Drilling and pouring piles
Drilling and pouring piles are used in two directions: for the reinforcement of construction excavations or, in the case of a pilot foundation, to transfer the load from the superstructure onto deeper soil layers, which have a greater bearing capacity.
The cycle for performing the drilling and pouring piles is as follows:
- preparation but leveled and compacted site with bearing capacity 450 kN / m2 for access of a chain pilot machine at elevation, from which the pilots will be executed
- tracing of the pilots and positioning of the pilot machine
- drilling without / with siege depending on the hydrogeological conditions
- lowering of reinforcement- armopacket or double T profile
- contract concreting
- removal of siege pipes
- digging around the pilot's head
- breaking a pilot's head to reach uncompromised concrete
In the pilot reinforcement, three types of pilot system are possible depending on the hydrogeological conditions and the loads.: the pilots should be at a distance from each other, to tangle with each other or to crash into each other (secant pilots).
The clear distance between the pilots, when used to strengthen excavations, is limited in the normative documents. In some cases, shotcrete is applied to welded nets to prevent landslides between the piles..
The secant piles are performed in two strokes, as in the first bar the executed pilot is always unreinforced, and on the second bar the reinforced pilot is performed.
The pilot foundation is most widely used on a ground basis, composed of weak soils. With deep laid strong layers, the pilot foundation appears, as an alternative to shallow foundations, which require deep excavation, the corresponding strengthening, drainage and backfill.
Pilots transmit loads from the facility to the ground through peak resistance and ambient friction. To determine their load-bearing capacity, one of the most authoritative methods is to perform a test static load with a load at least twice above the calculated.