5.Steel Piles
5.1General
[This section requires effective proof reading and altered as deemed necessary. It also requires a critical review in the light of more current practice, codes and specifications.
Be sure to include the sections on Fabrication of Steelwork, Painting, and Ground Conditions (Miscellaneous clauses).
This applies to the supply and driving of steel piles driven to a prescribed capacity.
Refer to the sections on Fabrication of Steelwork and Protective Treatment of Steelwork.
5.2Standards
Conform to the following standards unless specified otherwise:
AS 1163Cold-formed structural steel hollow sections
AS 1554.1Structural steel welding, Part 1: Welding of steel structure
AS 2159Piling – Design and Installation
AS/NZS 3678Structural steel - Hot rolled plates, floorplates and slabs
AS 3679.1Hot rolled structural steel bars and sections
AS 4100Steel structures
Comply with the additional requirements of this Specification.
Comply with the requirements of this Specification if they contradict clauses in the above Standards.
5.3Fabrication
5.3.1General
Comply with the sections on fabrication of steelwork.
Unless otherwise noted on the drawings;
- Use grade300 for hot-rolled steel.
- Use grade 250 for cold-formed steel.
Use full penetration butt welds to join piles.
[Insert the following clause where steel H - piles are specified.]
Accurately align the adjoining webs.
Grind flanges to a smooth profile.
[Insert the following clause where steel shell piles are specified.]
Use full penetration butt welds for longitudinal and transverse joins and rotate tube segments 90degrees to stagger longitudinal joins.
5.3.2Dimensional Tolerances
Lateral bow: less than 0.001 of the length of the pile.
[Insert the following clause where steel shell piles are specified.]
Maximum out of round tolerance: + or -0.015 of the diameter.
5.3.3On Site Welding
Do not use unqualified welders.
Do not use welders inexperienced in this type of work.
5.4Corrosion Protection
Conform to the section on protective treatment of steelwork.
Allow seven days after the application of the protective coating before installing piles.
Allow a minimum curing time of 2hours before installing or continuing to install a pile containing a section of freshly reinstated protective coating.
Obtain the paint manufacturer's recommendations as to the minimum cure time at various ambient conditions, and comply with that recommendation if greater than 2hours.
5.5Handling, Storage And Pitching Of Piles
Store all steel away from the ground and protect against corrosion.
Do not use excessively rusted steelwork in the work.
Do not drag coated piles along the ground.
Assume full responsibility for any pile or protective coating damage and bear all costs and delays involved in replacing the pile with a conforming one, or repairing the damage to the satisfaction of the Superintendent.
Support and handle piles such that the maximum dynamic stress in the steel sections is less than 175MPa.
5.6Pile Driving
5.6.1General – Hold point
Drive piles to the levels shown on the Drawings unless otherwise directed by the Superintendent.
Make allowance for such other levels as may be required due to variation in the subsurface conditions or the need to achieve the "minimum specified pile vertical strength".
Prebore, drill and fire, or jet to reach those levels if necessary. (Approval is required to use any of these techniques and will only be given if circumstances permit. The pile's strength and integrity must not be compromised.) See PREBORE, DRILL AND FIRE, JETTING section.
Minimum specified pile vertical strength is the lesser of:
nominal refusal: 25mm total penetration for the final 20blows (usually only controls for piles on rock), and
the required capacity nominated on the Drawings.
Cease driving if the average set per blow is less than 0.5mm.
[Modify the following if particular conditions yield any of the techniques unsuitable]
Do not use unapproved pile driving equipment.
Hold Point – Obtain Superintendent approval of the proposed pile driving equipment prior to any pile driving.
Approval will normally be given within 20 working days of receipt of a request if full details (of the proposed pile driving frame, hammer, leaders, helmet and cushion) are provided and the equipment is considered to be adequate for the purpose.
Do not drive any pile until it and its welds have been inspected and approved.
Carry out all pile driving in the presence of the Superintendent.
Clearly mark each pile with a scale of distances from the toe (with graduations at 500mm intervals) so that the pile penetration is immediately obvious.
Redrive any piles which lift as a result of driving adjacent piles.
Do not remove pile driver from the head of a pile without the Superintendent's approval.
5.6.2Tolerances
Keep within the following tolerances:
Variation in crosssectional dimensions:+50mm, -10mm.
Variation in position of pile head:75mm in any direction.
Variation from the designated alignment:20mm per metre.
Variation from the straight:2% of the length of pile in any direction.
Assume full responsibility for conforming with these tolerances.
Replace piles which do not conform with this specification or tolerances unless otherwise approved by the Superintendent.
Bear all costs and delays involved in replacing the piles and undertaking whatever steps agreed with the Superintendent to provide an adequate final structure.
5.6.3Piles Hammers
Do not use double acting hammers.
Use a ram with a mass exceeding that of the pile being driven, except that drop hammers shall be oneandahalf times heavier than the mass of the pile and shall be at least 2.5tonnes.
5.6.4Driving Requirements
Protect the top of the pile with a suitable helmet of substantial steel construction providing uniform bearing across the top of the pile and holding the pile centrally under the hammer. Take responsibility for and bear all costs, expenses and delays resulting from pile head damage and repair caused by driving.
Drive from a sufficiently rigid fixed frame to achieve the specified tolerances.
Use effective guidance to hold piles online during the initial stages of driving.
Do not force piles into position or alignment.
Do not overstress piles during driving.
