702Load-Bearing Piles

702.1 Description. This work shall consist of furnishing and driving concrete and steel load-bearing piles to the

minimum nominal axial compressive resistance and penetration required, at the location shown on the plans.

702.2 Material. All material shall be in accordance with Division 1000, Material Details, and specifically as

follows: Item Section/Specification Reinforcing Steel for Concrete 1036 Cast-In-Place Pile Shells (Thick Shell Type) Welded or Seamless Steel Pipe ASTM A 252 Modified Grade 3* Closure Plates AASHTO M 270, Grade 50 (ASTM A 709 Grade 50) Structural Steel (HP) Pile AASHTO M 270, Grade 50 (ASTM A 709 Grade 50) Fluted Pipe SAE-1010 or SAE-1015 Forged Steel Tips or Noses SAE-1020 Pile Point Reinforcement ASTM A 148, Grade 90-60 Galvanizing 1081, ASTM A 123 Field Galvanizing and Galvanizing Repair ASTM A 780** *Physical and chemical requirements shall meet ASTM A 572 Grade 50. **Zinc rich paints will not be allowed.

702.2.1 Cast-In-Place (CIP) Concrete Piles. Cast-in-place concrete piles shall consist of Class B-1 concrete

cast in pre-driven steel shells. The steel shells shall be in accordance with the shape, size and minimum shell thickness shown on the plans, or to an approved equivalent section. All material, proportioning, air-entraining, mixing, slump and transporting of concrete shall be in accordance with Sec 501. Steel shells shall be free from water, soil and other deleterious matter when concrete is cast in the shells.

702.2.2 Structural Steel (HP) Piles. Structural steel piles shall be of the size, weight and structural shape

shown on the plans. Piles shall not have a camber or sweep in excess of 1/8 inch multiplied by the length of pile in feet divided by five. Structural steel piles shall be stored such that damage to the piling does not occur.

702.2.3 Pile Point Reinforcement. Pile point reinforcement shall be furnished and installed on load-bearing

piles at locations shown on the plans. Pile point reinforcement for steel piles shall be furnished and installed in accordance with Sec 1080, except as modified herein.

702.2.4 Pile Length. The contractor shall be fully responsible for the lengths the contractor furnishes for driving

to obtain the specified minimum nominal axial compressive resistance and penetration. The pile lengths shown on the plans shall be considered approximate lengths.

702.2.5 Probe Piles. Probe piles shall be of the same material and size as the permanent piles. Probe piles shall

be of such length as to permit driving the tips to an elevation 10 feet below that indicated by plan lengths. Probe piles used as permanent piles in place shall conform to Sec 702.4.8.

702.2.6 Certification. For structural steel piles and shells for cast-in-place piles, the contractor shall furnish two

copies of a certification from the pile manufacturer or fabricator setting out the designated specification with which the material furnished complies.

702.3 Equipment.

702.3.1 Driving Equipment. Piles shall be driven with power-driven hammers, or by a combination of power-

driven hammer and water jets. Power-driven hammers will be defined as hammers operated by steam, air or diesel power. For determining the energy per blow of diesel power hammers without a fully enclosed ram, the manufacturer's energy rating for the hammer will apply and may be assumed equal to the ram weight times the stroke. If the contractor desires to check a diesel power hammer against an approved steam hammer on a specified type of pile at a particular site, the contractor may do so at the contractor’s expense, and the checked rating of the diesel-powered hammer will be used in determination of pile nominal axial compressive resistances at that site. Diesel hammers that have a fully enclosed ram shall be equipped with a gauge and accompanying charts which evaluate the equivalent manufacturer's rated energy being produced under any driving condition.

702.3.2 Leads. Pile driver leads shall be constructed in such a manner as to afford freedom of movement of the

hammer, and leads shall be held in position by guys or stiffener braces to ensure support to the pile during driving. Inclined leads shall be used for the driving of battered piles.

702.3.3 Followers. Followers may be used in driving piles only if approved in writing by the engineer. If a

follower is used, one pile of every group of ten shall be driven without a follower to determine the available nominal axial compressive resistance of the group.

