Book excerpt: "Caltrans' investment in driven piling to support bridges and other structures has averaged about $25M/year over the last decade. The systems constructed have performed well, but conservatism exists due to uncertainties in soil properties, pile drivability, soil-pile interaction, and pile setup. A new method that could achieve modest saving of 5% in design could save in excess of $1M per annum. This report presents the development of a reusable instrumented test pile (RTP) as an in situ testing device for improved pile design in granular soils (coarser than No. 200 sieve). The RTP system consists of short instrumented sections that provide measurements of axial load, radial stress, pore pressure, and acceleration, and are connected in series with standard Becker pipe sections. The RTP - Becker pipe string is driven using the standard Becker pile driving hammer, and the TRP system was designed to handle the high installation stresses in granular soils while retaining sufficient resolution in the instrumentation readings for subsequent analyses of shaft and tip resistances. RTP measurements obtained during driving provide detailed information regarding pile drivability, measurements during static tests capture load transfer along the pile, and measurements during pile setup capture capacity gain over time. The design, fabrication, calibration, proof testing, and full scale field deployment are presented herein." -- Technical report documentation page