CONSTRUCTION TECHNOLOGY
INTRODUCTION OF PILE
PILE Pile - vertical COLUMN-LIKE structural member of foundation. - DEEP FOUNDATION category
Foundation
Shallow
Deep
Recap – Shallow Vs Deep Shallow
-Low-storey building. -Utilizing Area>Depth. -Soil Bearing Capacity. -Load-Stress Transfer.
Deep
-High-rise building. -Utilizing Depth/Shear Area. -Layer Contact/Soil Shear. -Point Load/Shear Transfer.
FUNCTION OF PILES Major 1.Transfer load (structure) to deep hard layer. 2.Resist uplifting forces of structure. 3.Resist horizontal load (pore pressure).
FUNCTION OF PILES (cont.) Minor 1.Permanent retaining wall. 2.Temporary support wall. 3.Compact loose, cohesion-less soil
Factor in Pile Selection • Nature of structure Necessity for pile foundation. • Location use Usage in land/water area (installation). • Surrounding condition Existing structure. • Soil condition Underground & soil condition. • Pile durability Presence of chemical & biological attack. • Cost & Availability Cost of transportation & operation.
CLASS OF PILE (LOAD) - End-Bearing Pile • •
Load transfer from structure to pile toe distribute to soil. Pile toe contact with hard soil layer or rock layer.
- Friction Pile •
Load transfer to surrounding soil by surface skin friction in cohesive soil. Pile have rough skin.
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Friction – End-Bearing Pile
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Combination of end-bearing and friction load transfer in cohesion-less soil. Pile have rough skin.
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CLASS OF PILE (LOAD) cont.
CLASS OF PILE (INSTALLATION) Displacement Pile - Driven, pushed, vibrated, screwed into ground. - Displacing original soil position without removal.
Replacement Pile - Hole bored on location and removal of soil. - Soil replaced with concrete & steel.
DISPLACEMENT PILE (DRIVEN)
REPLACEMENT PILE (IN-SITU)
COMPOSITE PILE
COMPOSITE PILE (cont.) - Combination of driven & cast in-situ pile installation. - Restrained ground condition and economical challenge for conventional pile. - Type • Prestcore Pile • Shell Pile • Cased Pile
COMPOSITE PILE (cont.) 1. Prestcore Pile • • • •
Utilizing precast and in-situ cast installation. Bored, driven & cast method. Performed inside bored hole. Identical to percussion bored pile.
Advantage - Suitable in un-drained (water-clogged) soil. - Prevent pile necking. - Suitable in headroom constraint operation.
COMPOSITE PILE (cont.) Installation 1. Forming bore hole by using percussion bored method (with/without tripod rig). 2. Core pile (precast) attached on special mandrel and reinforcement inserted before lowering core unit. 3. Bearing datum is consolidate and pressed by raising and lowering the pile core. 4. Lining tube removal and grouting are aided by compress ed air, in addition to expel water.
COMPOSITE PILE (cont.)
COMPOSITE PILE (cont.) 2. Shell Pile (West Shell Pile) • • • •
Utilizing the precast concrete shell attached to mandrel. Driven and Cast method. Permanent shell placement. Soil densification occur.
Advantage - Easy inspection of internal shaft. - No water & soil interruption during casting. - Outer shell resist chemical and biological attack. - Increase soil stability in term of density.
COMPOSITE PILE (cont.) Installation 1. Assembly - Mandrel attached inside the shell shaft. - Steel band (sleeves) install at each shell joint. - Attaching pile shoes (tip). 2. Driven - Assembly driven to required depth. - Applying drop hammer method.
COMPOSITE PILE (cont.) 3. Mandrel withdrawal. - Mandrel disconnected from the shell. - Shell and shoes left to integrated with soil. 4. In-situ casting. - Inserting prefabricated steel reinforcement. - Concrete filling and compacting.
COMPOSITE PILE (cont.)
COMPOSITE PILE (cont.) 3. Cased Pile • • • •
Using steel casing. Jointed connection is butt-welded. Utilizing internal drop hammer. Cased exposed with corrosion.
Advantage - Easy inspection of internal shaft. - No water & soil interruption during casting. - Increase soil stability in term of density.
COMPOSITE PILE (cont.) Installation 1. Assembly - Steel casing placed on guide frame. - Pile shoes may/not requires. - Each case jointed by butt-welded. 2. Driven - Pile driven by internal drop hammer. - Guide frame hold the case from derail.
COMPOSITE PILE (cont.) 3. Casting - Case filled with concrete. - Overall steel reinforcement may/not needed. - Extruding bonding bar attached at top.
COMPOSITE PILE (cont.)
PILE TESTING Objective - Measure pile physical characteristic. - Determine the suitability of pile. - Assessing pile safety and stability in long term projection.
Testing - Load Test (LT) - Cross-hole Sonic Logging (CSL) - Sonic Integrity Test (SIT)
PILE TESTING (cont.) 1. Load Test (MLT) •
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Test location determine based on the recorded soil condition. Number of pile determine by pile size, category, usage and capacity.