702.3.4 Water J ets. Water jets used to aid in driving piles shall be sufficient in number to deliver a volume and

pressure of water at the jet nozzles that will freely erode the material adjacent to the pile. The use of water jets shall be discontinued before the final penetration is reached, and piles shall be driven to secure a final penetration of no less than 2 feet if the nature of the soil permits.

702.3.5 Hammer Energy. The contractor is responsible for determining the hammer energy required to

successfully drive the pile to the minimum tip elevation and to reach the minimum nominal axial compressive resistance specified on the plans. When specified in the contract documents, the contractor shall perform a drivability analysis to select an appropriate hammer size to ensure the pile can be driven without overstressing the pile and to prevent refusal of the pile prior to reaching the minimum tip elevation. The contractor shall plan pile driving activities and submit hammer size and hammer energy requirements to the engineer for approval before driving.

702.4 Construction Requirements.

702.4.1 Probe Piles. The contractor shall furnish and drive probe piles at locations specified. Where required,

probe piles shall be driven to refusal or to a capacity 50 percent greater than that shown on the plans. In all cases, probe piles shall be driven to at least the minimum tip elevation shown on the plans for permanent piles. If no minimum tip elevation is shown on the plans, piles shall have a tip elevation at least 10 feet below the bottom of the supported footing or 10 feet below the natural ground line, whichever is lower, unless specifically authorized otherwise by the engineer. Probe piles shall be driven with the same type of equipment as will be used for driving the permanent piles. Before driving probe piles, the excavation shall be completed to an elevation no more than 2 feet above the proposed grade at the point where a probe pile is to be driven. Probe piles not driven in a permanent location shall be cut off or pulled and backfilled as approved by the engineer.

702.4.2 Load-Bearing Piles. Load-bearing piles shall not be driven until after the excavation for the footing has

been substantially completed. The heads of piles shall be protected against damage during driving. The procedure incident to the driving of piles shall not subject piles to excessive and undue abuse. Steel shells and structural steel piles shall hold the original form without distortion after being driven and after adjacent piles have been driven. Any load-bearing pile broken or damaged by reason of internal defects, by improper driving, or driven outside of the pile’s proper location, shall be removed and replaced, or a second adjacent pile may be driven if this can be done without detriment to the structure, as determined by the engineer.

702.4.3 Preboring. Where piles are to be driven through more than 5 feet of compacted embankment that has

been in place for less than five years, holes shall be prebored entirely through the embankment to the lowest elevation of the natural ground line adjacent to the embankment, or as shown on the plans. The holes shall have a diameter no less than that of the pile. After the pile is placed in the hole and before driving begins, the space remaining around the pile shall be filled with sand or other approved material before and maintained full during the driving of the pile.

702.4.3 1 Other locations where preboring for piles will be required will be shown on the plans. At such

locations, holes shall be prebored to the elevation specified prior to pile placement. The holes shall have a diameter no less than that of the pile and shall be large enough to avoid damage to the pile being driven through the hole in hard material. The size of the hole shall be approved by the engineer before preboring is started. Pilot holes of lesser diameter than the pile shall not extend below the pile tip. For holes not prebored into hard rock, the hole shall be filled with sand or other approved materials prior to or after placement of the pile. For holes prebored into hard rock, the hole shall be filled with sand or other approved materials prior to placement of the pile. At all locations, the hole shall be maintained full with sand or other approved material during the driving of the pile. The pile shall then be driven in accordance with Sec 702.4.11.

702.4.4 Pile Placement Tolerances. Final position of piles shall be no more than 1/4 inch per foot from the

vertical or from the batter line shown on the plans. The maximum variation of the head of the pile from the position shown on the plans shall be no more than 2 inches, except that piles in footings entirely below the finished ground line may not vary more than 6 inches. All piles forced upward by the driving of adjacent piles or by any other cause shall be redriven to the required minimum nominal axial compressive resistance and penetration.

702.4.5 Pile Point Reinforcement. Each point shall be manufactured in one piece of cast steel. Pile points

furnished for cast-in-place concrete piles shall be attached to the pile as shown on the plans. Pile points for structural steel piles shall be furnished with the minimum point web and flange thickness at the location of attachment to the pile equal to the thickness of that portion of the pile being attached thereto multiplied by the factor (t) shown below with additional requirements as described herein. Material (t) ASTM A 148 Grade 90-601.6

702.4.5 1 The point shall extend onto the pile a minimum of 1/2 inch for both faces of the web and for the end

one-fourth of the inside face of each flange.

