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Last edited 09 Sep 2026

Vibro hammer

1 Introduction
2 Related articles on Designing Buildings
3 External references

[edit] Introduction

A vibro hammer, also known as a vibratory hammer, vibratory pile driver or vibratory driver/extractor, is a type of piling equipment used to install and extract piles by transmitting cyclic vibration into the pile.

Unlike an impact hammer, which drives a pile by repeated blows, a vibro hammer uses pairs of rotating eccentric masses to generate an oscillating force. This vibration can temporarily reduce resistance at the pile-soil interface, allowing the pile to penetrate the ground during installation or to be withdrawn during extraction.

Vibro hammers are commonly used with:

They are particularly common in civil engineering, marine construction and foundation work where high production rates and the ability to install and recover temporary piles are required.

[edit] Principle of operation and soil response

The main vibrating component of a vibro hammer is generally referred to as the exciter or gearbox. It contains pairs of eccentric weights mounted on shafts that rotate in opposite directions at the same speed. This arrangement causes the horizontal force components to largely cancel each other while the vertical components combine, producing an oscillating force that is transferred through the hammer and clamp into the pile.

Once securely connected, the hammer and pile behave as a coupled vibrating system. The cyclic movement affects conditions at the pile-soil interface and can reduce the resistance to installation or extraction.

The effectiveness of vibratory piling depends on the interaction between a range of factors, including:

Operating frequency.
Eccentric moment.
Centrifugal force.
Vibrating mass.
Pile geometry and weight.
Soil properties.
Depth of penetration.
Groundwater conditions.

The nominal force rating of a vibro hammer alone does not therefore determine whether it is suitable for a particular project.

Vibratory pile driving is generally most effective in granular soils, where particles can rearrange around the oscillating pile. Loose and medium-dense sands often respond particularly well. Performance can become more dependent on project conditions in dense sands, gravel, silty soils, cohesive soils, stiff clay and ground containing cobbles or other obstructions.

The term liquefaction is sometimes used loosely to describe the temporary reduction in resistance around a vibrating pile. However, this should not be confused with earthquake-induced geotechnical liquefaction. A more general description is that vibration causes temporary changes in soil structure and pile-soil interface resistance.

In cohesive soils, the mechanism differs from that in clean granular soils, and penetration may depend more strongly on vibration amplitude, pile geometry and changes in interface resistance.

[edit] Performance parameters and main components

Important performance parameters include centrifugal force, eccentric moment, frequency and amplitude.

Centrifugal force is the dynamic force generated by the rotating eccentric masses. It generally increases with eccentric mass, eccentric radius and rotational speed. Higher centrifugal force can increase the ability of the system to overcome soil resistance, but it must be considered alongside the other characteristics of the hammer and pile.

Eccentric moment is related to the mass of the eccentric weights and their distance from the shaft centre. It influences the displacement amplitude of the vibrating system. As the total vibrating mass increases, a larger eccentric moment may be required to maintain adequate amplitude.

Frequency describes the number of vibration cycles produced over a given period and is commonly expressed in hertz or vibrations per minute. Suitable operating frequencies depend on factors such as pile type, soil conditions, vibration restrictions, carrier configuration and the required penetration rate.

Amplitude is the magnitude of the cyclic movement produced by the vibrating system. Frequency and amplitude should be considered together. A high-frequency hammer with insufficient amplitude may perform poorly on a heavy pile, while a hammer with suitable eccentric moment and amplitude may be more effective at a lower frequency.

A hydraulic vibro hammer system generally comprises the following components:

Exciter or gearbox: Contains eccentric shafts, bearings, synchronising gears, lubrication systems and structural housings. These components are subjected to continuous cyclic loading and require appropriate lubrication, bearing maintenance and alignment.
Hydraulic motors: Drive the eccentric shafts. Their performance depends on hydraulic pressure, oil flow, motor displacement and hydraulic efficiency.
Suppressor: Usually positioned between the vibrating unit and the supporting crane or carrier. It commonly incorporates elastomeric elements to reduce the vibration transmitted to the supporting equipment.
Clamp: Connects the hammer to the pile. Adequate clamping force is necessary to maintain effective force transfer and prevent slippage, which can reduce performance, damage the pile and create a handling hazard.
Hydraulic power unit: Large crane-suspended systems commonly use a separate hydraulic power pack to provide the required flow and pressure. Important considerations include oil flow, operating pressure, engine power, cooling capacity, filtration and the diameter and length of hydraulic hoses.

[edit] Types of vibro hammer

Vibro hammers can be mounted on different types of carrier according to the scale and requirements of the work.

[edit] Crane-suspended vibro hammers

Crane-suspended vibro hammers are generally used for larger piling operations. Typical applications include large sheet pile sections, steel pipe piles, casing, marine piling, bridge foundations, temporary cofferdams and pile extraction.

The hammer is suspended from a crane and may be connected to a separate hydraulic power unit. Crane capacity, boom geometry, hook height, suspended weight and lifting arrangements must be considered when selecting the equipment.

[edit] Excavator-mounted vibro hammers

Excavator-mounted vibro hammers connect directly to an excavator boom or attachment system. They are commonly used for sheet pile installation, trench support, utility works, temporary retaining walls, small cofferdams and projects with restricted access.

