Deep foundation

Hamzah alib.arch. 3rd year

FOUNDATION The part of a structure which is below the ground and transmits all the loads from the super structure to the ground.

Foundations are broadly classified into two types:

Shallow foundation

Deep foundation

Shallow foundation• Shallow foundations are those founded near to the finished

ground surface; generally where the founding depth is less than the width of the footing and less than 3m.

• Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat and alluvial deposits, etc.

Deep foundation• Deep foundations are those founding too deeply below the

finished ground surface for their base bearing capacity to be affected by surface conditions, this is usually at depths >3 m below finished ground level.

   Deep foundations are used when there are weak (“bad”) soils near the surface or when loads are very high, such as very large skyscrapers.

   Deep foundations derive their support from deeper soils or bedrock.

Pile foundation Pile foundations are the part of a structure used to carry

and transfer the load of the structure to the bearing ground located at some depth below ground surface.

The main components of the foundation are the pile cap and the piles.

Piles are long and slender members which transfer the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity.

Pile caps are thick slabs used to tie a group of piles together to support and transmit column loads to the piles.   

Pile foundationAdvantages of pile foundation: Pile foundations are frequently needed because of the

relative inability of shallow footings to resist inclined, lateral, or uplift loads and overturning moments.

  Pile foundations are used in areas of expansive or

collapsible soils to resist undesirable seasonal movements of the foundations.

types of pile

piles

Displacement piles

Steel pile , concrete

spun piles etc.

Timber piles, precast RC

pile etc.

Replacementpiles

Bored piles

types of pileDisplacement Piles Piles which are driven are termed ‘Displacement Piles’

because their installation methods displace laterally the soils through which they are introduced.

Replacement Piles Piles that are formed by creating a borehole into which the

pile is then cast or placed, are referred to as ‘Replacement Piles’ because existing material, usually soil, is removed as part of the process.

Installation techniquesDropping weight The dropping weight or drop hammer is the most

commonly used method of insertion of displacement piles. A weight approximately half that of the pile is raised a suitable distance in a guide and released to strike the pile head.

Diesel hammer Rapid controlled explosions can be produced by the diesel

hammer. The explosions raise a ram which is used to drive the pile into the ground.

Installation techniques• VIBRATORY METHODS can prove to be very effective in

driving piles through non cohesive granular soils. The vibration of the pile excites the soil grains adjacent to the pile making the soil almost free flowing thus significantly reducing friction along the pile shaft. 

• JACKING PILES are the most commonly used methods in underpinning existing structures. By excavating underneath a structure short lengths of pile can be inserted and jacked into the ground.

Types of Pile

Pre Cast PileR.C. Square/Round Piles

Size :150mm to 400mmLengths :3m, 6m, 9m and 12mStructural Capacity :25Ton to 185TonJoints : WeldedInstallation Method :Drop HammerJack-In

Types of PilePre-stressed Concrete Spun Piles

Size : 250mm to 1000mm Lengths : 6m, 9m and 12m (Typical) Structural Capacity : 45Ton to 520Ton Joints: Welded Installation Method : Drop Hammer Jack-In

Types of Pile

Advantage of Pre Cast /Pre Stress Piles…..

Better Bending Resistance

Higher Axial Capacity

Better Manufacturing Quality

Able to maintain Higher Driving Stresses

Higher Tensile Capacity

Similar cost as RC Square Piles

Types of Pile

Steel H Piles

• Size :200mm to 400m

• Lengths : 6m and 12m

• Structural Capacity :40-1000ton

• Joints: Welded

• Installation Method :

• Hydraulic Hammer

• Jack-In

Types of Pile Bored pile is another type of reinforced concrete pile which is used to

support high building and bridge work which has heavy vertical load.

Bored pile is a cast-in-place concrete pile where the bored piles have to be cast on construction site, while other concrete piles like Spun Pile and Reinforced Concrete Square Pile are precast concrete pile which they’re cast in the factory.

it can be drilled upto 50metres depth of soil. The advantage of bored piling is its’ drilling method, little vibration and

lower noise level.

Types of PileBored Piles

• Size : 450mm to 2m

• Lengths : Varies

• Structural Capacity :

80Ton to 2,300Tons

• Installation Method :

Drill then Cast-In-Situ

Types of PileWood piles : Advantages   The piles are easy to handle and relatively inexpensive.   Sections can be joined together and excess length easily removed.Disadvantages  The piles will rot above the ground water level. Have a

limited bearing capacity. Can easily be damaged during driving by stones and boulders. The piles are difficult to splice and are attacked by marine

borers in salt water.

Types of PileEnd bearing piles End bearing piles are those which terminate in hard, relatively impenetrable material such as rock or very dense sand and gravel. They derive most of their carrying capacity from the resistance of the stratum at the toe of the pile.

Types of Pile Friction piles Friction piles obtain a greater part of their carrying capacity by skin friction or adhesion. Their carrying capacity is derived partly from end bearing and partly from skin friction between the embedded surface of the soil and the surrounding soil.

Types of PileSettlement reducing piles:

Settlement reducing piles are usually incorporated beneath the central part of a raft foundation in order to reduce differential settlement to an acceptable level. Such piles act to reinforce the soil beneath the raft.

Types of PilePiles in fill: Piles that pass through layers of moderately- to poorly-compacted fill will be affected by negative skin friction, which produces a downward drag along the pile shaft and therefore an additional load on the pile.