When large diameter piles, tubes or tunnel sections have to be installed horizontally over an apperiable distance, powerful tools are required to deliver the amount of driving energy, or of a sufficient cutting capacity.
IHC Hydrohammer B.V. is specialized in piling jobs where large diameter piles (up to 4,3m, 15ft diameter) have to be driven.
Due to two unique features in the design of the hydraulic driven, double acting Hydrohammer, it is possible to operate the hammers under every inclination, even horizontally.
- The first feature is the double acting principle of the hammer, whereby part of the kinetic energy of the ram is obtained by a pressurized gasbuffer above the main piston. When operating under a batter, increasing the pressure of the gasbuffer can compensate the loss of energy delivered by gravity.
- The ram of het Hydrohammer is guided by two oil-lubricated bearings. There is no contact between ram and guide columns of ram and housing. This prevents excessive wear and tear.
Principle of horizontal driving operation
The figure below shows the hammer set-up when driving horizontally. To counteract against the increased pressure in the gasbuffer, a constant tension (pull down force) is required to keep the hammerhousing fimly on the pile.
A spring arrangement is located between the tension-wires and the hammer to prevent too high shock loads in these wires.
Advantages of horizontal driving systems
There are a number of distinct advantages in using IHC and the Hydrohammers, when (large diameter) piles have to be installed horizontally:
- Easy to change configuration for different pile diameters.
(Only sleeve and anvil have to be replaced underneath the hammer).
- Faster tube installation progress.
- Standard Hydrohammers can be used, no modifications required.
- Extensive experience in driving large diameter piles
- Large rental fleet. Hammers available up to 600 kNm (450.000 ft.lbs) energy.
- Hammers available to very high rated energy levels (2300 kNm, 169.000 ft.lbs).
- Cleaner operation.
- Safer operation: working tool is outside, not inside the tube.
Field experience
In spring 2001, the Dutch contractor Ballast Nedam International (BNI) was awarded a job in Tampa, Florida, USA, to install a 3m diameter (10') casing with a length of 91m (300 ft) underneath a road and railway track.
After considering several options, the horizontal driving of a pile with a large impact hammer seemed to be the most optimal solution, both in terms of technology, time and costs.
The expected resistance to driving required a hammer with a rated energy of at least 90 kNm (66.000 ft lbs) being BNI's own IHC S-90 Hydrohammer.
First a test was carried out in Harderwijk, The Netherlands, driving a 42x1" pile 25 meters horizontally into a sand bed. Converting the measured resistance and energies to the situation in Florida (including the effects of friction reduction fluids to the internal and external circumference of the pile), the decision was taken to use the same S-90 hammer also for the Tampa job.
The total tunnel length was made up of 10 sections of 9.1 m (30'), coupled by a quick connect Permalok connection.
Although driving was harder than expected, the S-90 achieved a total distance of 8.5 sections (76m, 255'). Total blows given were close to 70.000.
After this job the hammer was sent to IHC's workshops and was completely disassembled.
No major wear was noticed on the upper and lower bearings of the ram and replacement of the bearings was not required.
On another job of BNI an IHC S-280 was used to drive another 3m (10ft) diameter casing.
