COLLEGE OF ENGINEERING, PUNE

PILE FOUNDATIONS AND DIAPHRAGM WALLSAKASH TILOKANI121420006Subject: Construction Techniques

CONTENTS• Introduction and Terms related to Piles• Classification of Piles• Load Bearing Piles and its types• Driving Load Bearing Pile• Ancillary Concepts• Diaphragm Walls

Introduction • Foundations used – Constraints like Large Design

Loads, Poor Soil at Shallow Depths, Property Line Constraints, etc.

• System used for other purposes like Coffer Dams and Bulk Heads

• Scope: Selection of Piles, Equipments used for driving, ancillary concepts

• Can be classified on several basis, scope; on the basis of use and materials

Important termsSr. No.

Term Description

1. Butt Upper end of the driven pile2. Cushion Material inserted between the ram of the

hammer and driving cap3. Cutoff Portion of pile removed from upper end of the

pile after driving4. Driving Cap Cover placed over the butt5. Embedment Length of the pile from G.L. to its tip6. Penetration Axial movement of the pile per hammer blow7. Pile bent Two or more piles driven together fastened

with bracings8. Tip Lower end of the pile9. Shoe Metal portion attached to the tip10. Overdriving Driving such that damage is caused to the pile

Classification

Piles

Load Bearing

Piles

Timber and

ConcreteSteel and Composit

e

Sheet Piles

Timber and

ConcreteSteel

Load Bearing Piles and Classification• Used to transmit structural loads to the hard

stratum• Suitable when shallow foundations are not

feasible due to various constraints• Classified on the basis of material, method of

constructing and method of drivingSr. No. Type of Pile Sub Classification

1. Timber (a) Treated(b) Untreated

2. Concrete (a) Precast – Pre stressed(b) Cast in Situ with

shells (c) Augered Cast in Situ

3. Steel (a) H section(b) Steel Pipe

4. Composite (a) Concrete and Steel(b) Plastic with steel pipe

core

Continued…11. Timber Piles• Made of trunk of trees, generally available in

lengths 15 to 45 feet, design loads are 10 to 60 tons

• Timber; Susceptible to decay and hence the use of treated timber

• Preservative such as salts and creosote used to reduce the rate of decay

• Untreated timber; Lesser life, used for temporary construction Quality Control

1. Check for minimum nominal circumference2. Check for straightness 3. Check for Knots

Continued…22. Concrete Piles• In general, can be either precast –

pre stressed or cast in situ• P-P piles shapes: square, cylindrical

or octagonal• Square and octagonal are casted in

horizontal forms, on casting bed• Cylindrical are casted in cylindrical

forms and spun for consolidation• Steam Curing is done for the

above, pre stressing done with strands, spiral reinforcements are provided

• Drawback: Reducing or increasing the length of piles, upon any requirement

Continued…3• It is advisable to use rammer with heavy ram and

low impact velocity when soft soils are encountered

• Driving cap should fit loosely around the top of the pile – prevention of torsional stresses

• Ends of the pre stressing strand or reinforcing must either be cut off flush with the top of the pile or the driving cap must be designed to contain threads

• To eliminate eccentricity, top must be perpendicular to the longitudinal axis

• It is important to avoid soil plug in case of cylindrical piles for structural stability reasons

Continued…4• Cast in situ piles can be constructed in two

fashions; by displacing the surrounding soil or by not displacing the surrounding soil

• First can be performed in two ways; concrete placed in hole previously driven in the ground or concrete placed in hole from which mandrel is removed

• Franki technique is a patented technique to perform the first

• Second is consonance with augered cast in situ piles

• ACIS piles are constructed by rotating a hollow shaft continuous flight auger into soil to a predetermined tip elevation

Continued…53. Steel Piles• Have higher initial costs, but lower

driving costs• Used when piles are to be driven

to greater depths, strength required is high and less displacement of the surrounding soil

• Can be of two types; H section or steel pipe piles

• H section is primarily used as end bearing pile, susceptible to deflection on striking boulders or other obstruction

• Used in the urban areas where heaving of surrounding soil may become a problem

• Available in small lengths where height or head room is not enough for driving, small lengths are welded together

Continued…6• Steel pipe piles can be hollow box or tubular in

shape• Most efficient friction piles• Can be close ended or open ended• Close ended are driven by conventional methods

and sections are joined with the help of internal sleeve

• Open ended are driven in the soil and the soil inside is removed by methods like bursts of compressed air, mixture of water and compressed or use of earth auger

