1、Section 4 DRIVEN FOUNDATION PILES 4.1 DESCRIPTION This work shall consist of furnishing and driving foun- dation piles of the type and dimensions designated on the plans or in the special provisions including cutting off or building up foundation piles when required. This specifi- cation also covers
2、 providing test piles and performing loading tests. Piling shall conform to and be installed in accordance with these specifications, and at the location, and to the elevation, penetration, and bearing capacity shown on the plans or as directed by the Engineer. Any improperly driven, broken, or othe
3、rwise defective pile shall be corrected to the satisfaction of the Engineer by removal and replacement, or the driving of an addi- tional pile, at no extra cost. Except when test piles are required, the Contractor shall furnish the piles in accordance with the dimensions shown on the plans or specia
4、l provisions. When test piles are required, the pile lengths shown on the plans are for estimating purposes only and the actual lengths to be fur- nished for production piles will be determined by the En- gineer after the test piles have been driven. The lengths given in the Engineers order list wil
5、l include only the lengths anticipated for use in the completed structure. The Contractor shall, without added compensation, increase the lengths shown or ordered to provide for fresh heading and for such additional length as may be necessary to suit the method of operation. 4.2 MATERIALS 4.2.1 Stee
6、l Piles The structural steel used for foundation piling shall conform to the Specification for Structural Steel for Bridges, AASHTO M 270 (ASTM A 709) Grades 36,50, or 50W, or to the Specification for Piling for Use in Ma- rine Environment, ASTM A 690. 4.2.1.1 Painting Unless otherwise provided, whe
7、n steel piles or steel pile shells extend above the ground surface or water sur- face they shall be protected by the paint system specified for painting new steel in a high pollution or coastal envi- ronment as described in Section 13, “Painting.” This pro- tection shall extend from an elevation 2 f
8、eet below the water or ground surface to the top of the exposed steel. 4.2.2 Timber Piles Timber piles shall conform to the requirements of the Specification for Wood Products, AASHTO M 168. Tim- ber piles shall be treated or untreated as indicated on the plans or in the special provisions. Preserva
9、tive treatment shall conform to the requirements of Section 17, “Preserv- ative Treatment of Wood.” The method of storing and handling shall be such as to avoid injury to the piles. Special care shall be taken to avoid breaking the surface of treated piles. Canthooks, dogs, or pike-poles shall not b
10、e used. Cuts or breaks in the surface of treated piling and bolt holes shall be treated as specified in Article 16.3.3, “Treated Timber.” 4.2.3 Concrete Piles Concrete piles shall consist of either precast concrete piles or cast-in-place concrete piles cast in steel shells. Portland cement concrete
11、shall conform to the require- ments in Section 8, “Concrete Structures,” and unless an- other class is shown on the plans or specified, concrete shall be Class A. Reinforcing steel shall conform to the re- quirements of Section 9, “Reinforcing Steel,” and pre- stressing shall conform to the requirem
12、ents of Section 10, “Prestressing.” Steel shells for cast-in-place concrete piles shall be of not less than the thickness shown on the plans. The Con- tractor shall furnish shells of greater thickness if necessary to provide sufficient strength and rigidity to permit dri- ving with the equipment sel
13、ected for use without damage, and to prevent distortion caused by soil pressures or the driving of adjacent piles. The shells shall also be water- tight to exclude water during the placing of concrete. The shells may be cylindrical or tapered, step-tapered, or a combination of either, with cylindric
14、al sections. 489 490 HIGHWAY BRIDGES 4.3 4.3 MANUFACTURE OF PILES 4.3.1 Precast Concrete Piles 4.3.1.1 Forms Forms for precast concrete piles shall conform to the general requirements for concrete form work as provided in Section 3, “Temporary Works.” Forms shall provide ac- cess for vibration and c
15、onsolidation of the concrete. 4.3.1.5.1 Working Drawings The Contractor shall submit two sets of working drawings to the Engineer at the job site for prestressed concrete piles. Said drawings shall show the pile dimen- sions, materials, prestressing methods, tendon arrange- ment and prestressing for
16、ces proposed for use and, any addition or rearrangement of reinforcing steel from that shown on the plans. Construction of the piles shall not begin until the drawings have been approved by the Engineer. 4.3.1.2 Casting 4.3.1.6 Storage and Handling Handling and placing of concrete shall conform to t
17、he requirements of Section 8, “Concrete Structures,” and these specifications. Special care shall be taken to place the concrete so as to produce satisfactory bond with the reinforcement and avoid the formation of “stone pockets,” honeycomb, or other such defects. To secure uniformity, the concrete
