Ground-Borne Vibration can be a serious concern for any building or structure within or adjacent to a construction zone. These structures may be potentially impacted by vibrations emanating from construction activities such as demolition, compaction, excavation, blasting, pile-driving, and operating heavy earth-moving equipment. In extreme cases, the vibration can cause damage to adjacent buildings and create discomfort and annoyance for building occupants. This is a particular concern to heritage structures and vibration-sensitive facilities such as hospitals, research laboratories, MRIs, and laser eye technology centers. This article provides a brief review to Ontario Building Code, with respect to Regulation of Vibrations from Construction Activity.
Monitoring of Vibrations during Construction
As part of the Ontario Building Code, Toronto is one of the first cities in North America that mandates Assessment of Construction-Related Vibrations to ensure that minimum building standards are met. This regulation aims to minimize adverse effects of ground-borne vibrations on adjacent buildings and structures within the “Zone of Vibration Influence”.
Construction activity shall not be carried on when the records show the measured vibration exceeds the Prohibited Construction Vibration Levels set out in Table below.
Frequency of Vibration – “The rate of oscillation that occurs in one second, measured in hertz where one hertz equals one cycle per second.”
Vibration Peak Particle Velocity – “The maximum rate of change with respect to time of the particle displacement, measured on the ground, and velocity amplitudes are given in units of millimeters per second from zero to peak amplitude.”
Zone of Vibration Influence
To prevent unnecessary disputes between developers and residents, an assessment can be undertaken prior to construction activities to identify the area surrounding the site that may be subject to vibrations (Zone of Vibration Influence). This study will determine the number of existing structures that need to be surveyed by way of a pre-construction inspection for existing flaws such as foundation cracks, drywall cracks, etc. before construction begins and/or identify the number of houses, if any, that require vibration monitoring during construction.
There are various parameters that are involved in identifying the zone of influence which should be identified by a professional engineer. Examples include:
- The precise location of the source of vibration
- Soil conditions of the construction site and adjacent land
- Whether the proposed construction will be above or below the water table
Zone of Influence – “The area of land within or adjacent to a construction site, including any buildings or structures, that potentially may be impacted by vibrations emanating from a construction activity where the peak particle velocity measured at the point of reception is equal to or greater than five mm/sec at any frequency or such greater area where specific site conditions are identified by the professional engineer.”