Cased CFA Piles (Double Rotary System)

It requires the use of heavy duty large piling rigs with high torque capacities.  The method requires the use of two rotary heads driving a heavy duty hollow-stem CFA auger in a clockwise direction into the top soil while at the same time rotating a casing in anticlockwise direction such that the toe of the auger and the bottom of the casing are at about the same level during the advancement of the drilling process.  Upon reaching the design pile depth and in a manner identical to CFA piles, the concrete is pumped through the CFA auger but this time constrained by the full length casing.  This helps maintain a perfectly circular pile shaft with a very tight control on verticality.

Secant piled walls are formed by interlocking reinforced concrete rotary bored piles. The piles are reinforced with either steel rebar or with steel beams and are constructed by either drilling under mud or using the Cased CFA piles using our double rotary drilling rigs such as the Liebherr LRB 255 & the LRB 355.  Alternate primary piles comprising of reinforced concrete are installed first, then secondary infill piles are installed in between primary piles, once the latter gain sufficient strength. Pile overlap is typically of the order of 100 to 150mm depending on the depth of the excavation and degree of ‘watertighntess’ required.