Bored Pile Retaining Walls - Contiguous & Secant

Continuous Flight Auger Bored Piles

MEC Piling use two methods of bored piling techniques for contiguous piled walls, CFA and rotary. Where the available working area dictates that basement excavation faces must be vertical, these two techniques provide special advantages. Both methods are technically effective and are a cost effective method of providing temporary or permanent means of retaining the sides of bulk excavations, even in water bearing strata.

Contiguous piled walls can be designed to accommodate vertical loads in addition to horizontal forces when they are used in permanent works and the construction techniques for both methods are the same as for foundation bearing piles.

Secant Piled Retaining Walls 

MEC Piling can offer Secant piled retaining walls, which are suitable for basements and underground structures where working space is limited or adjacent to existing structures.

Secant piled retaining walls are formed using either Rotary or CFA piling technics, unreinforced female piles are installed at close centres using a slow-gain (soft) concrete mix, after a sufficient curing period and once each alternate pile has been installed, the reinforced male piles are installed using a standard concrete mix.

The overlap for a typical secant section is approximately 75 – 100mm which ensures that water ingress is minimised and fines wash-out is prevented. The interlocking secant wall is not watertight; however water flow is greatly reduced.

These piles form temporary or permanent support to excavations.