Bored piles represent the most common and oldest type of cast-in-place piles. With the advent of new replacement technologies and the problems related to the management of bentonite sludge, this work is placed in a niche, however significant, characterized by large diameters, 1200 mm and more, by extremely complex stratigraphy (including rock) or considerable depths.
The executive sequence is extremely simple: the excavation is carried out by removing the soil by means of biting buckets or other dedicated tools, the metal reinforcement is inserted first, then a casting tube to the bottom of the excavation and through the hopper at the top of the casting tube the concrete is inserted by progressively extracting the casting tube.
Depending on the geotechnical context and the presence or absence of water table, there are 3 main configurations:
self-supporting hole that involves dry excavation (not very common and not always accepted);
presence of water table that requires the use of a coating plate, usually vibro-infixed, at least for a portion of the length of the hole;
a non-self-supporting hole that requires either a total lining of the hole or the use of bentonite or polymer slurries.
In the case of interception of bedrock or other consolidated layer, or for the anchoring of the pile itself, special tools are fitted which work like a rock-breaking chisel.
It is common practice to protect the upper part of the hole with a metal plate (forecourt) to prevent erosion of the walls of the hole caused by the repeated passage of the excavation tools.
A variant of the drilled pile is the coring pile, characterized by the use of a core barrel as an excavation tool.
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