18、in each pile shall be placed continuously and shall be compacted by vibrating or by other means acceptable to the Engineer. The forms shall be overfilled, the surplus concrete screeded off, and the top surfaces finished to a uniform, even texture simi- lar to that produced by the forms. 4.3.1.3 Fini
19、sh Portions of piling exposed to view shall be finished in accordance with the provisions governing the finishing of concrete columns. Other piling shall not be finished ex- cept as set forth above. Removal of forms, curing, storing, transporting, and handling of precast concrete piles shall be done
20、 in such a manner as to avoid excessive bending stresses, cracking, spalling, or other injurious results. Piles to be used in sea water or in sulfate soils shall be handled so as to avoid surface abrasions or other injuries exposing the interior concrete. 4.3.2 Cast-in-Place Concrete Piles 4.3.2.1 I
21、nspection of Metal Shells At all times prior to the placing of concrete in the driv- en shells, the Contractor shall have available a suitable light for the inspection of each shell throughout its entire length. 4.3.2.2 Placing Concrete 4.3.1.4 Curing and Protection Concrete piles shall be cured as
22、provided in Section 8, “Concrete Structures,” and these Specifications. As soon as the piles have set sufficiently to avoid damage, they shall be removed from the forms and stacked in a curing pile separated from each other by wood-spacing blocks. No pile shall be driven until at least 21 days after
23、 casting and, in cold weather, for a longer period as determined by the Engineer. Concrete piles for use in sea water or sulfate soils shall be cured for not less than 30 days before being used. Concrete shall be protected from freezing until the compressive strength reaches at least 0.8 f;. 4.3.1.5
24、 Prestressing Prestressing of concrete piles shall conform to the pro- visions of Section 10, “Prestressing.” No concrete shall be placed until all driving within a radius of 15 feet of the pile has been completed, or all driving within the above limits shall be discontinued until the concrete in th
25、e last pile cast has set at least 5 days. Concrete for cast-in-place piles shall be dense and homogeneous. In lieu of the provisions concerning vibration of concrete as specified in Article 8.7.4, vibra- tion or rodding of concrete for cast-in-place piles will only be required to a depth of 5 feet b
26、elow the ground surface. Concrete shall be placed for each pile in a single continuous operation with the flow of concrete directed down the center of the pile so as to consolidate the concrete by impact. Accumulations of water in shells shall be removed before the concrete is placed. After the conc
27、rete has hardened, the top surface shall be cut back to remove laitance and to expose the aggregate as specified in Article 8.8. 4.4 DIVISION II-CONSTRUCTION 49 1 4.4 DRIVING PILES 4.4.1 Pile Driving Equipment Driving equipment that damages the piling shall not be used. All pile driving equipment, i
28、ncluding the pile driving hammer, hammer cushion, drive head, pile cushion and other appurtenances to be furnished by the Contractor shall be approved in advance by the Engineer before any driving can take place. Pursuant to obtaining this ap- proval, the Contractor shall submit, at least 2 weeks be
29、- fore pile driving is to begin, a description of pile driving equipment to the Engineer. Whenever the bearing capacity of piles is specified to be determined by Method B, “Wave Equation Analysis,” the Contractor shall also submit calculations, based on a wave equation analysis, demonstrating that t
30、he piles can be driven with reasonable effort to the ordered lengths without damage. The following hammer efficiencies shall be used in a wave equation analysis: Hammer Type Efficiency in Percent Single acting aidsteam 67 Double acting aidsteam 50 Diesel 72 In addition to the other requirements of t
31、hese specifi- cations, the criteria which the Engineer will use to evalu- ate the driving equipment consists of both the required number of hammer blows per inch and the pile stresses at the required ultimate pile capacity. The required number of hammer blows indicated by calculations at the require
32、d bearing capacity shall be between 3 and 10 per inch for the driving equipment to be acceptable. In addition, for the driving equipment to be acceptable, the pile stresses, which are indicated by the calculations, to be generated by the driving equipment shall not exceed the values where pile damag
33、e impends. The point of im- pending damage in steel piles is defined herein as a com- pressive driving stress of 90% of the yield point of the pile material. For concrete piles, tensile stresses shall not ex- ceed 3 multiplied by the square root of the concrete com- pressive strength, fi, plus the e