Continued…74. Composite Piles• Used in some special situations• Special situations; hard driving conditions or warm marine

conditions• Can be of the types; concrete steel composite, steel concrete

composite and plastic steel composite• Concrete steel composite; top portion of pre stressed concrete

pile, and tip would be a steel H pile, suitable for marine conditions

• Steel concrete composite; Steel casing with hollow spun concrete core, resting on solid driving shoe, suitable for hard driving conditions

• Plastic steel composite; replaced creosote coating, Plastic piles consisting of steel hollow core, most suitable for fender systems

Driving Load Bearing Pile• Total resistance offered by the pile is the sum of

forces produced by friction and end bearing• Representative value for skin friction can be

obtained by determining the total force required to cause small increments

• The magnitude of end bearing is determined by driving button bottom pile test

• For large scale projects – test pile program should be conducted – cost effective

• Factors when selecting a method for driving piles; size and weight of pile, driving resistance, available space, noise restrictions

Test Pile Program• Initial site investigations give

information on soil characteristics and depths of strata capable of supporting the load.

• Used to arrive at more precise pile length and number of blows per foot by the hammer to attain desired bearing capacity

• Test piles are selected, which have length larger than predicted by borings for some reasons

• Static loads are applied by methods; static test weights or reaction pile method

• Static test weights are incrementally applied on the pile and relevant information is gathered

• Reaction pile method consists of steel H piles, placed in close proximity of the test pile and consequent gathering of information

Pile Driving Equipment• For driving piles, many types of

hammers are used, these are used to furnish energy required to drive pile, various types are as follows:

1. Drop hammer2. Single acting

steam/compressed air hammer3. Double acting steam

/compressed air hammer4. Differential acting

steam/compressed air hammer5. Diesel hammer6. Hydraulic impact hammer7. Vibratory drivers

Selection of Hammer• Several factors influence selection of piles; size

and type of pile, number of piles, character of soil, location of project, topography of site, type of rig available, land or water

• Hammer should be selected such that there is minimum practical cost

• In general, it is sensible to select largest hammer that can be used without overstressing

• Considerations must be specially given to crane

Supporting and Positioning Piles During Driving• Method necessary to position

the piles at proper location with required alignment or batter that will support the pile during driving

• Following methods are used for said purpose:

1. Fixed Leads2. Swing Leads3. Hydraulic Leads4. Templates• Other methods are1. Jetting Piles2. Spudding and Preaugering

Diaphragm Walls• Diaphragm walls are underground

structural elements commonly used for retention systems and permanent foundation walls.

• Diaphragm walls provide a water tight barrier and are constructed with a minimum back slope subsidence.

• They are formed from reinforced concrete and are constructed as normal cast-in-place walls with support, which become part of the main structure.

• They can also be used as deep groundwater barriers.

Advantages & Disadvantages• Can be installed through virtually

all soil conditions, to any plan geometry and to considerable depths.

• Can be constructed ahead of time and independent of other site activities.

• Can be constructed in relatively low headroom and in areas of restricted access walls can be quickly formed several hundred feet deep and through rock, with good control over geometry and continuity.

• They are relatively costly.

• They are also unsuited to strong soils conditions where penetration is slow and difficult due to the use of the slurry trench method.

Applications• As permanent and temporary foundation walls for

deep basements.• In earth retention schemes for highway and tunnel

projects.• As permanent walls for deep shafts for tunnel

access.• As permanent cut-off walls through the core of

earth dams.• In congested areas for retention systems and

permanent foundation walls.• Deep ground water barriers through and under

dams.

Slurry Trench Method• The panel dimensions 50 to 100 cm thick and up to 7m

height, extending to the excavation bottom. • The installation starts with the construction of shallow

concrete or steel guide walls. • The excavation is then made using special equipment,

such as the thin-grab clamshell. • Bentonite slurry is then pumped into the trench to

provide temporary support and a prefabricated reinforcing cage is lowered in.

• The bentonite slurry is then replaced by concrete and the sequence proceeds onto the next panel.

References• Construction Planning, Equipments and Methods

by Puerifoy, Schexnayder & Shapira• Soil Mechanics and Foundations by Dr. B. C.

Punmia & Ashok Kumar Jain• http://en.wikipedia.org/wiki/Deep_foundation• www.franki.co.gg/• Selecting Pile Construction Method using Fuzzy

approach, Zayed, T. M., Journal of Construction Engineering and Management, ASCE.

Thank You