Piles and Pile Driving Equipment

Anchor Pile

• A pile connected to a structure for lateral support or to resist uplift.

Butt of a Pile

• The larger end of a tapered pile, typically the upper end of a driven pile.

Cushion

• Material inserted between the ram of a pile hammer and the driving cap, and for concrete piles, between the driving cap and the pile.
• Provides uniform distribution of impact forces.
• Typical materials: micarta, steel, aluminum, coiled cable, and wood.

Cutoff

• The prescribed elevation at which the top of a driven pile is cut.
• Also, the portion of pile removed after driving.

Downdrag

• Negative friction of soil gripping a pile in settling soils, adding load to the pile.

Driving Cap or Helmet

• A steel cap placed over the pile butt to prevent damage during driving.
• Shaped to fit a specific pile and cushion.

Embedment

• The length of pile from the ground surface or cutoff to the tip of the pile.

Overdriving

• Driving a pile in a manner that damages the pile material, often due to continued hammering after refusal.

Penetration

• Gross penetration: Downward axial movement of the pile per hammer blow.
• Net penetration: Gross penetration less the rebound (net downward movement).

Pile Bent

• Two or more piles driven in a group and fastened together by a cap or bracing.

Pile-Driving Shoe

• A metal shoe placed on the pile tip to prevent damage and improve driving penetration.

Pile Tip

• The lower end of the pile, usually the smaller end for timber piles.

Soldier Pile

• An H or wide flange member driven at intervals with horizontal lagging to support excavation walls.

Tension Pile

• A pile designed to resist uplift.

Classification of Piles by Use

• Sheet Piles:
  • Used to create a rigid barrier for earth and water.
  • Applications: cutoff walls under dams, cofferdams, bulkheads, and trenching.
  • Materials: steel, prestressed concrete, timber, or composite.
• Load Bearing Piles:
  • Timber:
    • Treated with preservative
    • Untreated
  • Concrete:
    • Precast-prestressed
    • Cast-in-place with shells
    • Augured cast-in-place
  • Steel:
    • H-section
    • Steel pipe
  • Composite: Concrete and steel, plastic with steel pipe core

Pile Information by Type

• Wood:
  • Typical capacity: 15 - 60 tons
  • Typical lengths: 10 - 45 ft
  • Cost range: 8 - $15 per linear ft
• Concrete:
  • Typical capacity: 60 - 120 tons
  • Typical lengths: 30 - 60 ft
  • Cost range: 10 - $15 per linear ft
• Steel Pipe (closed end):
  • Typical capacity: 60 - 150 tons
  • Typical lengths: 30 - 90 ft
  • Cost range: 16 - $22 per linear ft
• Composite:
  • Typical capacity: 60 - 150+ tons
  • Typical lengths: 60 - 200 ft
  • Cost range: 18 - $30 per linear ft

Timber Piles

• Made from tree trunks, available worldwide.
• Ordinary lengths: 15 to 45 ft.
• Pine piles: up to 80 ft.
• Douglas fir piles: > 100 ft (Pacific Northwest).
• Typical design loads: 10 to 60 tons.

Treated Timber Piles

• Long service life if permanently wet (below the water table).
• Liable to decay when exposed to fluctuating water table.
• Preservative treatments: salt or creosote to reduce decay and fight marine borers.
  • American Wood Preservers' Association (AWPA) requires 20 pounds per cubic foot creosote in timbers used in marine waters.
  • Preservatives and techniques should be carefully selected as they may have environmentally detrimental effects.
  • The Environmental Protection Agency has approved creosote-treated timber piling and timbers for marine water applications.
  • Treated piling lasts for 50 years in northern marine waters and 20 years in southern waters.

Untreated Timber Piles

• Limited lifespan if exposed to the elements without treatment.
• ASTM D25-99: Standard specification for Round Timber Piles.
• Straightness check: A straight line from the center of the butt to the center of the tip shall lie entirely within the body of the pile.
• Free from short crooks that deviate by more than 2.5 in. from straightness in any 5-ft length.

