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Pile wall
Construction sequence
Secant pile wall construction sequence [example shown using twin rotary-drive technique see cased auger pile]
1. Construction of the concrete guide beam before piling commences (excavated trench with polystyrene spacers, so-called pile locators replicating the expected profile of the finished wall and reinforced concrete beam at each side of the spacer, so-called double guide wall)
2. / 3. / 4. Installation of the piles in phases. Formation of ‘primary’ piles.
Subsequent formation of complementary ‘secondary’ piles by boring down at the midpoint between 2 adjacent primary piles.
The piles are formed under the protection of recoverable casing.
5. Placement of the reinforcement before or after concreting.
Only the secondary piles are reinforced.
6. Completed secant pile wall
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Fields of application
• Can be installed throughout certain types of obstacles and old basement foundations (i.e. underground masonry).
• Depending on the applied technique (see § ‘Technical specifications’), drilling can be done through rock layers or concrete.
• Adaptable to irregular geometry and layout of excavations, difficult contours (with respect to diaphragm walls, pile walls have an increased construction alignment flexibility)
• Excavations of limited size (small-scale, with reduced dimensions)
• Sinking or reception shaft for seepage works.
Environmental impact
• Vibration-free
• Removal of soil
• Low noise pollution
• A stable, dry and flat work platform is needed.
Technical specifications
• The pile walls can be constructed by using the following techniques:
tangent or adjacent piles: PCS piles, cased auger piles, large diameter bored piles (cased, or under support fluid) and micropiles.
secant or interlocking piles: cased auger piles or large diameter bored piles (under temporary and recoverable casing, or under support fluid).
• Tangent pile walls are only effective as soil-retaining structures.
• Secant pile walls are soil and water-retaining structures; if necessary, the wall must be stabilized using anchors
• Normally only one pile in two is reinforced in a secant pile walls
• A pile wall can have a significant vertical foundation load transfer function
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