A Reusable Instrumented Test Pile for Improved Pile Design

Accuracy in estimating driven pile capacity at a particular site is limited due to an inability to capture the full complexity of the soil deposit, soil properties, pile drivability, dynamic soil/pile interaction, and pile setup. These potential errors are usually compensated by a safety factor. Development of an in situ testing device, which can replicate the construction condition to the greatest extent possible, to predict the pile capacity at the design phase of a project will result in economic benefits. A reusable instrumented test pile (RTP), which is an in situ testing device, is under development at University of California, Davis. RTP will be taken to field, assembled, driven into ground with a conventional Becker hammer rig, load tested, removed, and reused. The RTP consists of an instrumented tip and a series of 610 mm (24-in) long instrumented modules that are placed between conventional Becker hammer pipe (6.625-in diameter). The RTP instrumented modules are capable of measuring axial resistance, radial stress, temperature, acceleration, pore pressure and inclination. The measurements can be obtained during driving, load testing and setup. The multiple instrumentation clusters along the RTP pile length will provide insight into driving dynamics, installation energy required, tip to shaft bearing proportions, load transfer distribution along the pile shaft, end bearing capacity, and pile setup, among others. It is expected that these measures will improve pile performance predictions, ultimately resulting in foundation cost savings. The initial RTP design, development, and proof testing are presented.