Automated monitoring confirms movement during pile driving
For a bridge-piling project for the Minnesota Department of Transportation at the Cayuga Interchange in Saint Paul, Lunda Construction hired Barr to provide monitoring services for a 66-inch sanitary sewer line. The project itself entailed pile installation for new bridge-pier foundations. Excavations for the piers were as close as 8 feet from the sewer centerline.
We attached prisms to the sewer line as well as a steel-girder frame and timber wall supporting the excavation wall. The prisms allowed continuous near–real time monitoring during both pile installation and construction downtimes. The automated motorized total station (AMTS) was positioned for optimal vantages of the construction site, reducing the need for repositioning. When line of sight was limited between the AMTS and prisms, Barr used the onboard camera to troubleshoot issues remotely. Over 10 months, any challenging schedule and weather conditions were handled successfully without the need for site visits.
In addition to AMTS displacement monitoring, Barr deployed and remotely monitored vertical displacement using two horizontally installed ShapeAccelArrays positioned along the exposed sewer line. The difference in vertical displacement between the two systems was calculated at 5/32 inches.
Barr reviewed and interpreted the data, which was managed in a database, and relayed information to the client via text, phone, and emails. As a result of the data, we issued several stop-work orders. During active construction, we monitored data more frequently to help maintain public safety.