702.4.5 2 The web portion of the point shall protrude a minimum of 0.2 times the flange width below the pile

with the flange portion of the pile point transitioning to a protrusion depth of no less than the pile point flange thickness at the extreme ends.

702.4.5 3 The point shall be attached to the pile with a full penetration weld along each flange. Weld backing

shall be furnished for the total width of each flange.

702.4.5 4 The point extension onto the web of the pile may be omitted if alternating 1 1/2-inch x 1/4-inch fillet

welds are placed on each side of the web.

702.4.5 5 Welding of the point to the pile shall be by a certified welder in accordance with Sec 712.6 field

welding requirements. Properly dried low hydrogen electrodes of the E70XX series shall be used with adequate protection from the elements in accordance with Sec 1080. The contractor shall be fully responsible for the adequacy of welds during driving.

702.4.6 Splices. Full length piles shall be driven wherever possible and practical. If extensions and splices are

permitted or required by the engineer, all welding, including splicing of steel shells and structural steel piles, and support or reinforcing angles welded to steel piles, shall be in accordance with Sec 1080 and performed by a certified welder in accordance with Sec 712.6 field welding requirements using properly dried low-hydrogen E7018 electrodes that have been protected from the elements to maintain the dry condition. Steel shells for cast- in-place concrete piles shall be spliced as shown on the plans. Structural steel piles shall be spliced with a butt joint as shown on the plans. The contractor may furnish lengths of steel shells that incorporate no more than one splice per pile or structural steel piles that incorporate no more than one splice per pile for lengths up to and including 40 feet. No more than two splices will be permitted in each structural steel pile furnished for lengths exceeding 40 feet. In preparation of piles prior to driving, the use of individual sections less than 8 feet long will not be permitted. Additional field splices necessary to extend structural steel piles or steel shells to reach adequate bearing material shall be limited to one per pile, unless authorized by the engineer.

702.4.7 Cut-Offs. The tops of all piles shall be cut off square at cut-off elevations.

702.4.8 Protective Coatings.

702.4.8 1 Bitumen and Paint. Before the coatings are applied, steel shall be thoroughly cleaned. A

commercially available bituminous coating, as approved by the engineer, shall be applied heavily to steel shells and structural steel piles in end bents for a length of 3 feet below the bottom of the concrete cap. All exposed steel piles shall have a bituminous coating 3 feet below and one foot above the finished ground line. Unless otherwise specified in the contract documents, all other exposed surfaces of steel shells and structural steel piles, including bracing, shall be coated with one 6-mil thickness of an approved gray epoxy mastic in accordance with the epoxy mastic manufacturer’s recommendations. Protective coatings will not be required below the normal low water line or for galvanized piles and bracing.

702.4.8 2 Galvanizing. Steel shells for cast-in-place piles, structural steel piles, and structural steel bracing shall

be galvanized as shown on the plans and in accordance with this specification. All pile below the pile concrete encasement shall be galvanized down to an elevation as shown on the plans. At the contractor's option, the entire pile length may be galvanized. Repairs to the galvanized coating and field galvanizing shall be in accordance with this specification. Repairs and field galvanizing will not be required where the pile will be encased in concrete or below the limits specified herein. Galvanizing material shall be omitted or removed one inch clear of weld locations. The method used to omit or remove the galvanizing material shall be masking, grinding or other methods as approved by the engineer. If a weld location falls within an area where galvanizing is required, clean the weld area making sure to remove all welding slag. Then field galvanize the weld area in accordance with this specification.

702.4.8 3 Bitumen and paint protective coatings will not be required for galvanized piles and bracing.

702.4.9 Time Restrictions. Concrete footings shall not be placed on cast-in-place piles until at least 12 hours

after the last pile in the footing has been cast. No piling shall be driven within a radius of 20 feet of concrete that has not attained a minimum compressive strength of 1,500 psi. Compressive strength will be determined by tests performed in accordance with approved methods.