34、ffective prestress value, i.e., (3 + prestress), and compressive stresses shall not exceed 85% of the compressive strength minus the ef- fective prestress value, i.e. (0.85 f, - prestress). For tim- ber piles, the compressive driving stress shall not exceed three times the allowable static design st
35、rength listed on the plans. These criteria will be used in evaluating calcu- lated results to determine acceptability of the Contractors proposed driving system. During pile driving operations, the Contractor shall use the approved system. Any change in the driving system will only be considered aft
36、er the Contractor has submitted revised pile driving equipment data and calculations. The Contractor will be notified of the acceptance or rejection of the driving system changes within 7 calendar days of the Engineers receipt of the requested change. The time required for submission, review, and ap
37、proval of a revised driving system shall not constitute the basis for a contract time extension to the Contractor. Approval of pile driving equipment shall not relieve the Contractor of his responsibility to drive piles, free of damage, to the bearing and tip elevation shown on the plans or specifie
38、d in the special provisions. 4.4.1.1 Hammers 4.4.1.1.1 General Piles may be driven with a drop hammer, an aidsteam hammer, or diesel hammer conforming to these specifica- tions. Pile driving hammers, other than drop hammers, shall be of the size needed to develop the energy required to drive piles a
39、t a penetration rate of not less than 0.10 inch per blow at the required bearing value. 4.4.1.1.2 Drop Hammers Drop (gravity) hammers shall not be used for concrete piles or for piles whose design load capacity exceeds 30 tons. When gravity hammers are permitted, the ram shall weigh not less than 2,
40、000 pounds and the height of drop shall not exceed 15 feet. In no case shall the ram weight of gravity hammers be less than the combined weight of the drive cap and pile. All gravity hammers shall be equipped with hammer guides to insure concentric impact on the dnve head or pile cushion. 4.4.1.1.3
41、Air Steam Hammers The weight of the striking part of aidsteam hammers used shall not be less than l/3 the weight of pile and drive cap, and in no case shall the striking part weigh less than 2,750 pounds. The plant and equipment furnished for aidsteam hammers shall have sufficient capacity to main-
42、tain, under working conditions, the pressure at the ham- mer specified by the manufacturer. 4.4.1.1.4 Diesel Hammers Open-end (single acting) diesel hammers shall be equipped with a device to permit the Engineer to deter- mine hammer stroke at all times during pile driving oper- ations. Closed-end (
43、double acting) diesel hammers shall 492 HIGHWAY BRIDGES 4.4.1.1.4 be equipped with a bounce chamber pressure gauge, in good working order, mounted near ground level so as to be easily read by the Engineer. A correlation chart of bounce chamber pressure and delivered hammer energy shall be provided b
44、y the Contractor. 4.4.1.1.5 Vibratory Hammers Vibratory or other pile driving methods may be used only when specifically allowed by the Special Provisions or in writing by the Engineer. Except when pile lengths have been determined from load test piles, the bearing capacity of piles driven with vibr
45、atory hammers shall be verified by redriving the first pile driven in each group of 1 O piles with an impact hammer of suitable energy to measure the pile capacity before driving the remaining piles in the group. 4.4.1.1.6 Additional Equipment or Methods In case the required penetration is not obtai
46、ned by the use of a hammer complying with the above minimum re- quirements, the Contractor may be required to provide a hammer of greater energy or, when permitted, resort to supplemental methods such as jetting or preboring. 4.4.1.2 Driving Appurtenances 4.4.1.2.1 Hammer Cushion All impact pile dri
47、ving equipment except gravity ham- mers shall be equipped with a suitable thickness of ham- mer cushion material to prevent damage to the hammer or pile and to insure uniform driving behavior. Hammer cush- ions shall be made of durable, manufactured materials, which will retain uniform properties du
48、ring driving. Wood, wire rope, and asbestos hammer cushions shall not be used. A striker plate shall be placed on the hammer cush- ion to insure uniform compression of the cushion material. The hammer cushion shall be inspected in the presence of the Engineer when beginning pile driving and after ea
49、ch 100 hours of pile driving. The hammer cushion shall be re- placed by the Contractor before driving is permitted to continue whenever there is a reduction of hammer cushion thickness exceeding 25% of the original thickness. 4.4.1.2.2 Pile Drive Head Piles driven with impact hammers shall be fitted with an adequate drive head to distribute the hammer blow to the pile head. The drive head shall be axially aligned with the hammer and the pile. The drive head shall be guided by the leads and not be free-swinging. The drive head shall fit around the pile head in such a manner as to pre- vent