Many excavator-mounted systems use the host excavator's auxiliary hydraulic system. The excavator must therefore provide sufficient hydraulic flow and pressure, while also maintaining adequate cooling capacity and stability.

[edit] Side-grip vibro hammers

A side-grip vibro hammer grips a pile from the side rather than only from the top. This can allow an excavator to pick up, position, pitch, drive and extract piles without separate pile-handling equipment in some applications.

Side-grip systems can be particularly useful where overhead clearance is restricted. Their capacity remains dependent on factors including excavator size, pile length and weight, hydraulic capacity and ground conditions.

[edit] Fixed-moment and variable-moment systems

Vibro hammers can also be classified according to the way eccentric moment is controlled.

A fixed-moment hammer operates with a predetermined eccentric configuration. It accelerates to its operating speed while maintaining the same mechanical eccentric arrangement and is commonly used for general-purpose piling.

A variable-moment hammer can alter the eccentric moment during operation. The eccentric moment may be reduced during start-up and shutdown, helping to limit vibration while the hammer passes through lower operating frequencies. Such equipment may be considered where piling is undertaken close to existing buildings, sensitive structures, underground services, railways or sensitive equipment.

[edit] Piles and applications

Vibro hammers are commonly used to install and extract steel sheet piles. Sheet piles may be used for retaining walls, cofferdams, excavation support, marine bulkheads, seawalls, flood defences and temporary works. Vibratory installation can be effective in suitable soils, while other methods may be required where ground conditions prevent the pile from reaching the required depth.

Steel pipe piles and H-piles may also be installed using vibratory equipment where ground conditions and project requirements are suitable. Whether vibratory installation alone is appropriate for a permanent load-bearing pile depends on the foundation design and the specified method of pile acceptance.

Vibro hammers are also frequently used to install and extract steel casing for foundation works, excavation support and marine construction.

Typical applications include:

[edit] Vibro hammers and impact hammers

Vibro hammers and impact hammers have different operating characteristics and are not necessarily competing technologies.

Potential advantages of vibro hammers include rapid penetration in suitable ground, high productivity for sheet piling, continuous operation and the ability to extract piles. They also avoid the repeated high-amplitude impact events associated with impact hammers.

Impact hammers may be more suitable where dense layers must be penetrated, where specified driving criteria must be achieved, or where the installation process forms part of the assessment of pile performance.

On some projects, both methods may be used. A vibro hammer may initially install a pile through favourable upper soil layers, after which an impact hammer or another method is used to achieve the required penetration or satisfy the specified acceptance criteria.

Successful penetration to a specified depth using a vibro hammer does not, by itself, demonstrate the final load-bearing capacity of a permanent foundation pile. The method of pile acceptance should be determined by the project engineer and construction specification and may include static load testing, dynamic testing, instrumentation or other project-specific engineering assessment.

[edit] Selection and hydraulic system considerations

Vibro hammer selection should be based on the complete pile-soil-equipment system rather than on a single performance figure.

Information required for preliminary selection normally includes:

Pile type, profile and dimensions.
Pile weight and length.
Required embedment.
Ground profile.
Ground investigation information, including SPT or CPT data where available.
Groundwater conditions.
Installation or extraction requirements.
Crane or excavator details.
Environmental and access constraints.

Important equipment characteristics include:

Centrifugal force.
Eccentric moment.
Maximum operating frequency.
Amplitude.
Clamp force.
Extraction capacity.
Hydraulic pressure and oil flow.
Operating weight.

For hydraulic vibro hammers, the hammer and hydraulic power source must be considered as one system. Important factors include required oil flow, maximum operating pressure, return-line pressure, hose diameter and length, oil temperature, cooling capacity and hydraulic fluid specification. Excessively long or undersized hoses can increase hydraulic losses, while continuous vibratory operation can generate significant heat.

Clamp selection should also form part of the overall equipment selection process. Clamps may be designed for sheet piles, H-piles, pipe piles or casing. The clamp must be compatible with the pile section and provide adequate gripping force throughout installation and extraction.

[edit] Ground vibration, noise and environmental effects

Vibro hammers intentionally generate vibration and can transmit vibration through the ground. Although they may reduce the repeated impulsive effects associated with impact hammers, they can still affect nearby buildings, infrastructure and sensitive equipment.

Ground vibration is influenced by factors including hammer frequency, eccentric moment, soil stratification, groundwater conditions, pile type, distance from the source and the characteristics of nearby structures.

Projects close to sensitive buildings or infrastructure may require measures such as:

Pre-construction condition surveys.
Ground vibration monitoring.
Peak particle velocity monitoring.
Agreed trigger levels.
Stop-work limits.
Alternative installation methods.
Appropriate equipment selection.

Vibro hammers also produce mechanical and hydraulic noise, as well as noise from the crane or excavator and contact between equipment components. In marine applications, vibratory piling can generate underwater sound and vibration. Environmental requirements may therefore relate to noise, protected species, water quality and hydraulic fluid management.

The requirements applicable to a project should be identified during planning and should not be assumed to be satisfied solely by selecting a particular type of piling equipment.

[edit] Pile extraction

The ability to extract piles is an important application of vibratory equipment. During extraction, vibration can reduce resistance at the pile-soil interface while the crane, excavator or other extraction system applies an upward force.

Extraction performance is influenced by factors including: