PILE WORK AT DLF HOUSING PROJECT, NEWTOWN, KOLKATA

PRAKASH AGARWAL

SVNIT, Surat

PILE ? Definition: A long timber, concrete

or steel structural element that is driven or otherwise embedded into the ground for the purpose of transferring the load of a superstructure to deeper soil strata.

NEED OF PILES……… The growing need for housing and

construction has forced authorities and development agencies to exploit lands with poor soil characteristics.This has led to the emergence and development of pile foundations which transfers the load to deeper soil strata or rock of high bearing capacity, thus avoiding the shallow soil of low load bearing capacity.

NEED OF PILES………(Contd.) A structure can be founded on piles if

the soil immediately beneath its base does not have adequate bearing capacity. If the results of site investigation show that the shallow soil is unstable and weak or if the magnitude of the estimated settlement is not acceptable a pile foundation may is generally considered.

NEED OF PILES………(Contd.) Further, a cost estimate may indicate that a

pile foundation may be cheaper than any other compared ground improvement costs.

In the cases of heavy constructions, it is likely that the bearing capacity of the shallow soil will not be satisfactory, and the construction should be built on pile foundations.

FUNCTION OF PILES Transmit foundation loads to strata

beyond the practical reach of shallow foundations.

Anchor structures against uplift forces

Assist structures in resisting lateral and overturning forces.

CLASSIFICATION OF PILES Based on load transmission and

functional behaviour: 1. End bearing piles (point bearing piles) 2. Friction piles (cohesion piles ) 3. Combination of friction and cohesion piles Based on the type of material: 1. Timber piles 2. Concrete piles 3. Steel piles 4. Composite piles

CLASSIFICATION OF PILES (Contd.) Based on the effect on soil: 1. Driven pile 2. Bored pile

FACTORS INFLUENCING CHOICE OF PILE Location & Type of structure Ground conditions Durability Cost

EQUPIMENTS INVOLVED DRIVEN PILING : i. Direct push rig (type of drilling rig) ii. 3 drum winch iii. Hollow cylindrical tube of

required length and diameter iv. Pile shoe

DIRECT PUSH RIG

3 DRUM WINCH

THE HOLLOW STEEL TUBE

A GROUP OF PILE SHOES

EQUPIMENTS INVOLVED (Contd.) BORE PILING : i. Rig vii. Bentonite ii. Winch viii. Trimmie pipes iii. Baler ix. Hooper iv. Casing v. Chisel vi. Jet pipes

A RIG

WINCH

BALER

IRON CASING

CHISEL

JET PIPES

TRIMMIE PIPES

HOOPER

PROCESS OF DRIVEN PILE Locating the pile center and subsequent

placing of a pile shoe of required diameter and thickness over the center.

Centering and placing the hollow cylindrical tube over the pile shoe.

Continuous hammering of the tube by means of winch and drop hammer, leading to the formation of a bore for the pile.

Required depth being achieved, reinforcement and concreting follows.

PROCESS OF DRIVEN PILE (Contd.) Immediate pulling out of the tube

accompanied with ramming of the concrete at short intervals.

Shifting of the rig to the next pile center.

DRIVEN PILE SPECIFICATIONS Pile shoe: 1. Internal Dia = 490mm/640mm 2. Thickness = 12mm Hollow cylindrical tube: 1. Length = 26.950m/27.950m 2. Internal Dia = 450mm/600mm 3. Thickness = 20mm 4. Weight = 6 – 8 MT Rig height = 27m/28m

DRIVEN PILE SPECIFICATIONS (Contd.) Pile: 1. Depth = 25.250m/26.8m/27.4m 2. Diameter = 450mm/600mm 3. COL = 5.250m for 25.05m pile 4. Shaft length = 20m/21m 5. Bearing capacity = 60MT/120MT Time taken = 1–1.5 hrs (approx.)

PROCESS OF BORE PILE Centering of rig on pile point & turning

the designated area’s ground muddy and loose by adding water & continuous ramming with baler.

Inserting the iron casing upto 2-3m depth & replacing the baler with chisel.

Continuous up down movement of chisel marking the onset of soil cutting by turning the mud into slurry.

As chisel gets deeper into ground, jet pipes are attached at its top and on one another till required depth is achieved.

