CPI-4 Piles

Piles which are drilled and concreted in situ, in which the walls being drilled are supported using temporary casing.

Execution

Excavation in soft and medium ground is completed using short propeller drills. In cases with harder ground, a tungsten carbide tipped drill is needed. In very hard, rocky ground a circular tungsten carbide tipped crown drill is used.

The main feature of the CPI-4 micropiles is that while they are being drilled, a temporary casing, or jacket, is put into the ground.

Once the desired depth is reached, the bottom of the excavation is cleaned using a scoop (‘bucket´).

Alter clearing the bottom a steel frame is introduced with the help of additional equipment (a crane). To guarantee the minimum necessary coverage it is raised 20cm above the base of the excavation and separators are used for correct centring.

Alter placing the steel frame the concreting begins. To pour the concrete into the hole properly, avoiding segregation or bleeding, a tremie tube is used. The tube is fed through the steel frame until the base of the hole is reached. Then the concrete is pumped, which should be of a fluid consistency. This being denser than the support fluid (bentonite slurry of polymer) which stays at the base, pushing the concrete to the surface. Then the concreting can start.

Whilst the concreting progresses, the tremie tube is simultaneously raised, taking care to always keep it two metres below the level of the fresh concrete. At the same time, the casing is removed, always keeping it below the level of fresh concrete. In this way, cuts in the concrete caused by displacement of the excavation walls can be avoided.

Once the concrete reaches ground level, the concreting ends.