Construction activities like utility structure removals, demolition, excavations, compaction, and asphalt placement can generate ground vibrations that have the potential to disturb surrounding structures, and in the case of Arlington Cemetery, monuments, and gravestones. It is something most people do not think about, but what happens when construction activity occurs in and around important national landmarks?
When structures need protecting, a vibration monitoring plan is created and implemented to reduce the potential for disturbance of these structures. At Arlington National Cemetery, ECS has provided this vibration monitoring service on two recent roadway and stormwater improvement projects.
To start, ECS’ structural engineer reviewed the condition of monument features within 100 feet of the proposed construction to identify which features could be sensitive to vibration. Then a vibration attenuation study was performed to evaluate what types of construction equipment and operations had the potential to produce impactful vibrations. This study allowed ECS to better understand what magnitude of vibration could be expected to be generated from the construction activity and how that vibration dissipated with distance aiding us to understand what a potential safe distance would be between the construction activity and the sensitive features. A series of vibration monitors were then installed along the roadway alignments between construction activity and the sensitive structures. Baseline measurements were taken so that the team could understand existing ambient vibration levels prior to construction and allow the team to compare those levels against construction-related vibrations.
While the roadway construction occurred, vibration levels were monitored in real-time. Each vibration monitor was equipped with a solar panel and a cellular modem and programmed to provide an email notification to the project team when a project-defined warning threshold as prescribed by the project specifications was exceeded. Following these notifications, detailed data reports were shared that showed where and to what level the vibration was occurring and whether the vibration was judged to be related to nearby construction activities. The team used this information along with continued visual observations of the features to assess for potential signs of damage or disturbance. This information allowed the construction team to make judgements on what equipment could be used and how it could be safely used on the project.
As the project progressed, the monitors were re-located as necessary along the alignment with emphasis on portions of the alignment near tall, aged, and cracked monuments and gravesite headstones. This monitoring continued through completion of the final paving of the new roadway alignments.