Secant pile wall is formed by installing a series of secondary piles (high grade concrete with reinforcement) overlapping the primary piles (can be high or low grade concrete and sometimes reinforced). The overlapping/overcutting between secondary and primary piles are usually between 100 to 400mm depending on the pile depth and size.
Guide walls are normally installed for better positioning control as well as verticality control of secant piles.
A series of primary piles are installed first. The secondary pile is then installed in between two primary piles by overcutting the primary piles. Double wall casings with cutting bits on the bottom edge are used to install both the primary and secondary piles. This is critical for maintaining pile verticality (within 1:250) to ensure overcutting over the entire depth of the primary/secondary piles.
We have successfully installed a number of secant pile walls. Our highly skilled team have installed hard/hard (both primary and secondary piles using G40 concrete) secant pile up to 1500mm diameter to a depth of over 40m.