702.4.10 FHWA-modified Gates Dynamic Pile Formula. The following formula shall be used to determine

the nominal axial compressive resistance, P, of piles when other methods of determination are not specified in the contract documents: P = 1.75(E)0.5log10(10N) – 100 P = Nominal Axial Compressive Resistance measured during pile driving in kips E = Developed hammer energy in foot-pounds (Joules). This is the kinetic energy in the ram at impact for a given blow and may be assumed equal to the ram weight times the stroke. N = Number of hammer blows for 1.0 inch of pile permanent set in blows/inch.

702.4.10 1 The above formulas will be applicable only if:

702.4.10 2 For piles driven to a batter, the nominal axial compressive resistance, P, in the equations provided in

Sec 702.4.10 shall be divided by the pile batter factor, B, in order to calculate the value of N, the number of hammer blows for 1.0 inch of pile permanent set. B = 0.1 (10 - m), pile batter factor (1 + m2) m = the tangent of the angle of batter to a vertical line

702.4.11 Minimum and Maximum Limits of Pile Driving. Piles shall be driven to at least the minimum tip

elevation indicated on the plans. If no minimum tip elevation is shown on the plans, piles shall have a tip elevation at least 10 feet below the bottom of the supported footing or 10 feet below the natural ground line, whichever is lower, unless specifically authorized otherwise by the engineer. Piles shall be driven to attain a nominal axial compressive resistance determined in accordance with Sec 702.4.10 and no less than that shown on the plans as the minimum nominal axial compressive resistance.

702.4.11 1 Pile Driving to Hard Rock. Prior to driving structural steel piles, the contractor shall review the

boring logs to determine the depth at which rock may be anticipated. The contractor shall be attentive to the physical conditions associated with pile refusal on hard rock. When indication of hard rock occurs, in no case shall the pile be driven more than 3 blows when the hammer is operating at maximum rated energy and the penetration per blow is equivalent to or less than 10 blows per 0.5 inch. Driving shall cease immediately to avoid damage to the pile and to reduce the risk of injury.

702.5 Method of Measurement.

702.5.1 Probe Piles. Probe piles will be measured to the nearest linear foot of pile authorized and driven. For

galvanized pile, no separate measurement will be made for the part of the pile that is not galvanized.

702.5.2 Load-Bearing Piles. Piles in place will be the actual length of all piles, except probe piles, measured to

the nearest foot for that portion of each pile that remains permanently in the structure. For galvanized pile, no separate measurement will be made for the part of the pile that is not galvanized.

702.5.3 Preboring. Final measurement will not be made except for authorized changes during construction or

where appreciable errors are found in the contract quantity. Where required, measurement of prebored holes required under the provisions of Sec 702.4.3 will be made to the nearest linear foot of each hole specified or directed by the engineer. The revision or correction will be computed and added to or deducted from the contract quantity.

702.5.4 Pile Point Reinforcement. Pile point reinforcement will be measured per each.

702.6 Basis of Payment.

702.6.1 Probe Piles. Probe piles will be paid for at the contract unit price. Probe piles, if driven and used as

permanent piles in place, will be paid for as probe piles, and not as load-bearing piles in place.

702.6.2 Load-Bearing Pile. The accepted quantity of load-bearing pile in place will be paid for at the contract

unit price for each of the items included in the contract. No direct payment will be made for incidental items necessary to complete the work unless specifically provided as a pay item in the contract.

702.6.3 Pile Cut-Offs. No direct payment will be made for pile cut-offs.

702.6.4 Preboring. Preboring will be paid for at the contract unit price. No direct payment will be made for

backfilling.

702.6.5 Pile Point Reinforcement. Pile point reinforcement, where specified, will be paid for at the contract

unit price per each.

702.6.6 Splices. Splices may be required to extend a structural steel or steel shell pile to reach the minimum

nominal axial compressive resistance. Any additional splices authorized to achieve the minimum nominal axial compressive resistance will be paid for as an additional 8 feet of pile in place at the contract unit price.

702.6.7 Protective Coatings. No direct payment will be made for coating exposed surfaces of steel shells and

structural steel piles. Galvanized bracing in place will be paid for at the contract unit price for miscellaneous fabricated structural steel. Payment for coating the structural steel piles as described herein, and all material, excavation, labor, tools, equipment and incidentals necessary to complete the protective coating items will be considered completely covered under the contract unit price for other items.