Concrete Piles

• May be precast or cast-in-place.
• Precast piles are manufactured in established plants and are either prestressed or post-tensioned. They come in square, cylindrical, or octagonal shapes.
• Precast-Prestressed Concrete piles manufacturers at established plants conform to the Prestressed Concrete Institute Manual for Quality Control.
• Manufactures piles (specially with large orders), transportation costs may be significant. Therefore, it may be cost-effective to set up a casting facility on the job site or within the vicinity.
• Square and octagonal piles are cast in horizontal forms on casting beds, whereas cylinder piles are cast on cylindrical forms and then centrifugally spun.
• Hollow concrete cylinder pile sections, with a group of solid concrete square piles.
• After the piles are cast, they are normally steam cured until they have reached sufficient strength to allow them to be removed from the forms.
• Under controlled curing conditions and utilizing concrete with 5000psi or greater, the piles can be removed from the forms in as little as 24 hours, or as soon as the concrete has developed a compressive strength of 3500 psi.
• The piles are then stored and allowed to cure for 21 days or more before reaching the driving strengths.
• Piling for marine applications may require that the spirals be epoxy coated.
• Square and Octagonal piles are traditionally cast on beds 200 to 600 ft long so multiple piles can be cast and prestressed simultaneously.
• Cylinder piles are cast in short ections of up to 16 ft in length with prestressing sleeves or ducts cast into the wall of the pile.
• Typical outside diameters (OD) are 36, 42, 48, 54, and 66inches with wall thickness varying from 5in to 6in, depending on the design properties of the pile.
• Once the concrete is placed in the form, the concrete and the form are centrifugally spun, causing the concrete to consolidate. After sections have been steam cured and the concrete has obtained sufficient strength, the sections are assembled to the proper pile length.
• The prestressing strand is pulled through the sleeves or ducts and then tensioned with jacks. Finally, the tensioned strands are pressure grouted in the sleeves.
• The precast-prestressed piles canbe transported by truck to land-based projects or they can be moved by barge in the case of marine projects.
• Concrete piles must be handled with care to prevent breakage or damage due to flexural stresses. Long piles should be picked-up at several points to reduce the unsupported lengths.

Driving Concrete Piles

• A driven pile must remain structurally intact and not be stressed to its structural limits during its service life or driving.
• Pile damage often occurs due to excessive stress levels during driving.
• Control of driving stress is a critical pile driving requirement.

Cast-in-Place Concrete Piles

• Constructed by placing concrete into a tapered or cylindrical hole previously driven into the ground or into a hole in the ground from ehich a drivenmandrel (steel core) has been withdrawn.
• The cast-in-place displacement-type pile can be of two forms.

1. Involves driving a temporary steel tube with a closed end into the ground to form a void in the soil, which is then filled with concrete as the tube is withdrawn.
2. Same as 1 except the steel tube is left in place to form a permanent casing.

• There are also driven cast-in-situ concrete piles where casing, closed at the bottom with a plug or dry concrete or gravel or with anshoe, is driven into the ground to the required depth. Concrete is then placed into the casing.
• There are also nondisplacement cast-in-place piles where the soil is removed and the resulting hole is filled with concrete. One form of which is augured cast-in-place pile (ACIP).
• These piles are constructed by rotating a hollow-shaft continuous flight auger into the soil to a predetermined tip elevation or refusal, whichever occurs first. When the desired depth is reached, a high-strength grout is injected under pressure through the hollow shaft. The auger is withdrawn in a controlled manner, as grout pumping continuous.

Steel Piles

• In constructing foundations that require piles driven to great depths, steel pipes probably are more suitable than any other type.
• They are more costly than concrete piles, but they have a high load-carrying capacity which can reduce the driving cost.

Steel H Section Piles

• They are used as point-bearing piles with typical lengths of 60 to 200 ft.
• H piles can be susceptible to deflection on striking boulders, obstructions, or an inclined rock surface.
• Steel H piles can be driven is short lengths, and additional lengths are then welded on top of the previously driven section. This is advantageous when there is heigh restrictions.

Steel Pipe Piles

• Pipe piles are most efficient as friction piles as they have substantial surface area that interacts with the surrounding soil to provide significant frictional load resistance.

Composite Piles

• These are developed and offered to meet the demands of special situations.

Concrete-Steel Composite Piles

• With extremely hard soils or soil layers, it may be cost effective to use a composite concrete and steel pile.
• The top porion of the pile is a prestressed concrete pile, and the tip is a steel H pile embedded into the end of the concrete pile.
• This composite design is suggested for marine applications, where the concrete pile section offers resistance to deterioration and the steel pile tip enables penetration for hard driving conditions.

Steel-Conrete Composite Piles

• These type comprises a steel casing witha hollow spun concrete core, resting on a solid driving shoe.
• It combines the advantages of a high-quality concrete core with the high tensile strength of the external steel casing.
• These piles can provide higher durability and improved drivability.

Plastic with Steel Pipe Core Piles

• These piles are immune to marie borer attacks, eliminating the need for creosote treatments or special sheathings in marine environments.

Sheet Piles

• Are used primarily to retain or support earth.
• They are commonly used for bulkheads and cofferdams and when excavation depths or soil conditions require temporary or permanent bracing to support the lateral loads imposed by the soil or by the soil and adjacent structures.

Timber Sheet Piles

• Where supported loads are minimal, timber sheet piles can be used.
• Three rows of equal-width planking are nailed and bolted together so that the two outer planks form the groove and the middle plank forms the tongue.
• The timbers are driven with a light hammer or jetted into place.
• Timber wales may be used to add support to the system.

Prestressed Concrete Sheet Piles

• Concrete sheet piles are the best suited for applications where corrosion is a concern, such as marine bulkheads.
• The prestressed concrete sheets are precast in thickness ranging from 6 to 24in and usually have width of 3 to 4 ft.
• Conventional steam, air, or diesel hammers can be used to drive concrete sheet piles. However, jetting is often required to attain the proper tip elevation.

