Contiguous Pile Walls

Contiguous pile walls are used as part of a shoring system, for the purposes of earth retention, and provide an efficient and cost-effective solution for the construction of retaining walls. As a bonus, these temporary or permanent structures benefit the environment by providing an earth-retaining solution that restricts soil movement on the retained side of wall while requiring minimal excavation.

Contiguous Pile Walls

What Are Contiguous Pile Walls Used For?

This type of piling is ideal for use in built-up urban areas or industrial settings, because of its low levels of vibration and noise generation and its minimal deformation of the adjacent ground or soil mass. These non-displacement piles are an economical solution for supporting significant vertical and horizontal structural loads.
Contiguous pile walls are generally suited to the following fields of use:

This method of earth retention and shoring is the perfect choice for supporting an excavation on a site where underground utilities and the footings of adjacent buildings are present, and traditional earth-retention methods would encroach upon those adjoining sites.

Contiguous Pile Walls » contiguous pile walls
Contiguous Pile Walls » contiguous pile walls
Contiguous Pile Walls

Ground Suitability

Rotary drilling techniques mean this form of earth-retention system suitable for wide variety of ground conditions, from soft layers of rock, to granular soils and gravel, most cohesive soils, and grounds with a mixture of strata. Bored piles are also generally suitable for use in hard to extremely hard rock or hard clay ground conditions, while CFA piles are suited to ground that is unstable or highly saturated.
Contiguous Pile Walls » contiguous pile walls
Contiguous Pile Walls » contiguous pile walls
Where ground is considered unstable, segmental, or temporary casing and permanent steel liners, polymers or bentonite slurry may be used for bored piling. Contiguous pile walls with gaps that have not been sealed by jet grouting, ‘shotcreting’ or ‘gunite’ are not suited to:
Contiguous Pile Walls​

How Are Contiguous Pile Walls Constructed?

Contiguous pile walls are constructed by drilling successive, adjacent piles, leaving only small gaps between piles. Both the optimal diameter and spacing of the piles are governed by the soil type and the level of ground water, however the nominal gap is usually between 100mm to 150mm. Large spaces between piles are generally avoided as they are more likely to result in ground materials from the retained side of the wall being lost through the gaps.

The piles are intended to bear tension loads and lateral bending forces, and the addition of a capping beam at the top of the piles helps to distribute downward pressure equally across the piles and ensures they act uniformly. This kind of retaining wall can also support an axial load (line load and/or point load), distributed through the capping beam.
Contiguous pile walls are formed by using rotary bored piles or Continuous Flight Auger (CFA) piles to construct a row of unconnected, cast in-situ concrete piles. The decision on whether to use bored piles or CFA piles is usually determined by the purpose for which the wall is being constructed.

Contiguous Pile Walls​

Rotary Bored Piles

Bored piles are constructed using a modern drill rig to bore a hole of the required diameter. Bored piles offer the largest pile diameter up to 4 metres – and to a depth of 90m. The process involves repeatedly drilling, then withdrawing the drill to remove ground material from the pile, until the required depth is reached. After the pile base is cleared of excavated material, reinforcement steel is placed in situ and concrete is poured.

Contiguous Pile Walls » contiguous pile walls
Contiguous Pile Walls » contiguous pile walls
Contiguous Pile Walls​

CFA Piles

CFA piles, otherwise known as grout injected piles, are constructed by using a continuous auger to bore a hole of the required diameter –up to 1.2 metres and to a depth of up to 36m while injecting a special concrete mix or a sand-cement grout down the auger’s hollow stem while the auger is being extracted. This method avoids the need for temporary casings and is ideal for the construction of contiguous pile walls in soils that are not cohesive or have a high-water content.

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