Large diameter drilled piles

The methodology of making bored piles dates back to early 1849 c.e. As the new technology evolves, there are used of increasingly powerful equipment and the ability to support the excavation walls by bentonite or polymeric muds allows the construction of foundation piles up to 4 m in diameter and 100 m deep using this technology.
Amato Ltd. manufactures poles whose diameter can vary from 400 to 3000 mm, depending on the method of execution:

  • Dry-drilled piles;
  • Piles drilled in bentonite mud or with polymers, in loose soils where the mud pressure prevents the side walls of the borehole from collapsing;
  • Bored piles with provissory or final lining indicated for gravelly soils and consists of driving in steel pipes by rotation or vibroinfusion.

The equipment used are:

  • rotary equipment: consisting of a state-of-the-art tracked auger. Drilling is done by rotation with a telescopic rod, which can be “friction” for loose soils or clays, or “locking” for medium-hard compact soils. Telescopic rods currently on the market also make it possible to reach great depths because of the components of the steels used, which allow for the twisting necessary to prevent breakage of the elements especially when drilling in compact soils. The tools are generally buckets, propellers, core barrels. In special cases, such as the presence of bedrock or rocky layers, percussion tools such as a breaker chisel or biting bucket or the same tools with widia spikes will also be adopted. In particular types of soils such as gravels, sands or silts, temporary linings consisting of steel pipes, which can be inserted using the drill itself, or hydraulic vibrators driven by self-propelled cranes, or bentonite slurries or biodegradable polymers are used to prevent fragmentation of the borehole walls (the latter necessary if there are special constraints related to groundwater pollution or disposal of the waste material). The use of bentonite sludge requires adequate filtration where very sandy soils are present with the use of appropriate “desander.”
  • Biting bucket equipment: consisting of a crawler crane with a lattice boom that moves a valve bucket bite. The equipment is complemented by the temporary or final lining pipe, driven by a column-turning vice or vibrator carried by the same excavation crane or auxiliary.

    Method of execution:

    • drilling: a 3-5 m temporary covering called an avampozzo is initially laid. In the case of excavation with bentonite sludge, the bottom level must be maintained close to the work surface and at least 1 m above the water table;
    • Laying metal reinforcement: consisting of pre-assembled steel cages equipped with appropriate spacers to ensure centering of the reinforcement and sufficient concrete cover. The joining between the reinforcing bars of two contiguous cage elements by overlapping with clamps and ties;
    • Paving concrete: Through appropriate conveying tube (jet tube) from the bottom to the top. the tube is equipped at the upper end with a loading shake. Care must be taken to stop its footing at 25.50 cm from the bottom of the excavation;
    • in-process checks: Are control of tracking and preparation, control of excavation procedures, control of drilling mud, control of reinforcement, control of concrete and casting;
    • FINAL CHECKS: are load strength checks (load tests), nondestructive pile integrity checks (mechanical admittance tests), nondestructive pile integrity checks (sonic tests).