Check the amount of force exerted on the pile by the pile frame shortly after commencement of driving and at regular intervals whilst driving.
Immediately release undue lateral forces from the piles.
Cease driving, withdraw the pile, fill the hole and redrive the pile if the pile would otherwise finish outside tolerances.
Drive piles continuously in the latter stages: delays are likely to cause premature "setup" and invalidate the results of pile driving formula.
Assume full responsibility for installing the specified piles and bear all costs and delays involved in replacing a pile damaged during driving with a conforming one, or undertaking whatever steps the Superintendent directs are necessary to provide an adequate final structure.
5.6.5Retesting Driving Resistance
Redrive to retest the driving resistance after a period of pile "setup" if directed by the Superintendent.
Retest at a time between one and seven days after initial driving.
Drive until the set of the last 5blows is greater than 50% of the previous 5.
Use the same equipment and record the same information as for ordinarily driving to set.
5.6.6Vertical Strength of Piles
The vertical strength of each pile shall be calculated from the following version of the Hiley Formula:
P=Ru=9810 x EF x EN x (MR + (E x E x MP))
FF x (S + 0.5 x (C1 + C2 + C3)) x (MR + MP)
where:
P=strength in kilonewtons kN.
Ru=ultimate dynamic strength in kilonewtons kN.
F=safety factor (use 4 to calculate the safe "working" vertical strength,
and 2.5 for the safe "ultimate" vertical strength)
EF=efficiency of fall of hammer
EN=delivered energy of hammer in tonnemetres/blow
S=final set of pile in mm (average of 10blows for steam, air and diesel
hammers, average of 5blows for drop hammers).
C1=temp. compression of pile head and cap in mm
C2=temp. compression of pile in mm
C3=temp. compression of ground in mm.
E=coefficient of restitution
MP=mass of pile, helmet and shoe in kilogram
MR=mass of hammer or ram in kilogram
Agree determination of coefficientsEF, E and C1 with the Superintendent: they are dependent upon the type of equipment used and the batter of piles.
Measure coefficientsC2 and C3 simultaneously with the set.
5.6.7Test Piles
[Use this clause if a complete static load test is specified.]
Supply, driving, and splicing requirements for test piles are the same as for production piles.
5.6.8Test Loading
[Insert this section if test loading is likely to be ordered, preferably use a schedule item for it. Nominate the piles to be tested on the drawings if possible.
Modify these clauses to suit particular conditions.]
Test the piles nominated by the Superintendent, unless particular piles are nominated on the Drawings.
Do not complete any other further piles until the test loading is completed and the Superintendent has given written approval to proceed.
Do not commence a load test without approval.
Approval will be given within 7working days of receipt of a written request if:
full technical details of the methods of applying loads and reactions and measuring deflections are provided, and
the proposed details indicate that the test will yield acceptably accurate and reliable results.
Apply a test load 1.5times greater than the vertical pile strength shown on the Drawings.
Measure deflections to an accuracy of + or -0.1mm.
Keep a continuous record of the movement of the top of the pile over the entire duration of the test.
Use intermediate load increments smaller than 100kilonewtons kN.
Measure deflection immediately after each load increment is applied.
Apply intermediate load increments as rapidly as possible.
Immediately after reaching full test load, keep it constant and record deflections at the following times:
15seconds
30seconds
1minute
2minutes
3minutes
4minutes
5minutes
30minutes
1hour
1hour intervals (at least 5) until deflection rates are less than 0.3mm per hour and reducing.
Allow the Superintendent free, safe access for observing and checking the test loading.
5.7Preboring, Drilling And Firing, Jetting
5.7.1General – Hold Point
[Need a note about these techniques.]
Do not use these techniques unless prior approval is obtained in writing from the Superintendent.
Hold Point -Obtain written superintendent approval of the technique to be used.
Approval will normally be given within 14days of receipt of a written request and full technical details of the proposals (if they indicate that the strength and integrity of the structure will not be compromised).
Assume full responsibility if the installed pile strength is deficient as a consequence of these special installation techniques.
Replace deficient strength piles with conforming piles as directed by the Superintendent. Alternatively, construct whatever works the Superintendent directs are necessary to provide an adequate final structure and compensate for the deficient piles.
Bear all costs and delays resulting from the rectification or replacement of deficient piles.
Do not prebore or jet for Hpiles.
Drive piles at least 1m below bottom of holes.
Backfill any remaining space with an approved granular material.
5.7.2Preboring
Bore using a hole of diameter 100mm smaller than the diagonal dimension of the pile.
Do not prebore to a greater extent than approved by the Superintendent.
5.7.3Drilling and Firing
Do not use more than the following explosive charge per hole:
W=8 x D2
where:W=mass of charge fired in any one delay period (grams)
D=the distance from the hole to the nearest structure or pile (metres).
[The following sentence probably needs a qualifying distance at which the velocity is measured.]
Ensure that the peak particle velocity of the shock wave is less than 50mm/second.
Fire holes singly.
5.7.4Jetting
Attach jets symmetrically to the pile.
Use a minimum of two per pile.
5.8Trimming And Preparation Of Pile Head
Remove coatings from all pile surfaces embedded more than 50mm in concrete.
Do not cast concrete against pile surfaces exhibiting loose rust and mill scale, or substances which are potentially deleterious to the bond between the pile and concrete.
<DoI Bridgeworks Master - Dec 2012
STEEL PILES