Steel Sheet Piles

• This sheet pile is a rolled section that is interlocked with adjacent sections to form a continuous wall.
• The hot rolling process includes the formation of a geometrically definedinterlock.
• Most steel sheet piles are supplied in standard ASTM 328 grade steel, but high-strength low-alloy grades ASTM A572 and ASTM A690 are available for use where larger loads must be supported or where corrosion is concerned.
• For marine applications, epoxy coated pilse can be used.
• Sheet piles are driven individually or in pairs, frequently with the use of vibratory hammer and a guide frame or template.
• When a vibratory hammer is used, the vibrator should be brought to speed before beginning the driving similarly, when extraction, it is oftenbest to drive the pile a little first, to break the static friction.

Pile Hammers

• Variable surface conditions can dictate the use of different pile hammers.
• Pile hammer furishes the energy required to drive a pile. It is designated by tyoe and size.

1. Drop
2. Single-acting steam or compressed air
3. Double-acting steam or compressed air
4. Differential-acting steam or compressed air
5. Diesel
6. Hydraulic-impact and drivers
7. Vibratory drivers

Factors to be considered when selecting a method of driving piles:

• size and the weight of the pile
• driving resistance that has to be overcome to achieve the required penetration
• available space and headroom for equipment
• noise restrictions

1. Drop Hammers

• It is a heavy metal wight that is lifted by a hoist line then released and allowed to fall onto the top of the pile.
• The hammer may be released by a trip and fall freely, or it may be released by loosening the friction band on the hoisting drum and permitting the weight of the hammer to unwind the rope from the drum.

2. Single-Acting Hammers

• A single-acting steam hammer has a freely falling weight, called a "ram," that is lifted by steam or compressed air, whose pressure is applied to the underside of a piston that is connected to the ram through a piston rod.
• When the piston reaches the top of the stroke, the steam or air pressure is released and the ram falls freely to strike the rop of the pile.

3. Double-Acting Hammers

• With double-acting hammers, the striking ram (piston) is driven by comressed air or steam when both rising and falling.
• The air or steam enters a valve box containing a slide valve that sends it alternately to each side of the piston, while the opposite side is connected to the exhaust ports.
• commonly delivery 95-300 blows per minute its ram may be advantageous when driving light-medium weight piles

4. Differential-Acting Hammers

• It is a modified single-acting hammer in that the air or steam pressure used to lift the ram is not exhausted at the end of the upward stroke but is valved over the piston to accelarate the ram on the downstroke.
• it has both the advantage of single- and double-acting hammer require the use of a pile cap with cushioning material and a set of leads will drive a pile in one-half the time required by the same- size single-acting hammer and doing so, will use 25%-35% less air or steam

5. Diesel Hammers

• Is a self-contained driving unit that does not require an external source of energy such as an air compressor or steam boiler.
• simpler and more easily moved from one location to another a complete unit: piston or ram, an anvil, fuel-oil tanks, a fuel pump, injectors, and a mechanical lubricator
• After a hammer is placed on top of a pile, the combined piston and ram are lifted to the upper end of the stroke and released to start the unit operating.

6. Hydraulic Impact Hammers

• They are reported to have an efficiency of 90% or better in delivering energy to the pile.
  • Hydraulic Drop Hammer. With some hammers, the ram is lifted by hydraulic pressure to a preset height and allowed to free-fall onto the anvil. The height of the drop can be varied to match the pile and ground conditions.
  • Double-Acting Hydraulic Hammer. The ram, which is lifted by hydraulic pressure on a double-acting hydraulic hammer, is also driven hydraulically on its downward stroke. The net energy applied to the pile by the accelerated ram is measured during every blow on a control panel and can be continuously reg-ulated. These hammers can deliver 50 to 60 blows per minute.
  • Hydraulic Drivers Press-in hydraulic pile drivers, which can be used for thrusting and extracting steel H piles and steel sheet piles, incorporates a gripping and pushing or pulling technique. This pile driver grips the pile and then pushes the pile down approximately 3 ft. At the end of the downstroke, the pile is released and the gripper slides up the pile 3 ft to begin the process of another push. can be used in reverse for extracting piles develop up to 140 tons of pressing or extracting force, are compact, make minimal noise, and cause lite vibration. well suited for driving piles in areas where there is restricted overhead space

7. Vibratory Drivers

• They are specially effective when the piles are driven into water-saturated noncohesive soils.
• The drivers may experience difficulty in driving piles into dry sand, or similar materials, or into cohesive soils that do not respond to the vibrations.
• The drivers are equipped with horizontal shafts, to which eccentric weights are attached. As the shafts rotate in pairs, in opposing directions and at speeds that can be varied in excess of 1,000 rpm, the forces produced by the rotating weights produce vibrations.
• The vibrations are transmitted to the pile because it is rigidly connected to the driver by clamps. From the pile, the vibrations are transmitted into the adjacent soil. The agitation of the soil materially reduces the skin friction between the soil and the pile. This is especially ire when the soil is saturated with water. The combined dead weight of the pile and the driver resting on the pile will drive the pile rapidly.