1.5 Piling and Piling Techniques

8/11/2019 1.5 Piling and Piling Techniques

1/18

PILING TECHNIQUES


2/18

Piling is a type of Foundation which is defined as a columnsupported type of foundation, may be cast in-situ or pre-cast.

It may be made of Timber, Concrete, Steel, or combination of

any of them.

Pile foundation is adopted when the loose soil extends to a

great depth.

The load is transmitted by the piles to the hard stratum below or

it is resisted by the friction developed on the sides of piles.

Piling process involves lifting and holding the pile into position

and driving until it stops due to hard strata or reaches to a

specified depth.

PILING


3/18


4/18

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.

END BEARING PILES


5/18

Friction piles obtain a greater part of their carrying capacity by

skin friction or adhesion. This tends to occur when piles do notreach an impenetrable stratum but are driven for some distance

into a penetrable soil. 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.

FRICTION PILES


6/18

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 and help to prevent dishing of the raft in the

centre.

SETTLEMENT REDUCING PILES


7/18

1. Displacement piles: Displacement piles cause the soil to bedisplaced radially as well as vertically as the pile shaft is

driven or jacked into the ground.

2. Non-Displacement piles:Non-displacement piles soil is

removed and the resulting hole filled with concrete or a pre-cast concrete pile is dropped into the hole and grouted in.

TYPES OF PILES


8/18

1. Rotary Bored Piling

Compact powerful trackand lorry mounted rotary bored

pile equipment enable Foundation

Piling to provide edge of

highway, bridge abutment and

restricted access bored piling

solutions.

Advantages: Fast

Cost Effective

On-site relocation

METHODS OF PILE DRIVING


9/18

Capabilities

Diameters: 350 - 1400 mm; depths up to 35 m. Oscillated casing, polymers or bentonite.

Alternative engineered solutions.

Applications Continuous bored pile walls.

Hard / soft secant bored pile walls.

Piling into rock or banded rock strata. Piling adjacent to roads and railways.

Installation of permanent liners and Kingpost

walls

ROTARY BORED PILING


10/18

It is the quietest form of

piling and is suitable for forming

piles in most types of soil. The

use of these techniques in low

headroom and restricted access

has in the past been limited to a

maximum of 300 mm. Advancesin rig technology have

revolutionised our capabilities.

2. FLIGHT AUGER BORED PILES


11/18

Capabilities

Low vibration.

Restricted access and head room.

Casing installation to 15 m and bored depth up to 30 m.

Diameters all sizes up to 600 mm

Applications

Restricted access sites noise and vibration sensitive work.

Inter-bedded sequences of clays and sands.

Water bearing cohesion less strata.

Bearing piles.

Small restricted access retaining walls

FLIGHT AUGER BORED PILES


12/18

Using sectional temporary casing tosupport unstable ground

Employed in a wide range of ground

conditions providing an effective solution to

the problems associated with pile installation

for restricted access and limited headroom

sites where high loads are to be supported.

Most components can be manuallyhandled and very little mechanical assistance

is require to negotiate stairways and corridors

for making tripod rigs.

3. TRIPOD BORED PILING


13/18

Capabilities

Diameters from 250 mm to 750 mm.

Depths up to 35 m

Sectional casing

Methods of installation of Piles Dropping weight

Diesel Hammer

Vibratory methods

Jacking Methods

TRIPOD BORED PILING


14/18

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

When driving a hollow pile tube the weight usually acts on aplug at the top of the pile tube, thus reducing any excess

stress along the length of the tube during insertion.

Variants of the simple drop hammer are the single acting and

double acting hammers.

These are mechanically driven by steam, by compressed air

or hydraulically

4. DROPPING WEIGHT HAMMER


15/18

In the single acting hammer the weight is raised by

compressed air (or other means) which is then released andthe weight allowed to drop. This can happen up to 60 times a

minute

The double acting hammer is the same except compressed air

is also used on the down stroke of the hammer. This type of

hammer is not always suitable for driving concrete piles

however

DROPPING WEIGHT HAMMER


16/18

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.

Although the ram is smaller than the weight used in the drop

hammer the increased frequency of the blows can make up for

this inefficiency.

This type of hammer is most suitable for driving piles throughnon-cohesive granular soils where the majority of the resistance

is from end bearing.

5. DIESEL HAMMER


17/18

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.

The vibration can be produced by electrically (/hydraulically)powered contra-rotating eccentric masses attached to the pile head

usually acting at a frequency of about 20-40 Hz. If this frequency

is increased to around 100 Hz it can set up a longitudinal

resonance in the pile and penetration rates can approach up to 20

m/min in moderately dense granular soils.

Disadvantage:

The large energy resulting from the vibrations can damage

equipment, noise and vibration propagation can also result in the

settlement of nearby buildings.

6. VIBRATORY METHOD OF PILE DRIVING


18/18

Jacked piles are most commonly used in

underpinning existing structures. By excavating

underneath a structure short lengths of pile can beinserted and jacked into the ground using the underside

of the existing structure as a reaction.

JACKING METHODS OF INSERTION

1.5 Piling and Piling Techniques

Documents

Transcript of 1.5 Piling and Piling Techniques