Breaking road surfaces
The most common tool used to break up road and pavement surfaces is the hand-held percussive breaker. These tools typically produce hand-arm vibration magnitudes of between 5 and 20 m/s2 with an average of around 12 m/s2. A full-time breaker operator working on a road excavation job might be exposed to this vibration for an average of 3 hours per day which would give a typical exposure of 7 m/s2 A(8) which is above the exposure limit value. The amount of work that an operator can do with one of these tools in a day varies depending on the depth and hardness of the surface to be broken up.
In some circumstances it is possible to greatly reduce the vibration exposure by using a larger breaker attachment mounted on the arm of an excavator. This method was used by a utilities contractor for digging telecommunications trenches in the road in a busy urban area. There was already an excavator on site for digging out the trenches once the surface had been broken, and the bucket was replaced with a breaker attachment, which took about 5 minutes, whenever required. The breaker is powered using the excavator hydraulics and is activated by a foot pedal. The arm position is controlled by a pair of levers, passing very little vibration (vibration magnitude is less than 1 m/s2) to the operator’s hands. A hand-held breaker, fitted with a sharp cutting tool, was used for about 5 minutes at the beginning of the day to score the edges of the area to be broken up with the mounted breaker.
Mounted breaker being used to break roadway
- This method reduces the time the operators are exposed to vibration. The exposure for the hand-held breaker operator was reduced to little more than 1 m/s2 A(8).
- On the type of surface found in this example, the mounted breaker works approximately 10 times as fast as one person with a hand-held tool.
- The attachments on the excavator can be changed very quickly.
- Overall there is less disruption and noise.
- Tunnelling and Pipejacking: Guidance for Designers
- Pile cropping. A review of current practice
- Hand-arm vibration at work: A brief guide