Construction activities create special vibration challenges. Proximity of construction to adjacent neighbors means increased neighbor awareness and a constant visual focus. Standard monitoring alone may not be adequate to diminish fear of damage. More advanced monitoring from GeoSonics/Vibra-Tech can demonstrate compliance to limits and show the reaction of buildings to outside activity.
Project:
Dooleymack Constructors, one of the southeast's premier construction firms, was selected to build a nursing home in South Florida. Construction activity for the new building was adjacent to a private school. Operations included site preparation, steel sheet pile driving, excavation of subsurface materials, and foundation construction. Given the potential for claims from vibration and construction, GeoSonics/Vibra-Tech was retained for vibration monitoring and pre-construction inspections.
Initial Services:
GeoSonics/Vibra-Tech initially provided inspection services on surrounding buildings. With federal funding involved, delays required re-inspection of the buildings nearby to compare for changes due to environmental effects. Once the inspections were completed, we set up Re:mote seismographs for long-term monitoring.
Re:mote seismographs were initially set up to monitor normal vibration from pile driving and construction operations. During the initial driving, vibration levels measured were over the warning threshold and piles were not being driven to depth. Although soil borings indicated limited rock, the actual site had excessive rock that refused the driving of the steel sheet pile. When alternate drilling was conducted prior to the piles being driven, the contractor received complaints from the adjacent school. For immediate feedback, GeoSonics/Vibra-Tech technicians were on site during all close proximity drilling and pile driving to measure and provide caution-level information to the contractor. Additionally, both on-site and Re:mote seismographs and field technicians provided technical information to maintain ground vibration below limits for structures.
Problem:
Two weeks after completion of initial pile driving, an inspection revealed soil settlement, indicated by the cracking of the south wall of one building. Roots and debris in the area of wall support indicated prior problems with the foundation. While not related to the ground vibration directly, the contractor completed repairs, and support to the foundation was reestablished.
During the final phases of pile driving and foundation preparation, the company needed a method to monitor existing cracks and verify that those observed on the south wall were not changing.
Solution:
To address this challenge, GeoSonics/Vibra-Tech combined on-site vibration monitoring by our expert technicians with Re:mote crack monitoring stations. Two crack monitoring units were established to follow crack expansion and contraction trends on four individual cracks. Units tracked the cracks 24/7 for two months during and after pile driving. Crack data was reviewed by GeoSonics/Vibra-Tech technicians daily to check for movement. Data trends showed that the cracks were subject to normal environmental movement, opening and closing daily, while vibration levels had little to no effect. In fact, environmental movements were significantly greater due to temperature and humidity. Daily cycling indicated that no permanent movement was occurring. Successful vibration monitoring combined with crack motion evaluation allowed the project to be completed without further problems.
