Pile Driving Monitoring (PDM) during driving and Pile Dynamic Testing (PDT) are widely used in onshore and offshore construction to ensure the structural integrity of the piles during driving and achieve a safe and economical pile installation. PDM helps in assessing the pile behaviour during installation and confirms the assumptions taken during pile design. In addition, it ensures that driving follows the established criteria and provides key elements for calculating the soil resistance during monitoring and system performance assessment.
Pile Driving Monitoring involves attaching strain gauges and accelerometers to the top of the pile. The striking of the pile with the hammer generates stress waves which travel along the pile shaft and mobilise the shaft friction and base pile resistance. Upward waves are then generated, travelling towards the pile head.
The incident and reflected waves are recorded through the sensors installed at the pile top and analysed, converting the strains into stresses and forces in the pile, while accelerations are integrated into particle velocities and displacements. The downward (incident) wave and the upward (reflected) wave can be isolated from the measured total waves at sensors level, knowing its Force and Velocity components. Pile’s ultimate bearing capacity or soil resistance under continuous driving can be estimated by an inversion process on the recorded reflected wave compared to the incident one. This is commonly known as Signal Matching methodology. The recorded Force and Velocity, integrated over time, are also used to compute the actual hammer energy transferred to the pile, providing information on driving system performance.