out complex operations on restricted urban sites and have installed diaphragm walls at Heathrow's Terminal 2B and in low headroom in the redevelopment of Westminster Station.

Kingpost walls

Largely used as temporary retaining walls, this system uses a kingpost (open bore filled with concrete to form a base for steel H-pile). Panels of timber sleepers, precast concrete or steel sheets can then be slotted into the H-piles to form the retaining wall.

Please click here if you are looking for information about Balfour Beatty's patented King Sheet PilingTM (KSP) retaining wall system.