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