Common Type -
Static Load Test Dynamic Load Test Statnamic Load Test
PILE TESTING (cont.)
PILE TESTING (cont.) COMPARISON Test
•Static
•Dynamic
•Statnamic
Duration
•Long
•Short
•Short
Cost
•Expensive
•Cheap
•Moderate
Load
•Increment load placement. •Slow pressure.
•Single hammer drop. •Sudden impact
•Single internal combust drop. •Sudden impact
Assessment •Pile settlement
•Shaft resistance •End bearing •Shape integrity •Strain
•Shaft resistance •End bearing •Shape integrity •Strain •Crushing
Capacity
•Working load (sudden)
•Ultimate load (sudden)
•Bearing capacity
•Working load (slow)
PILE TESTING (cont.) 2. Cross-hole Sonic Logging (CSL) - Verify structural integrity and soundness of pile. - Needs prior placement of PVC tube during casting (water-filled). - Sonic pulse emit from signal generator and waveform is logged. - Result could be displayed in 3D Crosshole Sonic Tomogrphic Imaging.
PILE TESTING (cont.)
PILE TESTING (cont.) 3. Sonic Integrity Test (SIT) -
Most expensive method (equipment cost). Suit for any RC pile. Very fast analysis. Able to detect crack and early imperfection.
PILE TESTING (cont.)
Driven Piles – Pile Installation Pile driving methods: 1. Dropping weight (Impact hammers) 2. Vibration (Vibratory hammers)
Impact hammers pile driver: drive the piles into the soil, at the same time compacting surrounding ground and produce dense mass & enhance bearing capacity. water presence in the soil leads to a reduction in total bearing capacity & pile must be design for this. blow count is the number of times the pile must be struck until penetrate at required depth. No special casing required and no delays related to concrete curing. Immediate used when driven through water, can be installed to create temporary work platforms, and used in a large diameter form in earthquake-prone regions.
Diesel hammers pile driver weight is the piston, and apparatus connects to top of pile is the cylinder. pile driving started by having the weight raised by additional means – use cable from crane to hold which draws air into cylinder. diesel fuel injected into the cylinder and the weight is dropped, allow to fall by gravity. weight of the piston compresses air/fuel mixture, when mixture ignites, transferring energy of falling weight to the pile head, driving weight back up. rising weight draws fresh air and cycle starts over.
Hydraulic hammers pile driver • Modern type of piling hammer used in place of die sel hammers for driving piles. • More environmentally acceptable, generate less noise and emissions. • Extremely efficient by providing high production rates to get the job done quickly and cost effectively. • The blow rates are adjustable to optimise the pile driving performance in all conditions while ram weight can be changed to accommodate different pile type.
Vibratory pile driver system of counter-rotating eccentric weights, powered by hydraulic motors, designed to cancel out horizontal vibration, while vertical vibration transmitted into pile. lifted and positioned over the pile by means of an excavator or crane, fastened the pile by a clamp. Vibratory hammer can either drive in or extract a pile.
Displacement Piles – Driven Piles Materials of the pile are timber, concrete & steel. Advantages of the driven piles – inspected & checked structural member before driven into the ground. Disadvantages - when cutting off unwanted pile or addition of extra lengths become very expensive.
Timber Piles • May be circular or square (225x225mm to 600x600mm) in cross section. • To restrict the pile head from brooming due to the overdriving, iron ring 25 mm less in diameter than pile head is provided at the pile top. • To facilitate driving, the lower end of pile is pointed and provided with cast iron conical shoe to prevent splitting. • The best spacing is 90 cm c/c to maintained friction al resistance. • Driven into the soils which are either permanently wet or dry, remain in good condition.
Timber Piles • When subjected to alternate dry & wet conditions due to variations in ground water level, they get decayed. • Cut a little below the lowest watermarked and capped with concrete. • If timber capping is used, the cap should be permanently under water.
Precast Concrete Piles • Used where soft soils overlaying a firm layer are encountered. Lengths up to 18m with section sizes ranging from 250x250mm to 450x450mm carrying loadings up to 1000kN. • Function of reinforcement to resist the stresses produced during handling, driving and loading which pile is totally expected to overcome.
Precast Concrete Piles Available Precast Concrete Piles are: Precast Reinforced Concrete Piles – made of concrete cast in uniform section and reinforced with steel bars before driving into ground. Precast Pre-tensioned Concrete Piles - made of concrete cast in uniform section and reinforced with pre-stressing steel before driving into ground. Precast Pre-tensioned Spun Concrete Piles – hollow pile made of concrete cast by centrifugal spinning and reinforced with pre-stressing steel before driving into ground.
Precast Reinforced Concrete Piles
Precast Pre-tensioned Concrete Piles
Precast Pre-tensioned Spun Concrete Piles
Precast Concrete Piles Problem encounter when using pile in urban area: Transporting complete length of pile through narrow or congested streets. Driving process can cause unacceptable noise and vibration. Many urban sites are congested, making it difficult to manoeuvre long piles length around the site.
