Development of a Wireless Monitoring System for Pile Driving

Over the past 5 years, the Florida Department of Transportation has been moving toward increased use of design-build, warranty, and contractor-recorded quality assurance and control information. With the additional desire to lower factors of safety in design, the industry is under pressure to monitor and record capacities, stresses, velocities, and the like for a greater percentage of piles driven on a site. The development of a disposable wireless pile monitoring system, which can be cast inside prestressed concrete piles, is described. The nonrecoverable portion of the system, which costs less than $350, consists of multiple pairs of accelerometers, strain gauges, analog-to-digital conversion circuitry, and a switchable wireless transmitter. A receiver located within 500 ft of the pile recovers strain and accelerometer data and sends it to a laptop computer, which then displays and analyzes the data in real time. The system has been tested both in the laboratory and in the field. Field testing consisted of monitoring two 0.61-m-diameter piles instrumented at the top and bottom with the wireless system as well as with externally attached instrumentation (current practice). Comparisons of capacities and stresses at the top of the piles for the new and existing systems were favorable. In addition, the new wireless system reported stresses and capacities at the bottom of the piles.