Piles Flashcards
What are piled foundations?
Deep foundations which are generally long, slender column shaped elements which are usually made out of concrete or steel.
How do piled foundations work?
They work by passing through weak and compressible earth to stronger more compact ground which transfers the structural weight down to earth with sufficient bearing capacity.
What are different types of piles?
- Driven Piles
- Bored Piles
- Contiguous Piles
- Secant Piles
- Sheet Piles
What is driven piling?
- Long slender columns which have a predetermined shape
- Installed by hammering, vibrating or pushing the pile into the ground to the design depth.
What are the advantages of Driven Piles?
- Pre-fabricated so efficient on-site installation
- cost effective
- Produces less spoil
What are the disadvantages of driven piles?
- Not appropriate for ground with poor drainage qualities
- Can be extremely noisy and large vibrations
- Advance planning is required for the handling and transportation of piles.
What is contiguous piling?
-This is a series of adjacent piles constructed to form an earth retaining structure as a cantilever or a propped cantilever wall.
- consist of a row of successive unconnected cast-in-situ concrete piles constructed with small gaps between the adjacent piles
- formed using CFA or rotary bored piles.
What is Secant Piling?
- Formed by constructing reinforced piles that interlock, reinforced with either steel rebar or steel beams.
- Typically primary (female) piles are cast in situ, leaving space in between them. This is followed by secondary (male) piles being cut into the primary piles to form a continuous wall, generally with a typical interlock of around 150mm.
What are the two main types of foundations?
Shallow foundations - used when loads imposed by the structure are low relative to the bearing capacity of the soils
Deep foundations - used when the surface soil bearing capacity is not adequate to support the loads imposed by the structure so they need to be transferred to deeper layers with greater bearing capacity
What are strip foundations?
- A trench foundation where the concrete is poured into the excavated trench usually dug along the outline of the structure and under load bearing walls
When would you use strip foundations?
- when there is good load bearing capacity within the soil
- when the structure being built has light structural loads such as one or two storey domestic buildings
What are Pad foundations?
- Generally used to support the structural columns or framed structure
- Generally square or rectangle in shape and thick enough to transfer the load through the column onto the pad and then onto the bearing layer
- Usually reinforced to make foundation even stronger
When would you use Pad foundations?
- Suitable when the bearing capacity of the ground is sufficient at low depths
What are raft foundations?
- Formed by large concrete slabs that usually cover the footprint of the building
- Acts as the buildings foundation and the ground floor or basement slab
- Spread the load imposed by the above structure over a large area and onto the ground which the slab floats on top of
- Cost effective as they fulfill two jobs at once, GF slab and foundation
What are the advantages of Secant Piling?
- Increased wall stiffness compared to sheet piles
- Less noisy construction
- Can be installed in difficult ground
