Why are vibrations monitored? What are the types and sources of construction vibration? How are vibrations reported?
Reasons for Monitoring Construction Vibration
Avoid excessive vibrations that can lead to property damage, litigation, project delays, and increased costs
Inform construction engineers of excessive vibrations so they can take mitigating actions
Provide documentation for regulatory agencies
Help resolve damage claims
Sources of Construction Vibration
- Impact pile driving
- Dynamic compaction
- Pneumatic tamping
- Vibratory Compaction
- Vibratory Pile Driving
- Excavation Machinery
- Pavement Milling & Rubblizing
Reporting Construction Vibration
- Ground vibration propagates in waves.
- The wavefronts cause particle motion.
- Vibration monitors measure the velocity and frequency of particle motion.
- Velocity is reported in inches per second. Higher velocities are more damaging.
- Frequency is reported in Hz. Lower frequencies are more damaging.
Vibration Limit Chart
- The limit chart plots particle velocity against frequency.
- Points falling above the limit line are considered potentially damaging.
- Points falling below the limit line are considered non-damaging.
- The limit chart was developed for transient vibrations (blasting). Limits for continous vibrations are typically 2 to 5 times more restrictive.
Histogram & Waveform Event Reports
- The histogram report, useful to demonstrate that the site is actively monitored, shows the peak particle velocity measured during successive time periods.
- The waveform event report shows a single event, typically triggered by a limit exceedance.