Bored piles, also known as drilled shafts or replacement piles are deep foundation solutions that provide support for structures with heavy vertical loads. Through a combination of skin friction and end bearing resistance, they transfer their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics.
These piles are formed by excavating cylindrical shafts into the ground and replacing them with reinforced concrete which is poured in situ.
It is a highly specialized operation that is carried out by a bored piling contractor who has extensive knowledge and experience in bored pile construction and engineering in addition to soil and site conditions.
As opposed to displacement piles/ driven piles, where the soil is forced away by driving or screwing the pile, bored piles offer various advantages as follows:
Effective for top-down construction allowing for simultaneous deep basement excavation as well as superstructure erection, before the completion of basement excavation. Used in deep basement construction to form structural steel columns projecting from the lower basement level foundations up to the approximate ground level.
Heavy and extensive strutting system minimized as the plunge columns may incorporate connection fixing points to allow the attachment of struts or beams. Plunge columns are also used to support the basement floor slabs which prop the excavation sides in a permanent condition. By propping the excavation with the permanent basement floor slabs instead of temporary props, an efficient design for the basement is created.
Micropiles are deep foundation elements typically ranging between 150 mm to 350 mm in diameter. They are comprised of high-strength steel casing, rebar, and grout.
Micropiles are commonly used for replacing deteriorating foundation systems, renovation of structures, and slopes, or landslide stabilization. They do not rely on end-bearing capacity, so there is no need to establish the competency of rock beyond bond-depth. They can be installed quickly in virtually every type of ground and at various angles using highly adaptable and compact mobile drilling equipment.
Micropiles are generally used in the following circumstances:
Advantages of Micropiles: