Vibratory Hammer Mechanics
Vibratory Hammers are used to maintain synchronization and cancel horizontal vibration, paired eccentrics, powered by hydraulic motors, rotate in the gear case.
Vibration is transmitted into a driven pile by means of a hydraulic clamp attached to the bottom of the gear case.To prevent vibration from affecting the crane line which holds the vibratory hammer, a vibration suppresser is attached to the top of the gear case.Rubber elastomers dampen the vibration by up to 90%.
I.C.E. Hammer Frequencies
From our 20 years of experience we know that 1600 vpm combined with high eccentric moment will provide the most reliable, durable vibratory hammer. However, different jobs may require very different outputs for a variety of reasons. I.C.E. manufactures vibratory hammers in standard, high-frequency and low frequency units.
Standard Vibratory Hammer 1600 vpm
Low Frequency/Light weight Hammer 1200 vpm
High Frequency Vibratory Hammer 2300 vpm
Our range of vibratory hammers meets the needs of contractors for any type of job from low vibration to low cost.
Glossary of Terms
The force genrated by rotating eccentrics. Small increases in speed can cause large increases in centrigugal force with no corresponding increase in capability. This force is generally measured in tons or Nm.
|Vibrating weight||A vibrating weight is a suspended weight on a pile. This is usually measured in lbs or kg.|
|Engine power||Vibratory Hammers must be able to be powerful enough to master the friction between pile and soil. A power unit with low output will not allow the vibtrator to overcome this skin friction. Measurement of this the power output is usually in HP or kW.|
|Eccentric moment||A key factor in vibrator performance is eccentric moment. The eccentric moment must create enough amplitude to exceed the elastic range of the soil. If moment increases than amplitude also increases. Conversely, more pile weight will decrease amplitude. This is usually measured in in-lbs or kg-m.|
|Amplitude||The vertical travel of pile per vibration.|
|Line pull for extraction||Line pull is the amount of pull a suppresser can handle before engaging safety stops. In order for this to work properly, the crane must be able to pull at a radius. This is usually measured in tons or kN.|
|Frequency||Vibrations Per Minute (vpm) and speed of rotating eccentrics|
|Suspended weight||Total weight of vibrator = gear case, suppressor, clamp, typically 1/2 the weight of the hydraulic hoses and any additional bias weight or other special additions. This is typically measured in lb or kg.|
|Non-vibrating weight||Weight of the non-vibrating parts of the vibrator, including any added weight. This is typically measured in lb or kg.|
|Clamping force||Hydraulic pile clamping force provided by clamp(s). This is typically measured in tons or kN.|
Uses of Vibratory Hammers in Different Soil Conditions
Soil liquidation occurs next to the pile causing the soil particles to their “grip” on the pile. The pile moves downward under its own weight, plus the weight of the vibrator. Adding additional non-vibrating weight can usually aid driving. Vibratory Hammers are usually very effective on non-displacement piles such as sheet piling, H-beams, and open-end pile or caissons but less effective for displacement piles such as concrete, timber, and closed-end pipe.
2. In cohesive soils
Cohesive soils require the vibration to break the soil-to-pile adhesion, allowing the pile to move downward. With less amplitude, the soil will simply move with the pile. The soil under the pile tip must also be pushed out from under the pile. This occurs more easily with non-displacement pile than with displacement piles. Adding additional non-vibrating weight aids driving in cohesive soils.
3. For extracting piles
A vibrator is effective for extracting piles since the resistant soil during driving under the pile tip does not have to be moved.
4. For soil compaction of granular soils
A vibrator works well for soil compaction in granular soils because the soil disturbance caused by vibration causes the soil particles to move into a denser configuration.
For more information on ICE Pile Driving Equipment