Pile Driver

Overview

A pile driver installs deep foundation elements by repeatedly striking the head of a pile until it reaches the design depth or refusal. The machine described here is a crawler-mounted rig with a diesel impact hammer running on a tall vertical guide called the leader. It is the workhorse of bridge foundations, port and marine works, high-rise foundations, and any site where soft surface soils must be bypassed to reach competent bearing strata.

The complete machine has three load paths working at once. The driving energy path runs from the Pile Driver Hammer through the driving cap into the pile. The structural reaction path carries the recoil and the weight of the suspended hammer down the Leader Mast into the Base Machine. The handling path uses the Winch System to raise the hammer between blows and to pitch each new pile into position. A single experienced crew can drive 10 to 30 piles per shift depending on pile length and ground conditions.

Diesel Impact Hammer

The heart of the rig is a single-acting diesel hammer. The Hammer Ram is a forged steel piston, between 2 and 8 tonnes depending on the model, that free-falls inside the Hammer Cylinder. Near the bottom of its stroke the ram covers the exhaust ports and compresses the trapped air. The Fuel Metering Pump injects a metered diesel charge, which atomises against the hot Anvil Block face and ignites at impact. The explosion drives the pile down and throws the ram back up for the next cycle, so once started the hammer runs on its own without external power.

Each blow delivers between 40 and 220 kJ. That energy reaches the pile through the Anvil Block, the Driving Cap (Helmet), and a sacrificial Pile Cushion. The cushion is a stack of plywood or plastic sheets that softens and lengthens the impact pulse. Without it, the sharp blow needed to advance the pile would crack a concrete pile head or split the timber. The cushion is replaced every few piles as it crushes and chars. The hammer is started by the Trip & Lift Mechanism, a hook that lifts the ram for the first blow and then releases it; the diesel cycle is self-sustaining from the second blow onward.

Leader and Guidance

The Leader Mast is a box-section mast assembled from bolted Mast Box Section modules, giving heights from 18 to 36 m. It does three jobs. It keeps the hammer and pile exactly in line through the Hammer Guide Rail rails so the blow lands square. It holds the pile during pitching and driving through the Pile Gate & Clamp, a hydraulic clamp with serrated Gate Jaw inserts that suit square, round, or H-section piles. And it sets the pile angle: the Batter Pivot Hinge at the mast foot lets the operator rake the leader up to 18 degrees forward or back for batter piles, which resist horizontal loads on wharves and abutments. The Mast Cap Sheave Block at the top carries the hoist sheaves that turn the winch ropes down to the hammer and the pile.

Base Machine and Powerpack

The whole rig rides on the Base Machine, a tracked carrier built like a crawler crane. Two Crawler Track assemblies, each with a sealed track chain, lower rollers, and a hydraulic Travel Motor, spread the 60 to 120 tonne operating weight and let the machine tram between pile positions. The upper structure rotates a full 360 degrees on the Slew Bearing, a large-diameter ball slewing ring driven by the Slew Drive. A bolt-on Counterweight balances the forward leader and hammer loads.

The Diesel Powerpack is a six-cylinder turbocharged diesel of 150 to 300 kW driving two variable-displacement Main Hydraulic Pump units. These supply both the implement and travel circuits at 320 to 350 bar. The Diesel Engine uses a common-rail fuel system with a Turbocharger for boost, and a combined Cooling Pack handles engine coolant, hydraulic oil, and charge air through a single hydraulically driven fan.

Hydraulics and Winches

The Hydraulic System does everything except the driving itself. The Leader Erection Cylinder pair raises the leader from its transport position to vertical, the Batter Cylinder units set and hold the rake, and the Control Valve Bank bank routes proportional flow to each function from the Hydraulic Tank.

Lifting is handled by the Winch System. The Main Hoist Winch is a hydraulic free-fall winch that raises the hammer between blows and lifts heavy piles. It carries a grooved Winch Drum, a planetary Winch Motor, and a spring-applied Winch Brake that holds the load whenever the motor is idle. A smaller Auxiliary Winch pitches each new pile, threading it through the gate and standing it under the hammer. Both run Wire Rope of 22 mm galvanised 6x36 construction.

Operator Cabin and Instrumentation

The Control Cabin is a falling-object-rated enclosure with a suspension Seat Assembly, proportional Joystick Controller controls, and a touchscreen Operator Display for engine and hydraulic data. The most important instrument is the Pile-Driving Analyzer, the pile-driving analyzer. It records the blow count, the set per blow, the measured pile-head force, and the driving stress. Engineers use these numbers to confirm that the pile has reached its design capacity, since the resistance felt at the hammer is a direct measure of how hard the ground is gripping the pile. Driving stops at a target set, for example 25 mm of advance for the last 10 blows, rather than at a fixed depth.

Electrical, Materials, and Variants

The Electrical System system runs at 24 V from a series battery pair charged by a belt-driven Alternator. The Wiring Harness ties the cab, powerpack, and sensors together, and the Machine Controller coordinates the engine, hydraulics, and the driving sequence.

Materials are chosen for shock and abrasion. The ram, anvil, and helmet are forged alloy steel through-hardened at the striking faces. Mast sections are welded structural steel, often weathering grade for marine work. Track components run sealed and lubricated against grit. Several variants exist on the same base machine: a vibratory hammer for sheet piles and sandy ground, a hydraulic hammer for low-noise urban sites, and a leader-mounted drilling mast for cast-in-place bored piles. The diesel impact rig described here remains the most common choice for driven precast and steel piles because of its high energy per blow and its ability to run without a separate power source once the hammer is started.