Pile driver
A pile driver is a device used to drive piles into soil to provide foundation support for buildings or other structures. The term is also used in reference to members of the construction crew that work with pile-driving rigs.
One type of pile driver uses a weight placed between guides so that it can slide vertically. It is placed above a pile. The weight is raised, which may involve the use of hydraulics, steam, diesel, or manual labour. When the weight reaches its highest point it is released, and hits the pile, driving it into the ground.
History
There are a number of claims to the invention of the pile driver. A mechanically sound drawing of a pile driver appeared as early as 1475 in Francesco di Giorgio Martini's treatise Trattato di Architectura. Also, several other prominent inventors — James Nasmyth, who invented a steam-powered pile driver in 1845, watchmaker James Valoué, Count Giovan Battista Gazzola, and Leonardo da Vinci — have all been credited with inventing the device. However, there is evidence that a comparable device was used in the construction of Crannogs at Oakbank and Loch Tay in Scotland as early as 5000 years ago. In 1801 John Rennie came up with a steam piledriver in Britain. Otis Tufts is credited with inventing the steam pile driver in the United States.Types
Ancient pile driving equipment used human or animal labor to lift weights, usually by means of pulleys, then dropping the weight onto the upper end of the pile. Modern piledriving equipment uses various methods to raise the weight and guide the pile.Diesel hammer
A modern diesel pile hammer is a large two-stroke diesel engine. The weight is the piston, and the apparatus which connects to the top of the pile is the cylinder. Piledriving is started by raising the weight; usually a cable from the crane holding the pile driver — This draws air into the cylinder. Diesel fuel is injected into the cylinder. The weight is dropped, using a quick-release. The weight of the piston compresses the air/fuel mixture, heating it to the ignition point of diesel fuel. The mixture ignites, transferring the energy of the falling weight to the pile head, and driving the weight up. The rising weight draws in fresh air, and the cycle continues until the fuel is depleted or is halted by the crew.From an army manual on pile driving hammers:
The initial start-up of the hammer requires that the piston be raised to a point where the trip automatically releases the piston, allowing it to fall. As the piston falls, it activates the fuel pump, which discharges a metered amount of fuel into the ball pan of the impact block. The falling piston blocks the exhaust ports, and compression of fuel trapped in the cylinder begins. The compressed air exerts a pre-load force to hold the impact block firmly against the drive cap and pile. At the bottom of the compression stroke, the piston strikes the impact block, atomizing the fuel and starting the pile on its downward movement. In the instant after the piston strikes, the atomized fuel ignites, and the resulting explosion exerts a greater force on the already moving pile, driving it further into the ground. The reaction of the explosion rebounding from the resistance of the pile drives the piston upward. As the piston rises, the exhaust ports open, releasing the exhaust gases to the atmosphere. After the piston stops its upward movement, it again falls by gravity to start another cycle.
Vertical travel lead systems
Vertical travel leads come in two main forms: spud and box lead types. Box leads are very common in the Southern United States and spud leads are common in the Northern United States, Canada and Europe.Hydraulic hammer
A hydraulic hammer is a modern type of piling hammer used instead of diesel and air hammers for driving steel pipe, precast concrete, and timber piles. Hydraulic hammers are more environmentally acceptable than older, less efficient hammers as they generate less noise and pollutants. In many cases the dominant noise is caused by the impact of the hammer on the pile, or the impacts between components of the hammer, so that the resulting noise level can be similar to diesel hammers.[Hydraulic press-in]
Specialty equipment which installs piles using hydraulic rams to press piles into the ground. This system is preferred where vibration is a concern. There are press attachments that can adapt to conventional pile driving rigs to press 2 pairs of sheet piles simultaneously. Other types of press equipment sit atop existing sheet piles and grip previously driven piles. This system allows for greater press-in and extraction force to be used since more reaction force is developed. The reaction-based machines operate at only 69 dB at 23 ft allowing for installation and extraction of piles in close proximity to sensitive areas where traditional methods may threaten the stability of existing structures.Such equipment and methods are specified in portions of the internal drainage system in the New Orleans area after Hurricane Katrina, as well as projects where noise, vibration and access are a concern.
Vibratory pile driver/extractor
Vibratory pile hammers contain a system of counter-rotating eccentric weights, powered by hydraulic motors, and designed so that horizontal vibrations cancel out, while vertical vibrations are transmitted into the pile. The pile driving machine positioned over the pile with an excavator or crane, and is fastened to the pile by a clamp and/or bolts. Vibratory hammers can drive or extract a pile. Extraction is commonly used to recover steel "H" piles used in temporary foundation shoring. Hydraulic fluid is supplied to the driver by a diesel engine-powered pump mounted in a trailer or van, and connected to the driver head via hoses. When the pile driver is connected to a dragline excavator, it is powered by the excavator's diesel engine. Vibratory pile drivers are often chosen to mitigate noise, as when the construction is near residences or office buildings, or when there is insufficient vertical clearance to permit use of a conventional pile hammer. Hammers are available with several different vibration rates, ranging from 1200 vibrations per minute to 2400 VPM. The vibration rate chosen is influenced by soil conditions and other factors, such as power requirements and equipment cost.Piling rig
A piling rig is a construction machine for piling in foundation engineering. It is mainly applied to drill in sandy soil, clay, silty clay, etc. and widely used cast-in-place piles, diaphragm walls, foundation reinforcement and other foundation projects. Its rated power of engine is around 108–450 kW, output torque 60–400 kN•m, maximum pile diameter 1.5–4 m, maximum pile depth 60–90 m. It can meet construction requirement of kinds of foundation engineering projects. It generally applies hydraulic crawler chassis, automatic lift box-type mast, telescopic drill pipe, auto vertical adjustor, depth indicator, etc. Its operation applies hydraulic pilot control, load sensor, thus is easy to control. Main and auxiliary hoisting can meet different requirements in construction sites. The rig can be used on piling construction in dry, wet soil and rock by equipping with drilling tool, and can be equipped with long screw drill, diaphragm wall grab, vibratory hammer, etc., to achieve many functions. It is mainly used in foundation engineering of municipal construction, expressway, bridge, industrial and civil buildings, diaphragm wall, water conservancy project, and slope protection.Piling rigs categories
- small-sized – torque is around 60–100 kN m, engine power 108 kW, drilling diameter 0.5–1.2 m, drilling depth 40 m, total quality 40 t.
- middle-sized – torque is around 120–180 kN m, engine power 125–200 kW, drilling diameter 0.8–1.8 m, drilling depth 60 m, total quality 42–65 t.
- large-sized - torque is around 240 kN m, engine power 300 kW, drilling diameter 1–2.5 m, drilling depth 80 m, total quality 100 t.
Environmental effects (offshore pile driving)