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 of 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:
- Suitable for all site conditions
- Piles of variable lengths can be executed
- Less disruption to adjacent soils
- Vibration is relatively low, reducing disturbance of adjacent piles or structures. Hence, more suited for urban areas.
- For many design situations, bored piles offer higher capacities with potentially better economics than driven piles.
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 the deteriorating foundation systems, renovation of structures, slope 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:
- Difficult ground conditions such as natural or man-made obstructions
- Sensitive ground with adjacent structures
- Limited access or low headroom
Advantages of Micropiles:
- Cost-effective as they help shorten the project timeline
- Allow facility upgrades with minimal disruption to normal operations
- Improves the ground
- Offer high skin friction