PROCESS OF BORE PILE (Contd.) All this time, the slurry comes out of the

bore due to & fro movement of chisel & jet pipes. Method known as direct mud circulation.

Replacement of chisel & jet pipes with a no. of trimmie pipes, used for washing the bore.

Bentonite used during washing for increasing soil cohesion & S.G. of slurry checked with hydrometer whether 1.1 or not.

PROCESS OF BORE PILE (Contd.) Reinforcement & feeding the

hooper at the top of the trimmie pipes with concrete.

Concreting being over, trimmie pipes are being lifted up accompanied with ramming at short intervals.

BORE PILE SPECIFICATIONS Dia. Of iron casing = 750mm Dia of chisel < 750mm Pile: 1. Depth = 42m 2. Diameter = 750mm 3. Shaft length = 39m 4. Bearing capacity = 250 MT Time taken = 12-13 hrs. (approx.)

REINFORCEMENT IN PILE The rebar beam cage consists of main

rods, helical rods, circular rods known as stiffner and cover blocks.

Helical rods provide more strength against tensile stresses.

Stiffner is provided for holding the main rods, thus keeping diameter of the cage constant throughout its length.

Cover blocks in helical rods provide exact fitting of the cage in the hollow cylindrical tube.

REINFORCEMENT IN PILE (Contd.) Some specifications of the cage: 1. Diameter = 430mm/580mm/730mm 2. Length = 20.590m/21.656m/39.821m 3. Interval between stiffners = 2m 4. Interval in helical rods = 150mm/200mm 5. Dia. of main rods = 12mm/16mm/20mm 6. Dia. of stiffners = 12mm/16mm/20mm 7. Dia. of helical rods = 6mm/8mm/10mm

BEARING CAPACITY OF PILE Formula for computing bearing capacity

of a driven pile: U = U = Ultimate Load N = No. of blows by hammer W = Wt. Of hammer in tons H = Fall of hammer in feet (usually 1m) L = Driven length in feet P = Set / blows in inch (10mm / 10 blows) Factor of safety = 3

50*

1

**

L

P

HW

L

N

FEATURES OF DRIVEN PILE Distribution of load is in

longitudinal direction. Process is faster. Around 1-1.5 hrs.

for a pile of dia. 600mm and depth 27m.

High soil compaction is achieved, especially in group piles.

Around 3 times less expensive than bore piles.

FEATURES OF DRIVEN PILE (Contd.) Bearing capacity is much lower. Max. dia. & depth achievable is

600mm and 29m respectively. Practiced outside city limits only. Source of noise pollution.

FEATURES OF BORE PILE Distribution of load is in longitudinal

as well as lateral direction. Bearing capacity is higher due to

more frictional resistance between soil and concrete column.

Max. dia. & depth achievable is more than 2000mm & 1000m respectively.

Preferred in rocky areas.

FEATURES OF BORE PILE (Contd.) Process is time consuming. Around

12-13 hrs. for a pile of dia. 750mm and depth 42m.

Compaction of soil not achieved. Practiced in city areas as creates

lesser noise. More expensive than driven piles.

READY MIX CONCRETE Cement Grade 43 & 53: The grade 43 n

53 corresponds to the avg. compressive strength attained after 6724 hrs in MPa of at least 3 mortar cubes of face area 15 sq. cm composed of 1 part cement, 3 parts of sand (conforming to IS 650:1966) by mass and P/4 (P is the % of water required to produce a paste of standard consistency as per IS standard) + 3% (of combined mass of cement + sand) of water, prepared and tested in the manner described in methods of physical test for hydraulic cement.

READY MIX CONCRETE (Contd.) 1. After 721 hrs: Not less than 23 MPa for 43 grade, 27 MPa for 53 grade. 2. After 1682 hrs: Not less than 33MPa for 43 grade, 37MPa for 53 grade. 3. After 6724 hrs: Not less than 43MPa for 43 grade, 53 MPa for 53 grade. M 25 Concrete: Gives strength of 25 N/sq.

mm after 28 days of its laying. For moderate environment, the min. cement content of M 25 concrete is 6 bags per cubic metre.

HEAVY EQUIPMENTS Batching Plant Transit Mixer Concrete Pump Excavator Hydraulic Mobile Crane Backhoe Loader

TRANSIT MIXER

CONCRETE PUMP

EXCAVATOR

HYDRAULIC MOBILE CRANE

BACKHOE LOADER