- AUGUST 2000

The NTU-PWD Geotechnical Research Centre and ICE Far East Pte Ltd co-organised a seminar titled Vibratory Driving : Sustainable Approach to Pile Design. The speaker, Mr Jan Kenkhuis has sixteen years of experience as geotechnical engineer/manager in offshore and near-shore site investigation and development projects.

The seminar introduced vibration technology and its applications in the foundation industry. Vibratory driving is based on the principle that the soil surrounding the pile temporarily liquefies due to vibrations during driving. Therefore, the piles are able to penetrate the soil under its own weight. There are many benefits of vibration technology.

Vibration technology makes it simpler, faster and more economical to install and use than conventional pile driving systems. There is relatively low noise; it is environmentally friendly; there is less risk of damage to nearby structures (especially with Resonance Free vibratory hammers); it can be used for extracting temporary piles; there is increased versatility and utilisation degree of hydraulic excavators (Excavator Mounted vibratory hammers); and it can be used underwater for off-shore pile driving.

At the seminar, the stages in a foundation development project was explored, namely, the design process, the pile installation process and the pile acceptance process. A brief explanation on the drivability study for vibratory driving was then presented together with the influence factors on vibratory driving.

The essential components of the vibratory hammers were then examined. Last but not least, new solutions such as Vibratory Driving Clamp (VDC), Resonance Free Vibratory Hammers and Excavator Mounted Vibratory Hammers were introduced.

Pile Driving with Vibratory Hammers

Generating vibrations in the objects to be driven, for example a sheet pile or tubular pile, causes the ground immediately adjacent to the moving surface to produce a temporary, and rapidly diminishing soil resistance. When the soil is vibrated, all particles within it move apart rapidly and randomly. Due to the reduced skin friction and ingress if water (in most cases), these particles then have much less resistance to an object being pushed through them.

As a consequence, relatively low forces are required to insert the object into or withdraw from the ground.

If the vibrations are stopped, the soil returns to its former load bearing condition; therefore the object can transfer high loads to the substrata, without the risk of deformation. Due to the fact that the impact force of a vibratory hammer is low in relation to that of a conventional impact hammer and the reduced resistance created by the vibrations, the vibratory hammer is eminently suitable for driving or withdrawing piles or profiles, in applications requiring little soil displacement.

Examples may include sheet-piles, H-profiles, open tubular piles, etc. Further specific areas of application for vibratory hammers are such as surface compaction and deep compaction.

The advantage of vibratory hammers include low impact force that ensure little or no damage or deformation to the pile, rapid driving, less noise and smaller and lighter equipment.

This environment friendly hammer can be used to withdraw piles already driven into the ground, which would otherwise remain in the ground forever.

Vibratory Driving Clamp (VDC^®)

The VDC^® clamp in conjuction with a vibratory hammer is one of the most innovative solutions for the installation of tubular piles. It has potential to cut the piling time by more than 30% because when using this pile installation method, the on-site splicing, cutting, and welding off main sections and add-ons will be obselete.

ICE has on-going research and development on vibration technology to improve on its products and services.