CLASSIFICATION OF PILES Piles can be classified on the basis of either their use or the materials from which they are made. On the basis of use, there are two major classifications: (1) sheet and (2) load bearing.
SHEET PILES Sheet piles are used primarily to create a rigid barrier for earth and water. Typical uses include cutoff walls under dams, and for cofferdams, bulkheads, and trenching.
PILE TYPES Timber Treated with a preservative Untreated Concrete Precast-prestressed Cast-in-place with shells Augered cast-in-place
PILE TYPES Steel H section Steel pipe Composite Concrete and steel Plastic with steel pipe core
TIMBER PILES Timber piles are made from the trunks of trees. Such piles are available in most sections of the country and the world. Ordinary lengths are 15 to 45 ft.
Concrete piles may be either precast or cast-in-place. CONCRETE PILES
STEEL PILES Load-bearing steel piles can be H - sections, hollow box or tubular sections, or pipes.
COMPOSITE PILES Several types of composite piles are available. These are usually developed and offered to meet the demands of special situations. Two of the most common situations that cause problems, when conventional piles are used, are hard driving conditions and warm marine environments.
DRIVING PILES Crawler crane w/single acting air hammer and hydraulic leads. Driving 12-in. concrete piles.
DRIVING PILES The forces that enable a pile to support a load also cause the pile to resist the efforts made to drive it. The total resistance of a pile to penetration will equal the sum of the forces produced by skin friction and end bearing.
DRIVING PILES Depending on the size of the project, one or more of the test piles would be selected for load testing.
LOAD TEST Reaction frame and hydraulic jacks used to load test a 54-in. concrete cylinder pile.
PILE HAMMERS Variable subsurface conditions can dictate the use of different pile hammers. The function of a pile hammer is to furnish the energy required to drive a pile.
PILE HAMMERS 1.Drop 2.Single-acting steam or compressed air 3.Double-acting steam or compressed air 4.Differential-acting steam or compressed air
DROP HAMMERS A drop hammer is a heavy metal weight that is lifted by a hoist line, then released and allowed to fall onto the top of the pile. Because of the high dynamic forces, a pile cap is positioned between the hammer and the pile head.
SINGLE-ACTING HAMMERS These hammers rely solely on gravity acting on the striking weight to achieve their driving energy. The a freely falling weight, called a “ram,” that is lifted by steam or compressed air.
DOUBLE-ACTING HAMMERS With double-acting hammers, the striking ram is driven by compressed air or steam both when rising and when falling. Thus, with a given weight of ram, it is possible to attain a desired amount of energy per blow with a shorter stroke than with a longer single- acting hammer.
DIFFERENTIAL- ACTING HAMMERS A differential-acting air 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 accelerate the ram on the downstroke.
DIESEL HAMMERS A diesel pile ‑ driving hammer is a self- contained driving unit that does not require an external source of energy such as an air compressor or steam boiler.
DIESEL HAMMERS The downstroke of the ram compresses air and fuel to ignition heat and the resulting explosion drives the pile downward and the ram upward to repeat its stroke.
DIESEL HAMMERS Diesel hammers impart compression, impact and explosion energy to the pile.
DIESEL HAMMERS 1. Raise the piston to start. 2. Injection of diesel fuel and compression. 3. Impact and explosion. 1 2 3
DIESEL HAMMERS 4. Exhaust ports exposed and gases escape. 5. Draws fresh air through the exhaust ports. 4 5
DIESEL HAMMERS Fuel usage varies with the size of the hammer see Table 19.4. DELMAG 10,500 ft-lb0.7 gal/hr 58,248 ft-lb2.11 gal/hr 107,177 ft-lb4.23 gal/hr 300,000 ft-lb7.93 gal/hr
HYDRAULIC IMPACT HAMMERS There is a trend toward the use of hydraulic hammers. A hydraulic hammer operates on the differential pressure of hydraulic fluid instead of compressed air or steam.
POSITIONING PILES DURING DRIVING When driving piles, it is necessary to have a method that will position the pile in the proper location with the required alignment or batter and that will support the pile during driving.
POSITIONING PILES DURING DRIVING Fixed leads have a pivot point at the crane’s boom top and a brace at their bottom that attaches to the crane. Fixed leads offer good control of the pile position and keep the pile in correct alignment with the hammer so that eccentric impacts are minimized.
POSITIONING PILES DURING DRIVING Leads that are not attached at their bottom to the crane or driving platform are known as “swing leads.” The leads and hammer are usually held by separate lines from the crane.
SWING LEADS Steam hammer used to drive 54-in. concrete cylinder piles, with swing leads.
PILE LEADS Stabbing points at the end of a set of leads.
POSITIONING PILES DURING DRIVING Many times a template is used to support and hold the pile in the proper position during driving. Templates are usually constructed from steel pipe or beams and may have several levels of framing to support long piles or piles on a batter.
TEMPLATE Floating rig driving concrete piles using a template.
TEMPLATE Three 8 ft diameter steel cylinder piles standing in the template on a batter ready for driving.
HANDLING PILES Care must be exercised to prevent damage to the pile from flexural stresses.
POINTERS For concrete piles the weight of the hammer ram should be one third the pile weight. Easy to start a pile with an air hammer. Diesel hammers will not start when the pile is in soft material.
POINTERS Position the crane so it can reach the driving position and the piles with out traveling.
POINTERS Driving time: 45 to 50 ft piles normally can be driven in 5 - 10 min. But in hard material it can take 4 hr.