Steel Pile 2 main types of steel pile usually use:H-section pile ďƒ˜ in the form of wide flange sections. Do not cause large displacement of the soil, useful where upheaval of surrounding ground would damage adjoining property or where deep penetration required through loose or medium dense sands. ďƒ˜ High tendency to bend on weak axis during driving. Also has low penetration resistance in loose sandy soil.
Upheaval of soil
H-section pile
Steel Pile 2 main types of steel pile usually use:Steel box pile ďƒ˜ fabricated by welding together steel plates to form hollow piles capable of carrying very high compressive loads or lateral loads.
Driven and Cast-In-Place Piles • Construction begin by driving a closed-ended hollow steel casing either with a plug or loose shoe into the soil to the required depth. • A reinforcement and concrete is filled into the hollow tube. This case may be left permanently or withdrawn (temporarily). • Suitable where length of pile required varies. • Economically formed in diameter of 300 to 600mm and can carry loads up to 1300kN. • Required heavy piling rig, open level site and site where noise is restricted.
Franki driven in-situ p iles
Pile formed by boring a hole in the soil, thus removing a column of soil and replace it with in-situ concrete.
Suitable to use in sites where piling work to be carried out close proximity to existing building or where vibration or noise restricted. It is carried out by dropping a heavy cutter to dig into the ground and then raising and remove the spoil material that it bring with it.
Advantages
Length can be readily varied to suit varying ground c
Disadvantages
Susceptible to waisting or necking in squeezing ground.
ondition. •
Soil remover in boring can be inspection and if necessary sampled or in situ test made.
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Concrete is not places under ideal condition and cannotbe subsequently inspection.
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Can be installed in vary large diameter
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Water under artesian pressure may pipe up pile shaft washing out cement.
Can be installed in vary long length.
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Boring method may loosen sandy and gravelly soils.
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Absence of noise and vibration will not disturb adjacent piles or structures.
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Not suitable especiallyin river and for marine structures.
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Offer higher capacities with potentially better economics than driven piles.
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May cause loose of ground in cohesionless soil, leading to settlement of adjacent structures.
• Due to ground water movements. • Washing away some of the concrete. • Reducing the effective diameter of the pile shaft and the cover of concrete over the reinforcement.
• The upward movement of the ground. • Caused by displacement of the soil by the drive tube. • Can cause tension failure in the shafts of adjacent piles already driven.
• Worst case lifting of the completed piles. • Can be minimized by the enlarged base of the piles and anchoring the piles against uplift.
- Steel tube of length (1 to 1.4m) screwed together is sunk by extracting the soil from within the tube liner using percussion cutters. - The tube liner normally sink under its own weight but can also be driven in with slight pressure using hydraulic jack.
- When correct depth achieved, a cage of reinforcement is placed within the liner and then filled it with concrete. - Tamping is carried out as the liner is extracted by using a winch or hydraulic jack operating against a clamping collar fixed to the top of the steel tube lining.
- An internal drop hammer can also be used to tamp and consolidate concrete but usually compressed air is used.
Suitable for most cohesive soil such as clay. Formed using an auger which may be operated in conjunction with the steel tube liner. This auger is normally mounted on a lorry or tractor, raised to the surface and separate the helix to the side of the bore hole where the spoil is removed. If flight auger is used, the spiral motion will brings the spoil to the surface.
Rotary Drilling
with kelly – Cased Rotary Drilling using flight auger –
Continuous Flight Auger
Types of
Rotary Drilling with
Rotary Bored
kelly – Borehole
Piles
Supported by
System Rotary Drilling using
twin rotary head – Front of Wall
Hydrostatic Pressure
Standard which is cast-in-place pile.
Use where site conditions are restricted. Vibration free drilling. Casing installed by rotary drive.
Casing oscillator can be used for larger pile diameters and gre ater depths. Pile diameter generally 600 –1800 mm.
Depth generally up to 40 m but greater depth possible.
Vibration free drilling. No casing required. Started casing used for top section only.
Wall of borehole supported by Bentonite or Polymer Slurry. Borehole diameter generally (400-2400mm).
Depth generally up to 40m (but greater depths possible). Vertical piles only.
Main applications : For all types of soil, larger diameter piles
Suitable for all types of soil and on restricted sites. Vibration free and can be installed against existing wall. Continuous flight auger and casing installed simultaneously by counter rotating twin rotary drives.
Pile diameter from 305 to 550mm and depth generally up to 15m.
**CFA : Continuous Flight Auger
All types of soil and at restricted sites. Vibration free. Reinforcement can be pushed or vibrated into the fresh concrete. Diameter from 400 – 1000mm. Depth generally up to 18 m.
Using crawler crane and casing oscillator.
Main soil – sand and gravels with high demands on casing technology Used chisels to break up bedrock and boulders. Pile diameter ranging from 620-2000mm. Depths generally up to 50m.