450-1 DESCRIPTION
Bearing piles are used to support structures where dependable foundation materials are so far below the ground surface that spread footings are not economical. They transfer loads from the structure to the bearing material through skin friction, point bearing, or a combination of both.
Piles may be timber, steel, or concrete as indicated in the plans.
450-3 CONSTRUCTION METHODS
(B) PILE INSTALLATION
Piles should be driven to the accuracy shown in this specification. Pushing, pulling, bracing, or bending piles is not allowable to meet the accuracy requirements. It is highly recommended that the contractor use a rigid template when installing piles.
Preparation is very important in pile driving. A little extra time spent in preparation will ensure a proper pile installation.
The position of every pile is shown on the plans. Each pile should be located in correct position and is to be vertical or battered as specified. Flanges of steel H-piles are to be oriented as shown on the plans. The Contractor is responsible for pile layout and the Technician is responsible for checking the layout independently before pile driving is started.
Alignment of each pile should be checked before driving starts. Vertical piles can be checked in the leads with a plumb bob or carpenter's level. Battered piles can be checked in the leads using a triangular template, cut to the correct batter and a carpenter's level.
Certified welders will be required for welding points and splices on steel piles. When splicing steel piles, the welded butt splice details are shown on the plans. As an alternate, the Contractor may request to splice steel piles with an approved splicer.
Contractors are allowed to place a hole in steel piles for safe lifting purposes. Holes are not allowed to be used for supporting falsework or for any other reasons unless approved by the Engineer. The size of the hole is limited to a one and one-half (1½) inch diameter if the hole is allowed to remain in place and must have an edge distance of at least one hole diameter. If the hole is formed with a cutting torch, the portion of the pile above the bottom of the hole must be cut off and wasted. Burned holes cannot remain in place or be repaired.
For H-Piles, with a drilled or punched hole, no repair is necessary other than touch up of any applicable coating in accordance with Article 1076-7.
For Pipe Piles, with a drilled or punched hole, the following criteria shall apply:
- If the location of the hole is within the limits of required galvanization or metallization as shown on the plans, the portion of the pile above the bottom of the hole must be cut off and wasted.
- As an exception, if the hole is completely encased in concrete from the footing or cap, the hole may remain, and the coating repaired in accordance with Article 1076-7.
- For Closed End Pipe Piles, the portion of the pile above the bottom of the hole must be cut off and wasted regardless of the location, unless fully encased in concrete.
Holes shall not be located on the spiral weld of the pipe pile.
(D) DRIVEN PILES
In order to prevent possible damage to concrete in the vicinity of pile driving operations from vibration or shock waves, piles are not to be driven within
50 feet of concrete having an age of less than
3 curing days unless otherwise approved by the Area Construction Engineer. There may be some types of soil or subsurface conditions where the
50 foot limitation should be increased. The Area Construction Engineer should be consulted when the need for deviating from the standard requirement is being considered.
Augers, churn drills, or spudding may sometimes be necessary to attain the required penetration. The augered or drilled hole shall not be larger than the diameter or largest cross-sectional dimension of the pile to be driven.
Piles are generally driven to bearing by drop, steam, air or diesel hammers. Drop hammers may be used only when permitted by the State Construction Engineer. The Contractor may request to use a vibratory hammer to begin the driving operations. This request should be forwarded to the
Geotechnical Unit for approval along with other required driving methods and equipment. Pile driving equipment should be adequate to drive the size and length piles required without causing damage to the piles. Heavier piles require pile hammers with higher energy ratings. Before pile driving is started, the Resident Engineer shall check to be certain that the pile hammer has been approved for use in accordance with
Article 450-3(D)2 of the Specifications. Specifications for the pile hammer, cap block, and cushioning material are to be submitted to the Geotechnical Unit for review and approval. The data is to be submitted by the Contractor on the form contained on the
Geotechnical Unit web page.
A pile driving memorandum will be furnished to the Resident Engineer by the Geotechnical Engineering Unit. The memorandum will provide specific information for the proposed pile hammer or hammers for specific foundation locations. Maximum and minimum penetration rates for
10 blows will be provided. Piles should be driven within these limits. Do not add any safety factors to these values. Do not drive piles to refusal unless the memorandum so directs. All necessary safety factors will be included by the Geotechnical Engineering Unit.
Pay Record Book entries should not indicate an actual bearing value. The entry should indicate the required minimum blow count was achieved.
The Resident Engineer or his Technician shall inspect the equipment that the Contractor proposes to use prior to beginning pile driving operations to assure it is the same as was approved. Equipment shall be so designed and constructed that it will prevent lateral motion of the hammer and will support the pile during driving operations so that neither bending nor torsional stresses will be induced in the pile. If it is found during the driving operations that undesirable stresses or other damage is occurring, the Resident Engineer shall require the Contractor to stop his operations and obtain satisfactory equipment.
Steam, air, and diesel hammers are rated for energy at a specific speed. Check the blows per minute often to be sure they are operating at full capacity. All single acting hammers shall be equipped with a scale, or "jump stick" to determine the stroke. All double-acting hammers shall have a calibrated bounce chamber pressure gauge.
To utilize skin friction in the determination of bearing capacity, pile driving may be stopped and the piles allowed to sit undisturbed for a period of time. Minimum tip elevation, when required or minimum penetration into natural ground must be achieved prior to stopping driving operations. When pile driving operations are stopped prior to achieving the required bearing capacity, the piles must have a restrike or redrive to verify bearing. When the driving has been stopped by the Contractor to avoid driving more pile or having to splice additional length onto the pile, no payment will be made for the restrike. When the driving has been stopped at the direction of the Department, payment for the restrike will be made under
Article 450-3(D)4.
(F) PILE DRIVING ANALYZER
450-4 MEASUREMENT AND PAYMENT
Once the required bearing and penetration has been achieved, the Contractor shall stop driving the pile. If the amount of pile above the cutoff elevation exceeds
5 feet, then the Contractor shall cut the pile off at cutoff elevation and no payment will be made for cutting the pile or for the cutoff portion.
However, if the amount of pile above the cutoff elevation is
5 feet or less, then the Contractor may drive the remaining portion of the pile to grade in lieu of cutting off the pile, provided the remaining portion of the pile can be driven without damaging the pile or reaching the maximum blow count or practical refusal. When this occurs the additional length of pile driven will be measured and paid as described in this section.
